2.02 Processing of Alumina and Corresponding Composites

Absolute Z ero The lowest achievable temperature of 0 Kelvin or −273C.Accuracy How close data come to the accepted or “real” value.Actinides Elements with the atomic numbers 90 through 103.Activation Energy The energy needed to start a reaction.Alcohols Organic compounds that have the function group R—OH.Alkali Metals Group 1 metals of the periodic table.Alkaline Earth Group 2 metals of the periodic table.MetalsAlkanes Saturated hydrocarbons that contain all single bonds.Alkenes Unsaturated hydrocarbons that have a double bond between twocarbons.Alkyl Halides Class of organic compounds in which a halogen is bonded to the organic molecule.Alkynes Unsaturated hydrocarbons that have a triple bond between twocarbons.Allotropes Different substances in the same phase formed from the same elements. Alpha Particles Particles containing two protons and two neutrons. These particles are identical to helium-4 nuclei. The symbols are 42He or .Amides Organic compounds that have the function group R—CO—NH2.Amines Organic compounds that have the function group R—NH2.Amphoteric Describes a substance that can act as either an acid or a base.Anion A negatively charged ion.Anode Electrode where oxidation occurs.Artificial A nuclear reaction in which an isotope is being bombarded with a Transmutation particle to trigger the transmutation.Atom Composed of protons, neutrons, and electrons, an atom is a particlethat defines an element.Atomic Mass The atomic mass takes into account all the masses of the isotopes of an atom and their relative abundance.Atomic Number Number of protons located in the nucleus of an atom. Can also be defined as the nuclear charge of an atom.Atomic Radius The distance from the atom’s nucleus to the outermost electron of that atom.Atomic Theory Theory of the atom as stated by John Dalton: All matter is composed of atoms; all atoms of a given atom are alike; compounds are made up ofatoms combining in fixed proportions; a chemical reaction involves the rearrangement of atoms; and atoms are neither created nor destroyedin a chemical reaction.Avogadro’s Number One mole, or 6.02 1023.Beta Particle An electron that is ejected from the atom’s nucleus.Binary Compounds Compounds that have only two different elements present. Boiling Point The point at which the vapor pressure of a liquid is equal to the surrounding/atmospheric pressure.Boyle’s Law A gas law stating that at constant temperature, pressure and volumehave an inverse relationship.Buffer A solution that is resistant to changes in pH.Calorie A measure of heat energy; 1 calorie is equal to 4.18 joules.Carbonyl Group Part of an organic compound characterized by the double bondbetween a carbon atom and an oxygen atom, C O.Cathode Electrode that is the site of reduction.Cation An ion with a positive charge.Celsius A measure of temperature in which the freezing point of water is 0 Cand the boiling point of water is 100 C.Chain Reaction Reaction in which one event causes multiple events to occur until all materials have been consumed.Charles’ Law A gas law stating that at constant pressure, temperature and volume are directly proportional.Chemical Formulas An expression of the composition of a compound by a combination of symbols and figures that show which elements are present and howmuch of each element is in a compound.Chemical Properties Properties that are observed with regard to how a substance reacts with other substances.Coefficient Numerical indication of the quantity of a substance in an equation.Colligative The properties of a solvent that depend on the concentration ofProperties dissolved particles present.Combined Gas Law A gas law that combines the laws of Charles and Boyle.Common Ion Effect A decrease in the solubility of a salt due to the shift in equilibrium when an ion is added to the solution.Compound Two or more elements combined with definite proportions.Conjugate Acid The acid formed when a Bronsted-Lowry base gains a proton.APPENDIX 5 / GLOSSARY 297Conjugate Base The base formed when a Bronsted-Lowry acid loses a proton.Conjugate Pair An acid or base that differs only in the presence or absence of a proton. Conservation The sum of the charges of the reactants will be equal to the sum of theof Charge products.Coordinate A covalent bond in which one atom donates both electrons.Covalent BondCovalent Bond A bond formed when two nonmetal atoms share electrons in order to satisfy their need to have a full outermost principal energy level.D alton’s Law of A law stating that the combined pressure of a combination of gases is Partial Pressures equal to the sum of the individual pressures of the gases.Decay Series Series of decays an isotope will undergo until a stable isotope is formed. Decomposition The process by which one compound breaks down into many substances. Density Mass per unit of volume.Deposition Changing from the gas phase to the liquid phase without any apparentsolid phase in between.Dipole The condition in which a molecule ha s a “buildup” of negative chargeon one side and a positive charge on another side.Dispersion Forces Weak forces existing between nonpopular molecules. Also known as Van der Waals forces.Double Bond A covalent bond that involves the sharing of two pairs of electrons.Double Reaction in which two elements exchange anions and cations to form Replacement the products.Ductile Has the ability to be rolled into thin wires.Electrode Potentials Voltage of a given oxidation or reduction half reaction.Electrodes Sites for oxidation and reduction.Electrolysis A reaction in which electricity is used to make a nonspontaneousreaction occur.Electrolyte A solute that creates ions in solution that can carry an electrical current. Electrolytic Cell A device that requires an outside source of current to make a nonspontaneousreaction occur.Electron A negatively charged particle that orbits the nucleus of an atom in theprincipal energy levels.Electronegativity A measure of an atom’s ability to attract electrons.Electroplating Coating a substance with a metal.Element A substance that is unable to be broken down chemically.Empirical Formula Shows the lowest ratio of all the elements of a compound to each other. End Point Point of a titration where the indicator changes color.298 APPENDIXESEndothermic When more energy is absorbed than released in a chemical reaction.Energy The ability to do work.Enthalpy The heat absorbed or released in a chemical reaction. Also known asthe heat of reaction.Entropy Used to describe chaos, randomness, and disorder.Equilibrium A state of balance between two opposing reactions that are occurring atthe same rate.Ethers Organic compounds that have the functional group R—O—R.Excess Reagent The compound that does not completely react in a chemical reaction. Excited State The movement of electrons to a higher energy level once energy hasbeen added to an atom.Exothermic Describing a chemical reaction in which more energy is released than absorbed.Families The vertical columns on the periodic table.Faraday The charge of one mole of electrons. A charge of approximately96,500 coulombs.Filtrate The aqueous portion of a sample that has been poured throughfilter paper.Fission The splitting of larger nuclei into smaller ones, causing a release ofnuclear energy.Freezing The process by which particles of the liquid phase enter the solid phase.Functional Groups Particular arrangement of atoms in organic compounds.Fusion The joining of smaller nuclei to form a larger one, causing a release ofnuclear energy.Gamma Rays High-energy electromagnetic radiation emitted from the nucleus of a radioactive atom.Gas A phase of matter characterized as having no definite volume or shapeand having molecules spaced far apart.Geiger Counter A device used to detect and measure the activity of radioactive particles. Gibbs Free Energy Equation used to determine if a reaction will be spontaneous. Graham’s Law At the same temperature and pressure, gases effuse at a rate inversely proportional to the square roots of their molecular masses.Ground State When the electrons are in their lowest energy state.Group Vertical column on the periodic table.Half Cell Part of a voltaic cell where oxidation or reduction can occur.Half-Life The amount of time it takes for half a radioactive substance to decay.Half Reactions Two separate reactions that show the oxidation and reduction reactions separately.Halogens Elements found in group 17 of the periodic table.APPENDIX 5 / GLOSSARY 299Heat of Reaction The heat absorbed or released in a chemical reaction. Also known as enthalpy.Hess’s Law The sum of the heats of reaction of the steps in a reaction is equal to the overall heat of reaction.Heterogeneous Describing a mixture that is not the same throughout.Homogeneous Describing a mixture that is the same throughout.Hund’s Rule Electrons will fill an orbital singly to the maximum extent possiblebefore pairing up.Hybridization The promotion of an electron to a higher energy level so that the atom can bond to another atom.Hydrocarbon An organic compound that consists of only the elements hydrogen and carbon.Hydrogen Bonding A weak force that comes about when hydrogen is bonded to fluorine, oxygen, or nitrogen.Hydrolysis The addition of water to a salt to form the acid and base from which thesalt was made.Ideal Gas Law A law that states that an ideal gas obeys the equation PV nRT. Indictors Substances that change color to indicate if a substance is acidic orbasic.Intermolecular A bond that exists between molecules.BondIntramolecular A bond that exists between atoms.BondIon An atom that has gained or lost electrons.Ionic Bonds Very strong bonds that are formed between a cation and an anion.Ionization Energy The energy needed to remove an electron from an atom to form an ion. Isomers Compounds with the same molecular formula but different structures. Isotopes Atoms that have the same atomic number but a different mass numberdue to having a different number of neutrons.Joule A measure of heat energy. 4.18 Joules is equal to 1.0 calories.Kelvin The Kelvin scale is based upon the lowest temperature that can beachieved, 0 K (absolute zero) or −273 C.Kinetic Energy Energy that is in motion.Kinetic Molecular Set of rules that are assumed to govern the motion of molecules. TheoryLanthanides Elements with the atomic numbers 58 through 71.Lattice Regular structure among the atoms in a solid.Law of Conservation The law stating that mass cannot be created or destroyed in aof Mass chemical reaction.300 APPENDIXESLe Chatelier’s When a stress or change in conditions is applied to a system at Principle equilibrium, the point of equilibrium will shift in such a manneras to relieve the applied stress.Lewis Structure A drawing of the structure of a compound in which the arrangement of the valence electrons is represented by the use of dots.Limiting Reagent Substance that is completely used up in a chemical reaction.Line Spectrum Specific wavelengths of light emitted from an atom when the electrons return to the ground state from the excited state.Liquids Have a definite volume, take the shape of the container they are placedin, and have touching molecules.Litmus Indicator that turns red in acid and blue in base.Malleable Has the ability to be hammered into thin sheets.Mass Measure of the quantity of particles in an object.Mass Action An equation written that shows the product of the concentrations of the Equation products raised to the power of their coefficients divided by the productof the concentrations of the reactants raised to the power of theircoefficients is equal to a constant.Mass Def ect The amount of mass of the particles involved in the nuclear reactionthat is converted to energy.Mass Number The total number of nucleons (protons and neutrons) found in an atom. Matter Anything that has mass and takes up space.Melting Particles of the solid phase entering the liquid phase.Melting Point The temperature at which the particles of the solid phase enter theliquid phase.Meniscus The curvature of a liquid that is the result of the adhesive forcesbetween the liquid’s molecules and the walls of a glass container.Metallic Bond A bond in which the electrons are free to move among the metal atoms. Metalloids Elements that exhibit some of the properties of metals and nonmetals. Metals Elements that are characterized by the ability to conduct heat andelectricity, have a shiny luster, and lose electrons in a chemical reaction.Mixtures The result of combinations of elements and/or compounds.Molality Way of expressing concentration. Ratio of moles of solute to kilogramsof solvent.Molar Volume Volume (22.4 liters) that one mole of a gas will occupy at STP.Molarity Way of expressing concentration. The ratio of moles of solute to totalliters of solution.Mole A unit of Avogadro’s number. A mole of particles is equal to 6.02 1023of those particles.Mole Ratio The ratio of the number of moles of one substance to the moles ofanother substance as dictated by the balanced equation.APPENDIX 5 / GLOSSARY 301Molecular Formulas Indicate the total number of atoms of each element that are present in a covalently bonded molecule.Molecule-Ion Attraction between charged ions and polar molecules in a solution. AttractionNatural Transmutation that does not need to be triggered by a particleTransmutation bombarding the isotope.Network Solid Nonmetal atoms bonding to each other in a covalent fashion to form a continuous network.Neutralization The process in which an acid and a base react to form salt and water. Neutron A particle with no charge that is found in the nucleus of an atom.Noble (Inert) Gases Gases found in group 18 of the periodic table.Nonmetals Elements that are characterized by being poor conductors of heat and electricity, being soft and brittle, and tending to gain electrons to formanions.Nonpolar Covalent A covalent bond in which the electrons are shared and distributed Bond equally.Nucleons Particles found in the nucleus of an atom (protons and neutrons).Octet Rule An atom will desire eight electrons in its outermost principal energylevel to maximize its stability.Orbital Region around the atom where electrons are most likely to be found.Organic Chemistry Study of carbon and carbon-containing compounds.Oxidation A loss of electrons.Oxidation Number The charge on an ion or the charge that an atom “feels.”Oxidizing Agent The reducing substance that causes the oxidation of other substances. Pauli Exclusion A rule that states there cannot be more than two electrons in an atomic Principle orbital. It also states that no two electrons can have the same fourquantum numbers.Percent Ratio of the total mass of an element in a compound to the total mass Composition of the compound.Period Horizontal row on the periodic table.pH Negative logarithm of the hydrogen ion concentration of a solution.Phenolphthalein Indicator that is colorless in acid, and pink (or purple, magenta) in base.Physical Properties Observable and measurable properties of a substance.Pi Bond The second or third bond that is formed between hybridized atoms thathave orbitals which overlap.Polar Covalent Bond A covalent bond that involves electrons not being shared equally. Polyatomic Ions Ions that have many atoms in them.Positron A particle that has the same mass as an electron but a charge of 1.Potential Energy Energy that is stored.302 APPENDIXESPrecipitate An insoluble substance that separates from, and forms in, a solution. Precision How close results from the same experiment agree with one another. Pressure The measurement of the ratio of the force exerted on an area.Products The results of a chemical reaction.Proton A particle found in the nucleus of an atom with a positive charge.Quarks Subatomic particles that make up protons and neutrons. Quarks have charges of 2/3 or −1/3.Rate Change in concentration over time.Reactant A substance used at the start of an equation.Redox Another term for oxidation and reduction.Reducing Agent The oxidized substance causing the reduction of other substances. Reduction A gain of electrons.Residue The solids that are trapped by filter paper.Reversible A reaction in which products formed further react to form the original Reaction reactants.Row s Horizontal rows on the periodic table.Salt Bridge An apparatus that allows ions to migrate from one half cell to another. Saturated Describing a solution in which a dissolved solute and an undissolved solute are in equilibrium.Semimetals Elements that exhibit some of the properties of metals and nonmetals. Sigma Bond A bond that arises from the overlap of two s orbitals or from the overlap of one s and one p orbital.Single Replacement Reaction where one element replaces another element.Solids Substances that have definite shape and volume. The atoms are in arigid, fixed, regular geometric pattern.Solubility The ability of a substance to dissolve in another substance.Solubility Product The equilibrium constant of a slightly soluble salt.ConstantSolute A substance that is dissolved into a solvent.Solution A homogenous mixture of a solute and a solvent.Solvent A substance that a solute is dissolved into.Spectators Substances that do not take part in a reaction.Spontaneous A process that occurs without added external energy or without additional intervention.Standard Pressure Pressure characterized by pressures equal to 760 mm Hg, 760 torr, 101.3 kPa, or 1.0 atm.APPENDIX 5 / GLOSSARY 303Standard A common standard of conditions, defined as 0 C and 1 atm Temperature (273 K and 760 torr).and PressureStock Method Method for naming compounds where a roman numeral is used to indicate the amount of positive charge on the cation.Stoichiometry The branch of chemistry that deals with the amounts of products produced from certain amounts of reactants.Sublimation Changing from the solid phase to the gas phase without any apparent liquid phase in-between.Substance A variety of matter with identical properties and composition. Supersaturated When a solution contains more solute than a saturated solution would at a given temperature.Symbol Letter(s) designation for an element.Synthesis When many substances come together to form one compound. Temperature Average kinetic energy possessed by a sample.Titration The process by which acids and bases can be measured out in exact quantities so that they neutralize each other exactly and without anyexcess.Transition Metals Metals found in groups 3 through 10 of the periodic table. Transmutation Formation of a new element when an element undergoes nuclear disintegration.Triple Bond A covalent bond that involves the sharing of three pairs of electrons. Triple Point A specific point in temperature and pressure at which solid, liquid, and gas exist at the same time.Unsaturated Describing a solution that contains less solute than a saturated solution would at a given temperature.Valence Electrons The electrons that are located in the outermost principal energy level. Van der Waals Weak forces existing between nonpolar molecules. Also known as Forces dispersion forces.Vapor Pressure Pressure exerted by the vapor of a liquid as the molecules of the liquid evaporate.Vaporization Process by which a liquid enters the gas phase.Voltaic Cell A setup that allows a redox reaction to occur spontaneously so that the electrons can be used to do work.Volume The space an object occupies.。

铝合金的英文书籍Aluminum Alloys Handbook by George E. TottenAluminum alloys play a crucial role in modern manufacturing and engineering applications due to their lightweight, high strength, and corrosion resistance properties. For those looking to deepen their understanding of aluminum alloys, "Aluminum Alloys Handbook" by George E. Totten is a comprehensive resource that covers a wide range of topics related to the development, processing, and applications of aluminum alloys.This book provides a thorough overview of the history and development of aluminum alloys, including their composition, microstructure, and mechanical properties. It also delves into the various processing techniques used to fabricate aluminum alloys, such as casting, extrusion, and forging. The author, George E. Totten, is a renowned expert in the field of materials science and engineering, and his expertise shines through in the detailed explanations and insights provided in this book.One of the key strengths of "Aluminum Alloys Handbook" is its coverage of the practical applications of aluminum alloys in different industries, including automotive, aerospace, and construction. The book explores the unique properties of different aluminum alloy compositions and how they can be tailored to meet specific performance requirements. Additionally, it discusses the latest advancements in aluminum alloy technology, such as the development of new alloy compositions and processing techniques.Whether you are a student, researcher, or industry professional, "Aluminum Alloys Handbook" is a valuable resource that will enhance your knowledge and understanding of aluminum alloys. The book is well-organized and easy to follow, making it accessible to readers with varying levels of expertise in the field. With its in-depth coverage of the subject matter and practical insights, this book is a must-have for anyone interested in the science and engineering of aluminum alloys.In conclusion, "Aluminum Alloys Handbook" by George E. Totten is an authoritative and comprehensive guide to the world of aluminum alloys. Its detailed explanations, practical insights, and coverage of the latest advancements in the field make it an invaluable resource for anyone seeking to expand their knowledge of this important material. Whether you are a student, researcher, or industry professional, this book is sure to deepen your understanding of aluminum alloys and their diverse applications.。

Unit 2 Classification of MaterialsSolid materials have been conveniently grouped into three basic classifications: metals, ceramics, and polymers. This scheme is based primarily on chemical makeup and atomic structure, and most materials fall into one distinct grouping or another, although there are some intermediates. In addition, there are three other groups of important engineering materials —composites, semiconductors, and biomaterials.译文：译文：固体材料被便利的分为三个基本的类型：金属，陶瓷和聚合物。

固体材料被便利的分为三个基本的类型：金属，陶瓷和聚合物。

固体材料被便利的分为三个基本的类型：金属，陶瓷和聚合物。

这个分类是首先基于这个分类是首先基于化学组成和原子结构来分的，化学组成和原子结构来分的，大多数材料落在明显的一个类别里面，大多数材料落在明显的一个类别里面，大多数材料落在明显的一个类别里面，尽管有许多中间品。

尽管有许多中间品。

除此之外，此之外， 有三类其他重要的工程材料－复合材料，半导体材料和生物材料。

有三类其他重要的工程材料－复合材料，半导体材料和生物材料。

Composites consist of combinations of two or more different materials, whereas semiconductors are utilized because of their unusual electrical characteristics; biomaterials are implanted into the human body. A brief explanation of the material types and representative characteristics is offered next.译文：复合材料由两种或者两种以上不同的材料组成，然而半导体由于它们非同寻常的电学性质而得到使用；生物材料被移植进入人类的身体中。

Chapter 3 Processing Technology3.1 Crystal growth and epitaxy晶体生长和外延As discussed previously in Chapter 1, the two most important semiconductors for discrete分离的devices and integrated circuits are silicon and gallium镓arsenate砷酸盐.正如之前在第一章所讨论的，对于分立器件和集成电路而言, 两种最重要的半导体是硅和砷化镓。

In this chapter we describe the commontechniques for growing single crystals of these two semiconductors.在本章, 我们描述生长这两种半导体单晶的常用技术。

The basic process flow is from starting materials to polished抛光wafer s.基本流程是从原料到抛光片。

The starting materials (e.g., silicon dioxide for a silicon wafer)are chemicallyprocessed to form a high-purity polycrystalline 多晶semiconductor from which single crystals are grown.原材料(即，用于生长硅片的二氧化硅) 通过化学处理形成高纯度的多晶半导体以生长单晶。

di-ox-ide二-氧-化物di-chlor-ide二-氯-化物di-sulf-ide 二-硫-化物poly crystal line多晶前缀poly-聚合、多, mulit-多single- 单singl-walled (layer)The single-crystal ingot s锭are shaped to define the diameter of material and saw ed into wafers.定形后的单晶锭决定了材料的直径，并且被切成晶元。

The Chemistry of Alloys and TheirApplicationsAlloys are materials that are formed by the combination of two or more metallic elements. The combination of these elements, along with the process by which they are combined, gives rise to a new material with enhanced properties that cannot be found in the individual elements that make it up. These properties depend on the composition, microstructure and thermomechanical processing of the alloy. Alloys find applications in a wide range of products, ranging from the manufacture of aircraft and automobiles, to the production of medical devices, construction materials and household appliances.The chemistry behind alloys is complex and involves a careful balancing of the amounts of the constituent elements, as well as the specific crystal structure that forms when they are combined. The elements that are combined in an alloy can be categorized into two main types: base metals and alloying elements. Base metals refer to the metallic elements that form the bulk of the alloy, while alloying elements are added in smaller quantities to modify the properties of the alloy.The atomic structures of the constituent elements determine whether the alloy will be a solid solution, a compound or an intermetallic compound. Solid solutions arise when the constituent elements have similar crystal structures, but differ in atomic size. Such a difference forces the crystal structure to distort in order to accommodate the smaller or larger atoms. The distortion allows the constituent atoms to be homogeneously distributed throughout the alloy, resulting in a material with superior properties than those of the individual constituent elements.On the other hand, compounds are formed when the constituent elements have different crystal structures and their atomic sizes differ significantly. Compounds have a predictable atomic arrangement, called a crystal structure, based on the identity and concentration of the constituent elements. Intermetallic compounds have a more ordered crystal structure than compounds, and are not homogeneously distributed in the alloy.Alloying elements have a profound effect on the properties of the resulting alloy. For example, the addition of chromium to iron forms stainless steel, which is resistant to corrosion and is therefore used in the production of medical devices, household appliances, and infrastructure materials. Similarly, the addition of magnesium to aluminum forms a strong, lightweight alloy that is used in the manufacture of aircraft and automobiles.Another aspect of alloys that is important is the process by which they are formed. The most common methods for forming alloys are casting, forging and extrusion. Casting involves the pouring of the alloy into a mold and allowing it to cool, while forging involves the heating and shaping of the alloy by hammering or pressing. Extrusion is a process whereby the alloy is passed through a die that shapes it into the desired shape, while simultaneously applying heat to improve its properties.In conclusion, the chemistry of alloys and their applications is a fascinating topic. The combination of different metallic elements gives rise to a material with unique properties and applications that cannot be achieved with the individual elements. The chemistry behind alloys involves a careful balance of the constituent elements, as well as the specific crystal structure that forms when they are combined. The resulting alloy can be formed through various methods, including casting, forging and extrusion. Alloys find applications in a wide range of products, and their use is set to increase as new technologies and developments arise.。

CONTENTSPreface to the First Edition ix Preface to the Second Edition xiPART I INTRODUCTION1 1What’s in This Book?32What Is Aluminum?52.1Metal in Construction52.2Many Metals from Which to Choose72.3When to Choose Aluminum82.3.1Introduction82.3.2Factors to Consider112.4Aluminum Alloys and Tempers132.4.1Introduction132.4.2Wrought Alloys132.4.3Tempers172.5Structural Applications of Aluminum232.5.1Background232.5.2Building and ConstructionApplications243Working with Aluminum313.1Product Forms313.1.1Extrusions313.1.2Sheet and Plate563.1.3Forgings673.1.4Castings693.1.5Prefabricated Products74iiiiv CONTENTS3.2Coatings and Finishes863.2.1Mill Finish873.2.2Anodized Finishes873.2.3Painted Finishes913.2.4Mechanical Finishes933.2.5Cladding933.2.6Roofing and Siding Finishes943.3Erection94PART II STRUCTURAL BEHA VIOR OF ALUMINUM97 4Material Properties for Design994.1Minimum and Typical Properties994.2Strengths1004.3Modulus of Elasticity(E),Shear Modulus(G),andPoisson’s Ratio(␯)1014.4Fracture Properties1034.5The Effect of Welding on MechanicalProperties1054.6The Effect of Temperature on AluminumProperties1064.7Fire Resistance1084.8Hardness1094.9Physical Properties1094.10Aluminum Material Specifications1104.11Alloy Identification1134.12Certification Documentation1135Explanation of the Aluminum Specification1155.1Tension Members1155.1.1Tensile Strength1165.1.2Net Area1225.1.3Effective Net Area1245.1.4Maximum Slenderness Ratios for TensionMembers1255.2Compression Members1265.2.1Overall Buckling(Columns)1295.2.2Local Buckling(Components ofColumns)1455.3Members in Bending1715.3.1Bending Yielding and Fracture172CONTENTS v5.3.2Bending Buckling1755.3.3Bending Shear1995.4Torsion2045.4.1St.Venant Torsion2065.4.2Warping Torsion2085.4.3A Final Note2105.5Combined Stresses2105.5.1Combined Axial Compression andBending2105.5.2Combined Tension and Bending2135.5.3Combined Shear,Compression,andBending2135.5.4Biaxial and Triaxial Stresses2146Orientation to the Aluminum Specification2176.1Background2176.2The Aluminum Design Manual2196.3Types of Structures Addressed by the AluminumSpecification2236.4Significant Figures and the AluminumSpecification224PART III DESIGN CHECKS FOR STRUCTURALCOMPONENTS2277Structural Members2297.1Tension Member Design Procedure2297.1.1Net Effective Area2307.1.2Allowable Stress2307.1.3Tensile Capacity2317.2Compression Member Design Procedure2317.2.1Overall Column Slenderness Ratio2327.2.2Slenderness Ratio of Cross-SectionalElements2337.2.3Allowable Column Stress of TypicalShapes2337.2.4Summary of Allowable ColumnStress2397.3Bending Member Design Procedure2397.3.1Bending Tension2417.3.2Bending Compression241vi CONTENTS7.3.3Shear2477.4Combined Stresses Design Procedure2477.4.1Combined Axial Compression andBending2477.4.2Combined Tension and Bending2487.4.3Combined Shear,Compression,andBending2498Connections2518.1Mechanical Connections2518.1.1Introduction2518.1.2Types of Fasteners2538.1.3Fastener Material Selection2598.1.4Fastener Mechanical Properties2618.1.5Types of Loads on Fasteners2648.1.6Types of Bolted Connections2658.1.7Holes2678.1.8Failure Modes for Mechanically FastenedJoints2688.1.9Tensile Loads on Fasteners2708.1.10Shear Loads on Fasteners2728.1.11Combined Shear and Tension onBolts2768.1.12Bearing Strength and Edge Distance2778.1.13Tension Strength of Connected Parts2788.1.14Shear Rupture2788.1.15Minimum Spacing and EdgeDistance2818.1.16Maximum Edge Distance andSpacing2818.1.17Screw Connections2848.1.18Minimum Requirements forConnections2888.2Welded Connections2898.2.1Aluminum Welding Processes2898.2.2Selecting a Filler Alloy2918.2.3Types of Welds2928.2.4Comparing Aluminum and Steel FilletWeld Safety Factors3008.2.5Weld Fabrication3008.2.6Weld Quality Assurance304CONTENTS vii9Special Topics3079.1Welded Members3079.1.1What Welding Does to Aluminum3079.1.2Types of Welded Members3109.1.3Welded Tension Members3119.1.4Welded Compression Members3159.1.5Post-Weld Heat Treatment3189.2Fatigue3199.2.1Fatigue—What Is It Again?3209.2.2Fatigue Design:The Ground Rules3229.2.3Variable Amplitude Fatigue Design3269.2.4Aluminum Versus Steel in Fatigue3279.2.5Other Factors in Fatigue3289.2.6A Final Word3299.3Recent Developments in Aluminum Structures3299.3.1Friction Stir Welding3299.3.2Alloy60823309.3.3Aluminum-Lithium Alloys3309.3.4The New Aluminum AutomotiveAlloys3329.3.5Aluminum Metal Matrix Composites333 PART IV DESIGN OF STRUCTURAL SYSTEMS33510Structural Systems Built with Aluminum33710.1Cold-Formed Aluminum Construction33710.1.1Building Sheathing33710.1.2Cold-Formed Aluminum Design34310.1.3Elastically Supported Flanges35010.2Aluminum Frames35110.2.1System Description35110.2.2Model for Analysis35310.2.3Getting Started35410.2.4Analyzing the Dome35810.2.5Design Checks36210.3Aluminum Composite Members37310.3.1Composite Beams37410.3.2Thermal Stresses37510.3.3Dissimilar Material Contact37810.4Aluminum Pressure Piping379viii CONTENTS10.5Aluminum Plate Structures38310.5.1Stiffeners38310.5.2Compressive Strengths38510.5.3Fabrication386PART V LOAD AND RESISTANCE FACTOR DESIGN387 11Load and Resistance Factor Design38911.1New Tricks for Old Dogs38911.2LRFD—The Concept39011.3What’s New:Load Factors39111.4What’s the Same39211.5When Do I Use LRFD?39311.6Which Way Lets Me Use Less Metal?39411.7The General Expression for Comparing LRFD toASD39711.8How They Came Up with the LRFDSpecification39911.9How Do I Actually Start Using LRFD?40511.10The Future of the ASD and LRFD AluminumSpecifications406AppendixesA.Pre-1954Wrought Alloy Designations407B.Section Properties of Common Aluminum Shapes409C.Minimum Mechanical Properties of Aluminum Alloys413D.Allowable Stresses for Elements of Common AluminumShapes425E.LRFD Design Stresses for Elements of Common AluminumShapes429F.Column Buckling Allowable Stress433G.Summary of the Aluminum Specification Design Provisionsfor Columns and Beams435H.Cross Reference to the Aluminum Specification437I.LRFD Design Stresses for Various Alloys441J.Other Aluminum Structural Design Specifications463K.Buckling Constants469L.Metric Conversions475M.Statistics477N.Technical Organizations495Glossary503 References519 Index527PREFACE TO THEFIRST EDITIONThe purpose of this book is to enlighten humanity and contribute to the gen-eral betterment of this orb that we call home.Failing that,we will settle for giving engineers enough guidance in the use of aluminum that they will feel confident designing with it.The Aluminum Association,an industry associ-ation of aluminum producers,publishes the Specifications for Aluminum Structures(hereafter called the Aluminum Specifications),which are the gen-erally accepted criteria for the design of aluminum structures.Our book is keyed to the sixth edition of the Aluminum Specifications,and readers should have access to it.Structural engineering may be regarded as the practice of analyzing and designing structures.The analysis process resolves the loads applied to the structure into the resulting forces and moments in the components of the structure.Structural design is,then,the sizing of the structure’s components to safely sustain these forces and moments.Academic curricula typically train students in structural analysis,as well as in the design methods appropriate to common materials of construction(i.e.,steel,concrete,and perhaps timber), and many excellent texts on these subjects are available.We assume that the reader is already well versed in structural analysis and acquainted with steel design.Our objective is to expand readers’design capability beyond steel, and to present aluminum as another material of construction.While this text is keyed to the Aluminum Specifications,it is also organized to parallel steel design practice.We compare the requirements of the Alu-minum Specifications to the provisions for the design of steel structures found in the American Institute of Steel Construction(AISC)Manual of Steel Con-struction.Those design requirements and considerations that are particular to aluminum,then,are presented in the context of the steel design background that we assume on the part of the reader.In addition to bridging the gap between the familiar old state of steel and the exciting new realm of aluminum,we also seek to bridge the gap between the theoretical and the real worlds.We recognize that one of the greatest difficulties in the transition from student to practitioner is knowing how toixx PREFACEapply the design methods in‘‘the book’’to real-life problems.Whether that book is a text or an industry specification,it often seems that the problem at hand does not neatlyfit into any of the categories given.We include a step-by-step design process for real-world applications.If our steps do not spare readers from a12-step program,then their problems are beyond the scope of this text.J.R ANDOLPH K ISSELLR OBERT L.F ERRY The TGB PartnershipHillsborough,North CarolinaPREFACE TO THESECOND EDITIONWe were frankly surprised by the reaction to thefirst edition of this book. While it never threatened to reach the New York Times best seller list,the favorable comments were more numerous and heartfelt than we had expected. When a reader wrote that‘‘you will be pleased to know that your book is rapidly becoming dog-eared as it is one of the most popular books in our library,’’we knew we had achieved our goal.What may have been the most surprising was the international notice the book received,including a Japanese translation and very favorable European reviews.All this almost made up for the work it took to write it.Once we’d milked the acclaim for all we could,it was time to think about a second edition.The Aluminum Association forced our hand when it revised the Specification for Aluminum Structures in the2000edition of the Aluminum Design Manual.Since this book is a guide to the Specification,an update was due.The changes to the Specification are more than cosmetic,such as chang-ing the title to the singular‘‘Specification.’’They include changes to tension limit states,design compressive strengths for yielding,design bearing stresses, slip-critical connections,screw pull-out strengths,and others,as well as met-rication of mechanical properties.We’ve revised our text accordingly and metricated it,too,although we haven’t been pedantic about metrication in order to preserve readability.We’ve also added the benefit of what is,we hope,additional wisdom gained from experience since thefirst edition.Since the Specification continues to be a living document,we’re dealing with a moving target,but that keeps life interesting.We welcome readers’comments—this time with slightly less trepidation than before.It’s also easier now since this time we have an e-mail address: tgb@.Thanks for your interest in aluminum and our book.J.R ANDOLPH K ISSELLR OBERT L.F ERRY The TGB PartnershipHillsborough,North CarolinaxiPART I Introductiontures pictured in Figure2.3.(Courtesy of Conservatek Industries,Inc.)1What’s in This Book?Our book is about the use of aluminum as a material of construction for structural components.Our major themes are:•The suitability of aluminum as a structural material,•How to design aluminum structural components in accordance with the Aluminum Association’s Specification for Aluminum Structures,•How to apply the design methods to actual structures.We begin by introducing you to aluminum,and we hope that by the end of Part I you are sufficiently well acquainted to be ready to get serious about the relationship.In Part II we explain the design requirements of the2000 edition of the Specification for Aluminum Structures(hereafter called the Alu-minum Specification),published by the Aluminum Association in its Alumi-num Design Manual(4).Those of you who can’t wait to plug and chug may want to jump right ahead to Part III,and refer back to Part II only when you want to know‘‘Where did that come from?’’We assume that you have already had ample exposure to methods of load determination and structural analysis,so we do not replow that ground.We do,however,include in Part II a discussion on local buckling since this is a limit state(i.e.,failure mode to you old-timers)that you may have been sheltered from if your design experience has been primarily with hot-rolled steel.As we discussed in the Preface,we have keyed the discussion of design requirements to the Aluminum Specification.In Part II we compare these design provisions to the more familiar requirements for steel buildings pub-lished by the American Institute of Steel Construction(AISC)in the Speci-fication for Structural Steel Buildings(hereafter called the Steel Specification) (38,39).The Aluminum Specification is primarily intended for building struc-tures;thus,we focus on these applications.Throughout the book we give attention to those features of aluminum that differentiate it from other structural materials,particularly steel.Perhaps the most significant feature that distinguishes aluminum from steel is its extrud-ability.Extruding is the process of forming a product by pushing it through an opening called a die.The cross section of the resulting product is deter-mined by the shape of the die.You may simply prepare a drawing of the34WHAT’S IN THIS BOOK?cross section that you desire for a certain application,then have the mill make a die for producing that shape.This is not the case for steel.We know from personal experience that while custom extrusions enable designers to exercise a great deal of creativity,the process of sizing a unique shape can be very tedious.When designing with steel,engineers often restrict their choices to those shapes listed in tables of compact sections,where the section properties and dimensions are all provided,and the slenderness of the cross-sectional elements have already been checked to confirm that they are not governed by local buckling.While this approach may be safe,it is not very creative.When we create our own shape,however,we assume respon-sibility for determining its section properties and checking the slenderness of the cross-sectional elements.Furthermore,we mayfind that our new section is not compact,and we must then determine the local buckling stress limits. As mentioned previously,Part II includes a comprehensive explanation of the behavior of these slender(light gauge)shapes,which is also pertinent to the design of cold-formed steel structures.Although your task does become more complicated when you venture beyond using off-the-shelf shapes,we will guide you through it.Yourfirst reaction may be that the chore of performing these additional calculations poses too large a cost to pay for obtaining your creative license. We have made it easier,however,by presenting in Part III a straightforward method of performing the design checks required by the Aluminum Specifi-cation.We also provide some simple tables to make the process easier.Thus, if you pay attention,you can achieve maximum design freedom with minimal computational burden.We presented the design checks required for individual structural compo-nents in Part III,and in Part IV we illustrate the application of these design requirements to actual structures.These include an example of cold-formed construction to demonstrate design with slender shapes,and we demonstrate the checks for beams,columns,and combined stresses in the design of a triangulated dome frame.We present the design requirements and examples in the Allowable Stress Design(ASD)format because it is still the method in widest use.In Part V, however,we remove the shroud of mystery from Load and Resistance Factor Design(LRFD),so that when you do encounter it,you need not fear it.Finally,we have compiled useful data in the Appendices,including a cross-reference in Appendix H of the provisions of the Aluminum Specification indexed to where they are discussed in this book.There is also a glossary of technical terms.2What Is Aluminum?This chapter does not deal with the origins of aluminum or how it is refined from bauxite,although the ruins at Les Baux de Provence in southern France are certainly worth a visit.There is an ingot of aluminum in the museum at La Citadelle des Baux as a tribute to the metal that is produced from the nearby red rock,which the geologist Berthier dubbed‘‘bauxite’’in honor of this ancient fortress in1821(135).The ruins of the medieval stronghold, though,are the real attraction.We’ll defer to Fodor’s and Frommer’s on the travel tips,and to Sharp on a discussion of the history,mining,and production of aluminum(133).Our purpose in this chapter is to discuss aluminum’s place in the families of structural metals.2.1METAL IN CONSTRUCTIONWe include aluminum with steel and reinforced concrete as a metal-based material of construction.While our basis for this grouping may not be im-mediately obvious,it becomes more apparent when considered in an historical context(103).Prior to the development of commercially viable methods of producing iron,almost all construction consisted of gravity structures.From the pyra-mids of the pharoahs to the neoclassical architecture of Napoleonic Europe, builders stacked stones in such a way that the dead load of the stone pile maintained a compressive state of force on each component of the structure (see Figure2.1).The development of methods to mass-produce iron,in ad-dition to spawning the Industrial Revolution in the nineteenth century,resulted in iron becoming commercially available as a material of construction.Ar-chitecture was then freed from the limitations of the stone pile by structural components that could be utilized in tension as well as compression.Amer-ican architect Frank Lloyd Wright observed that with the availability of iron as a construction material,‘‘the architect is no longer hampered by the stone beam of the Greeks or the stone arch of the Romans.’’Early applications of this new design freedom were the great iron and glass railway stations of the Victorian era.Builders have been pursuing improvements to the iron beam ever since.An inherent drawback to building with iron as compared to the old stone pile is the propensity of iron to deteriorate by oxidation.Much of the effort to improve the iron beam has focused on this problem.One response has56WHAT IS ALUMINUM?Figure2.1Pont du Gard in southern France.An aqueduct that the ancient Romans built by skillfully stacking stones.2.2MANY METALS FROM WHICH TO CHOOSE7 been to cover iron structures with a protective coating.The term coating may be taken as a reference to paint,but it is really much broader than that.What is reinforced concrete,for example,but steel with a very thick and brittle coating?Because concrete is brittle,it tends to crack and expose the steel reinforcing bars to corrosion.One of the functions served by prestressing or posttensioning is to apply a compressive force to the concrete in order to keep these cracks from opening.While one approach has been to apply coatings to prevent metal from rusting,another has been to develop metals that inherently don’t rust.Rust may be roughly defined as that dull reddish-brown stuff that shiny steel be-comes as it oxidizes.Thus,the designation of‘‘stainless’’to those iron-based metals that have sufficient chromium content to prohibit rusting of the base metal in atmospheric service.The‘‘stain’’that is presented is the rust stain. Stainless steel must have been a term that originated in someone’s marketing department.The term confers a quality of having all the positive attributes of steel but none of the drawbacks.If we were to apply a similar marketing strategy to aluminum,we might call it‘‘light stainless steel.’’After all,it prevents the rust stain as surely as stainless steel does,and it weighs only about one-third as much.Engineers who regard aluminum as an alien material may be more favorably disposed toward‘‘light stainless steel.’’For the past century and a half,then,structural engineers have relied on metals to impart tension-carrying capability to structural components.Tech-nical development during that time has included improvement in the prop-erties of the metals available for construction.One of the tasks of designers is to determine which metal best suits a given application.2.2MANY METALS FROM WHICH TO CHOOSEStructural metals are often referred to in the singular sense,such as‘‘steel,’’‘‘stainless steel,’’or‘‘aluminum,’’but,in fact,each of these labels applies to a family of metals.The label indicates the primary alloying element,and individual alloys are then defined by the amounts of other elements contained, such as carbon,nickel,chromium,and manganese.The properties of an alloy are determined by the proportions of these alloying elements,just as the characteristics of a dessert are dependent on the relative amounts of each ingredient in the recipe.For example,when you mix pumpkin,spices,sugar, salt,eggs,and milk in the proper quantities,you make a pumpkin piefilling. By addingflour and adjusting the proportions,you can make pumpkin bread. Substituting shortening for the pumpkin and molasses for the milk yields ginger cookies.Each adjustment of the recipe results in a different dessert. Whereas the addition offlour can turn piefilling into bread,adding enough chromium to steel makes it stainless steel.8WHAT IS ALUMINUM?While this is a somewhat facetious illustration,our point is that just as the term dessert refers to a group of individual mixtures,so does the term steel. Steel designates a family of iron-based alloys.When the chromium content of an iron-based alloy is above10.5%,it is dubbed stainless steel(136).Even within the stainless steel family,dozens of recognized alloys exist,each with different combinations of alloying ingredients.Type405stainless steel,for example,contains11.5%to14.5%chromium and1.0%or less of several other elements,including carbon,manganese,silicon,and aluminum.Should the alchemist modify the mixture,such as by switching the relative amounts of iron and aluminum,substituting copper for carbon and magnesium for manganese,and then leaving out the chromium,the alloy might match the composition of aluminum alloy2618.As this four-digit label implies,it is but one of many aluminum alloys.Just as with desserts,there is no one best metal mixture,but rather different mixtures are appropriate for different oc-casions.The intent of this text is to add aluminum-based recipes to the rep-ertoire of structural engineers who already know how to cook with steel. 2.3WHEN TO CHOOSE ALUMINUM2.3.1IntroductionToday aluminum suffers from a malady similar to that which afflicted toma-toes in the eighteenth century:many people fail to consider it out of super-stition and ignorance.Whereas Europeans shunned tomatoes for fear that they were poisonous,engineers seem to avoid aluminum for equally unfounded reasons today.One myth is that aluminum is not sufficiently strong to serve as a structural metal.The fact is that the most common aluminum structural alloy,6061-T6, has a minimum yield strength of35ksi[240MPa],which is almost equal to that of A36steel.This strength,coupled with its light weight(about one-third that of steel),makes aluminum particularly advantageous for structural ap-plications where dead load is a concern.Its high strength-to-weight ratio has favored the use of aluminum in such diverse applications as bridge rehabili-tation(Figure2.2),large clear-span dome roofs(Figure2.3),andfire truck booms.In each case,the reduced dead load,as compared to conventional materials,allows a higher live or service load.Aluminum is inherently corrosion-resistant.Carbon steel,on the other hand,has a tendency to self-destruct over time by virtue of the continual conversion of the base metal to iron oxide,commonly known as rust.Al-though iron has given oxidation a bad name,not all metal oxides lead to progressive deterioration.Stainless steel,as noted previously,acquires its fea-ture of being rust-resistant by the addition of chromium to the alloy mixture. The chromium oxidizes on the surface of the metal,forming a thin transparent film.This chromium oxidefilm is passive and stable,and it seals the base2.3WHEN TO CHOOSE ALUMINUM9Figure2.2Installation of an aluminum deck on aluminum beams for the Smithfield Street Bridge in Pittsburgh,Pennsylvania.(Courtesy of Alcoa)metal from exposure to the atmosphere,thereby precluding further oxidation. Should thisfilm be scraped away or otherwise damaged,it is self-healing in that the chromium exposed by the damage will oxidize to form a newfilm (136).Aluminum alloys are also rendered corrosion-resistant by the formation of a protective oxidefilm,but in the case of aluminum it is the oxide of the base metal itself that has this characteristic.A transparent layer of aluminum oxide forms on the surface of aluminum almost immediately upon exposure to the atmosphere.The discussion on coatings in Section3.2describes how color can be introduced to this oxidefilm by the anodizing process,which can also be used to develop a thicker protective layer than one that would occur naturally.Corrosion-prone materials are particularly problematic when used in ap-plications where it is difficult or impossible to maintain their protective coat-ing.The contacting faces of a bolted connection or the bars embedded in reinforced concrete are examples of steel that,once placed in a structure,are not accessible for future inspection or maintenance.Inaccessibility,in addition to preventing repair of the coating,may also prevent detection of coating10WHAT IS ALUMINUM?Figure2.3Aerial view of a pair of aluminum space frames covered with millfinish (uncoated)aluminum sheeting.(Courtesy of Conservatek Industries,Inc.) failure.Such locations as the seam of a bolted connection or a crack in concrete tend to be places where moisture or other agents of corrosion collect.Furthermore,aluminum is often used without anyfinish coating or paint-ing.The cost of the initial painting alone may result in steel being more expensive than aluminum,depending on the quality of coating that is speci-fied.Coatings also have to be maintained and periodically replaced.In ad-dition to the direct cost of painting,increasing environmental and worker-2.3WHEN TO CHOOSE ALUMINUM11 safety concerns are associated with painting and paint preparation practices. The costs of maintaining steel,then,give aluminum a further advantage in life-cycle cost.2.3.2Factors to ConsiderClearly,structural performance is a major factor in the selection of structural materials.Properties that affect the performance of certain types of structural members are summarized in Table2.1.For example,the strength of a stocky compression member is a function of the yield strength of the metal,while the strength of a slender compression member depends on the modulus of elasticity.Since the yield strength of aluminum alloys is frequently comparable to those of common carbon and stainless steels,aluminum is very competitive with these materials when the application is for a stocky column.Conversely,since aluminum’s modulus of elasticity is about one-third that of steel’s,aluminum is less likely to be com-petitive for slender columns.Strength is not the only factor,however.An example is corrosion resis-tance,as we noted above.Additional factors,such as ease of fabrication (extrudability and weldability),stiffness(modulus of elasticity),ductility (elongation),weight(density),fatigue strength,and cost are compared for three common alloys of aluminum,carbon steel,and stainless steel in Table 2.2.While cost is critical,comparisons based on cost per unit weight or unit volume are misleading because of the different strengths,densities,and other properties of the materials.Averaged over all types of structures,aluminum components usually weigh about one-half that of carbon steel or stainless steel members.Given this and assigning carbon steel a relative cost index of 1results in an aluminum cost index of2.0and stainless cost index of4.7.If initial cost were the only consideration and carbon steel could be used without coatings,only carbon steel would be used.But,of course,other factors come TABLE2.1Properties That Affect Structural Performance of Metals Structural Performance of Propertytensile members yield strength,ultimate strength,notchsensitivitycolumns(compression members)yield strength,modulus of elasticity beams(bending members)yield strength,ultimate strength,modu-lus of elasticityfasteners ultimate strengthwelded connections ultimate strength offiller alloy;ultimatestrength of heat-affected base metal。

ferrous alloys铁合金More than 90% by weight of the metallic materials used by human beings are ferrous alloy. This represents an immense family of engineering materials with a wide range of microstructures and related properties. The majority of engineering designs that require structural load support or power transmission involve ferrous alloys. As a practical matter, those alloys fall into two broad categories based on the carbon in the alloy composition. Steel generally contains between wc=0.05% and wc=4.5%.超过90%的重量的金属材料使用的人类是铁合金。

这是一个巨大的工程材料的家庭与广泛的微观结构和相关的属性。

大部分的工程设计,需要结构性的负载支持或电力传输涉及铁合金。

作为一个实际问题,这些合金分为两大类基于碳在合金成分。

钢一般包含在wc = 0.05%和wc = 4.5%。

Within the steel category,we shall other than carbon is used.A compositon of 5% total noncarbon high alloy steels. Those alloy additions are chosen carefully becouse they invariably bring with them sharply increased material costs. They are justified only by essential improvements in improvements such as higher strength or improved corrosion resistance在钢的类别,我们将使用碳。

PROCESS FOR THE EXTENSION OF THE EFFECTIVE SURFACE OF ALUMINIUM ELECTRODES OR FOILS FORELECTROLYTIC CAPACITORSAbstract of GB11692341,169,234. Electrolytic etching of aluminium. H-W. PAEHR. Jan. 16, 1967 [Jan.21, 1966], No. 2198/67. Heading C7B. In a process for the extension of the effective surface area of aluminium electrodes or aluminium foil for electrolytic capacitors by anodic corrosion in a bath containing an electrolyte and a counter- electrode, there is applied across the electrode or foil to be corroded and the counter-electrode a direct voltage and superimposed periodic voltage pulses, e.g. at a frequency of 10-100 cycles/sec, which interrupt the substantially constant corrosion current due to said direct voltage and have a half- width of less than 10% of the pulse repetition period. The pulsating voltage may be provided by supplying negative voltage pulses to the part to be corroded and/or positive voltage pulses to the counter- electrode. Pulse shapes which may be used (see Fig.2, not shown) include rectangular and trapezoid pulses, and the pulses are preferably of such height that the voltage difference between the electrodes is equal to the polarization of aluminium with re- spect to the electrolyte. An aqueous solution of sodium chloride may be used as electrolyte.Description of GB1169234PATENTSPECIFICATIONDRAWINGS ATTACHED 1, 1695234 Date of Application and filing Complete Specification: 16 Jan., 1967.No. 2198/67.Application made in Germany (No. P38594 VlIc/2Jg) on 21 Jan., 1966. Complete Specification Published: 29 Oct., 1969.Index at acceptance: -C7 B(31, 17) International Classification:-C 23 b 3102COMPLETE SPECIFICATIONProcess for the Extension of the Effective Surface of Aluminium Electrodes or Foils for Electrolytic Capacitors I, HANS-WERNER PAEHR, of 20 Niddastrasse, 638 Bad Homburg, Germany, of German nationality, do herebv declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: -The present invention relates to a process for the anodic corrosion of aluminium electrodes or aluminium foils for electrolytic capacitors by means of a pulse-superimposed direct current, to extend their effective surface areas.Processes of this type as described in Canadian Patent Specification 582328, wherein a unipolar current pulsing above a minimum value is used. With these processes, therefore, current pulses of the same polarity are superirposed on direct currents. Tests with these processes have shown that the pulse rate has to be regarded as being only one of a number of parameters which are decisive for corrosion, such as current density, electrolyte concentration and electrolyte temperature, and that, by means of a unipolar current pulsing above a minimum value, corrosion qualities will only be obtained which, by suitable selection of the other parameters, may even be obtained by means of unpulsed direct current. In addition, alternating current processes have also been tested, in which the current in the corrosion bath is periodically reversed. With the latter processes smaller capacitance yields have been obtained than with direct current.The present invention resides in a process for the extension of the effective surface area of aluminium electrodes or aluminium foils for electrolvr:z capacitors by anodic corrosion in a bath containing an electrolyte and a counterelectrode, in which there is applied across the electrode or foil to be corroded and the counter-electrode a direct voltage and superimposed voltage pulses periodically interrupting said corrosion, which voltage pulses interrupt a substantially constant corrosion current due to said direct voltage and have a half-width of less than 10% of the pulse repetition period.Negative pulses may be applied to the electrode to be corroded and/or positive pulses to the counter-electrode. This corrosion method will not be influenced by the undulation or ripple of the anodic corrosion voltage.It will, therefore, not be necessary to screen the curent supplied by commercial rotary current rectifiers.The invention will be further described with reference to the accompanyingdrawings, in which:Figures la and lb are circuit diagrams of apparatus for anodic corrosion of aluminium electrodes or foils; Figure 2 is a curve showing the variation of the voltage U across the corrosion bath with time t; Figure 3 shows the variation of the capacitance C of a corroded electrode with negative pulse amplitude AP; and Figure 4 is an enlarged sectional view of a foil corroded by my process.Figures la and lb show a corrosion bath B containing the electrode A to be corroded as anode and counter-electrodes or cathodes K, a pulse source P and a direct current source G being connected in series in Figure la, and in parallel in Figure lb. The source G has its positive pole connected to the electrode A and its negative pole to the cathode K so as to pass a substantially constant corrosion cur1,169,234 rent between the electrode A and cathode K.Source P is arranged to apply negative-going pulses to electrode A to interrupt the corrosion curent. In Figure la, a choke D1 and a capacitor Cl bridge the pulse source P and the direct current source G respectively so that both current sources will be fully effective with respect to the corrosion bath B. In Figure lb, a capacitor C2 and a choke D2 ensure that the sources P and G will not shortcircuit each other. If the internal impedances of P and G have corresponding properties, the elements Cl or C2 and D1 or D2 may be omitted. In particular with commercial large scale plants, the inductivities of the feed lines to the current source G are frequently so great that the choke D2 in Figure lb will not be required. If the pulse source P in Figure lb is provided with transistors, C2 may be omitted, and the direct current source G may serve as supply source for the transistors. The pulse source should have a high internal resistance Ri which, with the inductivity Ls of the supply lines which canLs not be avoided, will form a time constant Ri as small as possible so that the pulses will arrive at the corosion bath without any attenuation or distortion.Further details of the arrangements will not be discussed, it will merely be observed that any suitable known direct current and pulse sources may be used if they are of suflicient capacity.As shown in Figure 2, the total voltage U across the corrosion bath consists of a direct voltage G and a pulse voltage P1, P2, P3, P4 or P5 which has a repetition period tl and a pulse length Electrolyte: aqueous chloride Temperature: 700 C.Corrosion time: 130 secs.Direct current density: 0.6 A/acn Direct voltage: 5.2 volts Pulse shape: rectangular Pulse frequency: 40 cycles/ Pulse width: approx. 1 Pulse height:variable be AP: variable be In Figure 3 the capacitance C of 1 cm' of foil has been shown in relation to &P. CQ is the capacity obtained with direct current corrosion under otherwise identical conditions.Maximum capacitance C, in this case, is obtained at AP= -1.2 volts, amounting to 1.55 times the direct current value Co. But, even at AP values of -1.7 and -0.4 volts, an increase in capacity of 30% is achieved by pulsation. Even at positive AP values (i.e. pulse amplitude less than G) the improvement obbased upon the half width value t2. The amplitude of the pulses is preferably greater than the direct voltage so that during the pulse maximum a negative pulse of amplitude AP, preferably 0.8-1.8 vots is applied across the bath. F'e 2 shows various types of pulses suitable for the process according to the present invention. However, rectangular pulses such as P1 or trapezoid pulses such as P2 are most suitable, especially so if they have steep flanks the respective rise and fall times of each of which are smaller than 15% of the pulse duration.In tests, pulse frequencies from 10 to 100 cycles per second have been used, i.e. pulse periods amounted to 10 to 100 msecs. In all cases a pulse duration which was smaller than 10% of the pulse period was employed. The d.c. corrosion voltage was between 5 and 10 volts. Under these circumstances an optimum effect has been obtained in any case if the pulses were of such height that the voltage at the electrode to be corroded, as compared to the voltage at the counter-electrode during the pulse maximum, was more negative by an amount corresponding to 8 to 33 % of the d.c.corrosion voltage, and if the corrosion current during this time was zero or slightly negative. Optimum dimensioning of the pulse frequency, pulse duration and pulse height depends, apart from pulse shape, upon many factors, especially upon resistance and inductivity of the foil, the corosion bath and the supply lines. Following is a practical example: In a standing bath a series of 0.1 mmn thick high purity (99.99%) aluminium foils was corroded and subsequently formed at 400 volts in the following conditions:solution containing 3% sodium r rsecond etween 4.6 and 7.6 volts etween +0.6 and -2.4 volts.tainable still amounts to 10-20%. At AP= 100 -2 volts capacity considerably decreases, obviously due to the fact that increasing current reversal occurs which drives sodium ions into the corroded pores.Corroded foils obtained in the process according to the present invention have extremely high capacitance yields and a high porosity. Eeven the structure of the channels corroded into the foil is remarkable: the width of these channels is small as cumpared 110 1,169,234 to their depth. It will therefore be possible, without effecting complete destruction of the foil, to obtain a far more intensedepth corrosion than with the corrosion processes which are already known, in which deepening of the corrosion channels has always been connected with widening of the same. Figure 4 is a 1: 300 enlarged sectional view of a foil produced according to the present invention, the regions which have been corroded away being stippled. The apparently separate portions of the remaining foil were interconnected in front of or behind the section plane.On the reaction in the corrosion bath the following ideas have been developed which are suitable as a working hypothesis but which may not be absolutely true.During the corrosion process the foil is, due to the pulses, periodically depolarized for a short period of time so that gas bubbles which are maintained in the corrosion pores under high electrostatic pressure will escape and at the same time expel from the pores the electrolyte and the decomposition products arising during corrosion. The decrease in voltage effected by the pulse must be a sudden one so that expansion of the gases occurs explosively, and the pulse duration must be short so that the electrolyte when reentering the corrosion channels is already again under the effect of the corrosion voltage. Obviously, this is a pump effect which periodically drives fresh electrolyte into the corrosion channels.A further effect of the pulses is that the foil is capacitively discharged by them. In the following this will be discussed in detail.The depth effect with anodic direct current corrosion results from the fact that in those areas which are not attacked by the electrolyte hydroxide layers will be established the surfaces of which are capacitatively charged so that the corrosion ions are deflected from these areas and routed towards the corrosion channels already existing. This effect, however, has the result that, with direct current corrosion, after a certain period of time new corrosion pores will re longer occur and the old ones will only be further opened. Chargedhydroxide layers may even occur in the corrosion process according to the present invention, but they will periodically be discharged by the pulses so that between pulses corrosion ions may arrive at the layers and decompose them.In this way, an increase in the number of corrosion channels results.The size of AP required for obtaining a high degree of roughening, i.e. of the negative surplus of the pulses with respect to the direct current, can also be theoretically explained:Since it is necessary to completely cut off the corrosion current during thepulse duratioi;, the tendency of aluminium to be decomposed in the electrolyte without exterior voltage, must be compensated. For this enctd AP is made equal to the polarisation voltage of aluminium with respect to the electrolyte. The present invention does not only relate to the examples, arrangements and rates shown, but it refers to any and all methods and equipment which are based upon the principal idea of interrupting periodically and for a short period of time a corrosion process for obtaining electrodes having a high degree of roughening as well as a high porosity.Claims of GB1169234WHAT I CLAIM IS: -1. A process for the extension of the effective surface area of aluminium electrodes or aluminium foils for electrolytic capacitors by 80 anodic corrosion in a bath containing an electrolyte and a counter-electrode, in which there is applied across the electrode or foil to be corroded and the counter-electrode a direct voltage and superimposed voltage pulses 85 periodically interrupting said corrosion, which voltage pulses interrupt a substantially constant corrosion current due to said direct voltage and have a half-width of less than 10%',, of the pulse repetition period. 902. A process according to claim 1, in which negative voltage pulses are supplied to the foil or electrode to be corroded and/or positive voltage pulses to the counter-electrode.3. A process according to claim 1 or 2 95 in which rectangular pulses or trapezoid pulses are used the rise and fall times of which are respectively, in each case, less than 15%' of the pulse duration.4. A process according to claim 1, 2 or 3 100 in which the pulse frequency ranges within 10 and 100 cycles/second.5. A process according to claim 1, 2 or 3 in which the pulse frequency is 40 cycles/ second and the pulse duration is about 1 msec. 1056. A process according to any of claims 1 to 5 in which the pulses are of such height that the voltage at the electrode to be corroded during the pulse maximum is more negative by 0.8 to 1.8 volts than the voltage 110 at the counter-electrode.7. A process according to any of claims 1 to 5 in which the pulses are of such height that the voltage differences at pulse maximum between the aluminium electrode to be corroded and the counter-electrode are equal to the polarisation voltage of aluminium with respect to the electrolyte.8. A process according to any of claims 1 to 7 in which corrosion is effected inan 120 aqueous solution containing 3 % sodium chloride at a temperature of 70 C and with a direct curent density, based upon foil surface, of 0.6 A/cm2.9. A process according to claim 1 for 125 corroding aluminium foils or electrodes, substantially as herein described and illustrated in the accompanying drawing.10. An aluminium foil for electrolytic cap1,169,234 acitors produced by a method accordn to any one of the preceding claims, the total thickness of said foil being full of corroded channels and the width of said channels being smaller than their depth.11. Apparatus for corroding aluminium electrodes or foils by the method claimed in any of claims 1 to 9, including a bath for electrolyte, a counter-electrode, and a d.c.source and a pulse source connected in senes or in parallel with each other, the.c source being arranged and adapted to produce a substantially constant corrosion current between the alunminium electrode or foil and the counter-elect, and the pulse source being armge& and adptd to produce pulses interrupting the said current and having a half width less thin 10% of the pulse repetition period.12. Apparatus as claimed in claim 11 in which the pulse source has a high internal resista.MAIKS & CLERK, Cha i Patent Agents, Agents for the Applicant(s).Printed for Her Majesty's Stationery Office by the Courier Press, Leamington Spa, 1969.Published by the Patent Office, 25, Southampton Buildings, London, W.C.2, from which copies may be obtainem。