下载文档原格式
材料测试方法英语以下是一些常见的材料测试方法的英文表达：1. Tensile Testing（拉伸测试）：A method of testing the mechanical properties of materials under tension.2. Hardness Testing（硬度测试）：A method of measuring the resistance of a material to indentation or scratching.3. Impact Testing（冲击测试）：A method of testing the ability of a material to absorb energy during sudden loading.4. Fatigue Testing（疲劳测试）：A method of testing the behavior of materials under repeated cyclic loading.5. Non-destructive Testing（无损检测）：A method of testing materials without causing damage to the test specimen.6. Corrosion Testing（腐蚀测试）：A method of testing the resistance of materials to chemical or electrochemical attack.7. Thermal Testing（热测试）：A method of testing the response of materials to heat or temperature changes.8. Microscopy（显微镜检测）：A method of examining materials at a microscopic level to analyze their structure and properties.9. Spectroscopy（光谱学）：A method of analyzing materials by studying the interaction between matter and electromagnetic radiation.10. X-ray Testing（X射线检测）：A method of testing materials using X-ray radiation to evaluate internal structure and defects.。
第27卷第4期粉末冶金材料科学与工程2022年8月V ol.27 No.4 Materials Science and Engineering of Powder Metallurgy Aug. 2022 DOI:10.19976/ki.43-1448/TF.2022030单级时效处理对2A97铝锂合金组织、力学性能和腐蚀性能的影响游任轩，马运柱，汤娅，赵心阅，刘文胜(中南大学粉末冶金研究院，长沙 410083)摘要：为了确定单级时效制度对2A97铝锂合金组织、力学性能和腐蚀性能的影响，采用室温拉伸、晶间腐蚀、剥落腐蚀、电化学腐蚀和TEM观察等方法，对不同单级时效处理后的合金组织和性能进行表征测试。
结果表明：随着时效温度升高，2A97铝锂合金达到最佳力学性能所需时间缩短。
随时效温度升高、时效时间延长，合金的抗腐蚀性能下降。
165 ℃时效60 h后，合金的抗拉强度、屈服强度和伸长率分别达到549 MPa、484 MPa和8.8%，晶间腐蚀等级为4级，剥落腐蚀评级EC。
关键词：2A97铝锂合金；单级时效；显微组织；力学性能；腐蚀性能中图分类号：TG146.21文献标志码：A 文章编号：1673-0224(2022)04-398-11Effects of single-stage aging treatment on microstructure, mechanical properties and corrosion properties of 2A97 Al-Li alloysYOU Renxuan, MA Yunzhu, TANG Ya, ZHAO Xinyue, LIU Wensheng(Powder Metallurgy Research Institute, Central South University, Changsha 410083, China)Abstract: In order to determine the effects of single-stage aging regime on the microstructures, mechanical properties and corrosion properties of 2A97 Al-Li alloys, the methods of room temperature tensile, intergranular corrosion, exfoliation corrosion, electrochemical corrosion and TEM observation were used to investigate the microstructure, mechanical properties and corrosion properties of 2A97 Al-Li alloys after different single-stage aging treatments. The alloys were tested and characterized. The results show that with increasing the aging temperature, the aging time for 2A97 Al-Li alloys to obtain the best mechanical properties decreases. With increasing the aging temperature and aging time, the corrosion resistance of the alloys decreases. After aging at 165 ℃for 60 h, the tensile strength, yield strength and elongation of the alloys are 549 MPa, 484 MPa, and 8.8%, respectively, the intergranular corrosion is grade 4, and the exfoliation corrosion grade is EC.Keywords: 2A97 Al-Li alloys; single-stage aging; microstructure; mechanical property; corrosion property铝锂合金由于低密度、高比强度、高比刚度和高弹性模量的特点，在航空航天领域有着越来越广泛的应用。
铜在钢中的作用概述作者：卞小龙王永霞杨金业刘鹏鹏来源：《科技创新与应用》2019年第26期摘; 要：文章从含铜钢的力学性能、耐蚀性能和抗菌性能方面论述了铜在钢中的作用，将铜加入钢中并经过适当的热处理后，材料的强度，硬度、伸长率和屈强比会得到改善;铜在钢中能提高基体的整体电位，使得材料的耐腐蚀性能提高;含铜钢中的富铜相具备抗菌杀菌作用。
关键词：含铜钢;时效处理;力学性能;耐蚀性能;抗菌性能中图分类号：TG151.1; ; ; ;文献标志码：A 文章编号：2095-2945（2019）26-0041-02Abstract： Mechanical properties， corrosion resistance and antibacterial properties of copper-bearing steel were discussed in this paper. After adding copper into steel and undergoing proper heat treatment， the strength， hardness， elongation， ratio of yield strength to tensile strength of the material was improved. The overall potential of the matrix was increased， corrosion resistance of the material was improved， and antibacterial properties was given by copper-rich phase.Keywords： copper-bearing steel; aging treatment; mechanical properties; corrosion resistance property; antibacterial property1 概述钢铁材料作为国民经济的基本支柱之一在各个领域都有着极大的应用价值。
W机械工程材料IX)I ： 10.11973/jxgccl202101006焊前和焊后调质处理下25C r 2N i 4M o V 钢焊接接头的组织及性能张敏,仝雄伟，李洁，许帅，贾芳(西安理工大学材料科学与工程学院，西安710048)摘要：对比研究了焊前和焊后调质处理条件下25C r 2N i 4M o V 钢焊接接头的显微组织、力学 性能和耐腐蚀性能，调质处理工艺为920 °CX1 h 油淬+580 °C X 2 h 回火，焊接工艺为手工焊条电 弧焊。
结果表明：焊前调质处理的接头焊缝组织为板条马氏体+S-铁素体+ M 23C S 碳化物，焊后调 质处理使焊缝中的S-铁素体溶解，形成了板条马氏体+回火索氏体+M 23C S 碳化物；焊后调质处理 条件下，焊缝中的板条马氏体细小均匀，M 23C 6碳化物呈颗粒状分布于原奥氏体晶界和马氏体板条 晶界处，焊缝的强度、冲击初性和耐腐蚀性能均优于焊前调质处理的。
关键词：25C r 2N i 4M o V 钢；焊缝；调质；显微组织；力学性能；耐腐蚀性能中图分类号：TG444文献标志码：A文章编号：1000-3738(2021)01-0034-07Microstructure and Properties of 25Cr2Ni4MoV Steel Welded Joint underPre-welding and Post-welding Quenching and Tempering TreatmentZHANG Min, TONG Xiongwei, LI Jie. XU Shuai. JIA Fang(School of Materials Science and Engineering ，Xi’an University of Technology, Xi’an 710048，China)Abstract ： M icrostructure, mechanical properties and corrosion resistance of 25Cr2Ni4M oV steel welded jointwere compared and studied under conditions of pre-welding and post-welding quenching and tem pering treatm ents.T he quenching and tem pering proceSvS was oil quenching at 920 °C for 1 h and tem pering at 580 °C for 2 h. The welding process was manual electrode arc welding. The results show that by pre-welding quenching and tem pering, the m icrostructure of the joint weld zone consisted of lath m artensite» netw ork S-ferrite and M 23C 6 carbide. A fter the post-welding quenching and tem pering，the 5-ferrite in the weld was dissolved, and the lath m artensite, tem pered sorbite and M 23C 6 carbide were formed. U nder the post-welding quenching and tem pering condition, the lath m artensite in the weld was small and uniform , and the M 23C 6 carbide distributed in granular shapes on original austenite grain boundaries and m artensite lath grain boundaries ； the strength, impact toughness and corrosion resistance were better than those by the pre-welding quenching and tem pering treatm ent.Key words ： 25Cr2Ni4M oV steel ； weld zone ； quenching and tem pering ； m icrostructure ； mechanicalproperties ； corrosion resistance25Cr2Ni4M〇V 钢中马氏体的形成，但若奥氏体化温 度过高，得到的板条马氏体较粗大[1]。
8mm的x80管线钢生产工艺流程英文回答：The production process of 8mm x 80 pipeline steel involves several steps to ensure the quality and durability of the final product. Firstly, the raw materials, including iron ore, coal, and limestone, are gathered and processed. The iron ore is heated in a blast furnace to remove impurities and create molten iron. Then, the molten iron is combined with recycled steel and other alloys to create the desired composition for the pipeline steel.After the steel composition is determined, it is then cast into large slabs or billets. These slabs are heated and rolled into thin strips called coils. The coils are then sent through a series of machines to remove any impurities and shape them to the desired dimensions. This process is known as hot rolling and helps to improve the strength and ductility of the steel.Once the coils are shaped, they undergo a process called annealing, where they are heated and cooled to relieve any internal stresses and improve the steel's mechanical properties. This step is crucial in ensuringthat the pipeline steel can withstand the pressures and stresses it will encounter during its use.After annealing, the coils are further processed through a series of machines to clean and coat them with a protective layer. This layer helps to prevent corrosion and extends the lifespan of the pipeline steel. The coatedcoils are then cut into smaller sections and formed into pipes through a process called welding or seamless tube production, depending on the desired specifications.Finally, the pipes are subjected to various tests and inspections to ensure they meet the required standards. These tests include checking the dimensions, mechanical properties, and corrosion resistance of the pipes. Once the pipes pass the tests, they are ready for delivery to the customers.中文回答：8mm x 80管线钢的生产过程涉及多个步骤，以确保最终产品的质量和耐久性。
一种高熵过渡金属二硼化物及其制备方法这种高熵过渡金属二硼化物具有良好的热稳定性和机械性能。
This high-entropy transition metal diboride exhibits excellent thermal stability and mechanical properties.该二硼化物由五种过渡金属元素组成，包括铝、钒、铬、铌和钛。
The diboride is composed of five transition metal elements, including aluminum, vanadium, chromium, niobium,and titanium.制备方法包括混合过渡金属元素和硼源、高温固相反应和后续热处理。
The preparation method involves mixing transition metal elements and a boron source, followed by high-temperaturesolid-phase reaction and subsequent heat treatment.高熵效应导致了该二硼化物具有优异的热稳定性和抗氧化性能。
The high-entropy effect results in the diboride having excellent thermal stability and oxidation resistance.该二硼化物在高温、高压和腐蚀性环境下仍然保持结构稳定。
The diboride maintains structural stability under high temperature, high pressure, and corrosive environments.该二硼化物可用作高温结构材料、涂层材料和陶瓷材料。
The diboride can be used as high-temperature structural materials, coating materials, and ceramic materials.制备过程中需要严格控制反应条件和成分比例，以确保产物的高质量。
锌镁铝镀层金相锌镁铝（Zinc Magnesium Aluminum，ZMA）镀层是一种新型的镀层材料，在金属加工和防腐领域具有广泛的应用。
它由锌、镁和铝组成，通过热浸镀工艺将其镀在基材表面。
锌镁铝镀层具有良好的耐腐蚀性、良好的焊接性能和较高的硬度，因此在汽车、建筑和电子等行业中得到了广泛应用。
本文将讨论锌镁铝镀层的金相结构、镀层性能以及其应用领域。
锌镁铝镀层的金相结构主要由金属相和化合物相组成。
金属相主要是由锌、镁和铝单独存在的晶粒组成，这些晶粒的分布和尺寸决定了镀层的致密度和耐蚀性。
化合物相主要是由锌、镁和铝的化合物组成，如ZnMgAl2O4等，这些化合物在镀层中具有强大的保护性能，能够提高镀层的耐蚀性。
锌镁铝镀层具有优异的性能。
首先，它具有优异的耐腐蚀性能，能够有效地抵抗盐雾、酸碱等腐蚀介质的侵蚀。
研究表明，锌镁铝镀层在盐雾试验中能够达到1000小时以上的防腐蚀寿命。
其次，锌镁铝镀层具有良好的焊接性能，能够在焊接过程中保持镀层的完整性，减少焊接变色和开裂的风险。
最后，锌镁铝镀层还具有较高的硬度，能够提高基材的耐磨性和抗刮伤性。
锌镁铝镀层已经在许多行业得到了广泛的应用。
在汽车行业中，它被用作车身和发动机零部件的防腐镀层，能够有效地抵抗路面盐雪和湿润环境对汽车的侵蚀。
在建筑行业中，锌镁铝镀层被用作钢结构材料的防腐层，能够延长钢结构的使用寿命。
在电子行业中，锌镁铝镀层被用作电子元件的镀层，能够提高电子元件的连接可靠性和耐久性。
综上所述，锌镁铝镀层是一种具有优异性能的镀层材料。
它具有良好的耐腐蚀性、焊接性能和硬度，广泛应用于汽车、建筑和电子等领域。
锌镁铝镀层的金相结构以及其卓越的性能为其在各行业中的应用提供了坚实的基础。
参考文献：1. Deng, X. M., et al. (2014). "Influence of aging treatment on corrosion behavior and interfacial bonding strength of Zn‐Mg‐Al coated on steel sheets." Materials and Corrosion 65(2): 135-146.2. Chen, S., et al. (2016). "Evaluation of the mechanical and corrosion properties of a Zn–Mg–Al coating on low-carbon steel processed by friction stir welding." Journal of Materials Science and Technology 32(9): 841-850.3. Zhang, Z., et al. (2019). "Microstructure and Corrosion of anFe–Al Intermetallic Coating Prepared on the Surface of Zn–Mg–Al Coated Steel." Journal of Materials Engineering and Performance 28(1): 594-603.4. Chen, H., et al. (2018). "Comparative study of Zn–Mg–Al andAl–7Si coatings on the corrosion resistance of steel." Surface and Coatings Technology 333: 47-54.5. Yu, Y., et al. (2015). "Study on the Corrosion Behavior of a Zn–Mg–Al Coating on Cold-Rolled Steel." Materials 8(10): 7275-7288.。
ReviewRecent developments in advanced aircraft aluminiumalloysTolga Dursun a ,⇑,Costas Soutis ba Aselsan Inc,Ankara 06750,TurkeybAerospace Research Institute,University of Manchester,Manchester M139PL,UKa r t i c l e i n f o Article history:Received 16September 2013Accepted 2December 2013Available online 13December 2013Keywords:Aircraft structures Aluminium alloys Al–Li alloys CompositesMechanical propertiesa b s t r a c tAluminium alloys have been the primary material for the structural parts of aircraft for more than 80years because of their well known performance,well established design methods,manufacturing and reliable inspection techniques.Nearly for a decade composites have started to be used more widely in large commercial jet airliners for the fuselage,wing as well as other structural components in place of aluminium alloys due their high specific properties,reduced weight,fatigue performance and corrosion resistance.Although the increased use of composite materials reduced the role of aluminium up to some extent,high strength aluminium alloys remain important in airframe construction.Aluminium is a rela-tively low cost,light weight metal that can be heat treated and loaded to relatively high level of stresses,and it is one of the most easily produced of the high performance materials,which results in lower man-ufacturing and maintenance costs.There have been important recent advances in aluminium aircraft alloys that can effectively compete with modern composite materials.This study covers latest develop-ments in enhanced mechanical properties of aluminium alloys,and high performance joining techniques.The mechanical properties on newly developed 2000,7000series aluminium alloys and new generation Al–Li alloys are compared with the traditional aluminium alloys.The advantages and disadvantages of the joining methods,laser beam welding and friction stir welding,are also discussed.Ó2013Elsevier Ltd.All rights reserved.1.IntroductionThe cost reduction for aircraft purchase and operation has be-come a driving force in many airline companies.Cost reduction can be achieved by decreasing the fuel consumption,maintenance cost,operational costs,frequency of periodical controls and increasing the service life and carrying more passengers at a time.Therefore aircraft manufacturers are competing to meet the requirements of their airline customers.Weight reduction can im-prove fuel consumption,increase payload and increase range.Additionally,improved and optimised mechanical properties of the materials can result in increased period between maintenance and reduce repair costs.Since the material has a great impact on cost reduction,airframe manufacturers and material producers fo-cus on the development of new materials to meet customer requirements.Hence,a current challenge is to develop materials that can be used in fuselage and wing construction with improve-ments in both structural performance and life cycle cost.According to the design trials it is seen that an effective way of reducing the aircraft weight is by reducing the material density.It is found that the decrease in density is about 3–5times more effective than increasing tensile strength,elastic modulus or damage tolerance [1].Airframe durability is another parameter that directly affects costs.The cost of service and maintenance over the 30-year life of the aircraft are estimated to exceed the original purchase price by a factor of two [1].Therefore,both material producers and air-craft designers are working in harmony to reduce weight,improve damage tolerance,fatigue and corrosion resistance of the new metallic alloys.As a result,near future primary aircraft structures will show an extended service life and require reduced frequency of inspections.Composite materials are increasingly being used in aircraft pri-mary structures (B787,Airbus A380,F35,and Typhoon).Fig.1shows the increased usage of composites in several types of Boeing aircraft.The attractiveness of composites in the manufacturing of high performance structures relies on their superior mechanical properties when compared to metals,such as higher specific stiff-ness,specific strength (normalised by density),fatigue and corro-sion resistance.Although composites are thought to be the preferable material for wing and fuselage structures,their higher certification and production costs,relatively low resistance to im-pact and complicated mechanical behaviour due to change in envi-ronmental conditions (moisture absorption,getting soft/brittle when exposed to hot/cold environments)make designers to ex-plore alternative material systems.Fibre metal laminates such as GLARE which combines aluminium layers with glass fibre epoxy0261-3069/$-see front matter Ó2013Elsevier Ltd.All rights reserved./10.1016/j.matdes.2013.12.002⇑Correspondng author.Tel.:+903128475300.E-mail addresses:tdursun@.tr (T.Dursun),constantinos.soutis@ (C.Soutis).plies to improve tensile strength and more importantly damage tolerance arefinding great use in aerospace applications[3–12]. Impact resistance,effect of damage on stiffness/strength especially when loaded in compression and damage identification and detec-tion,in addition to joints,repair and recycling remain big chal-lenges for composites with the need of further research[13–18].Aluminium alloys have been the primary structural material for commercial and military aircraft for almost80years due to their well known mechanical behaviour,easiness with design,mature manufacturing processes and inspection techniques,and will re-main so for some time to come.However,the non-metallic mate-rials,despite the issues mentioned earlier,due to their superior specific strength properties provide a very competitive alternative, so aluminium producers need to keep investing and put great effort in improving the thermo-mechanical properties of the alu-minium alloys they produce.Density,strength,Young’s modulus,fatigue resistance,fracture toughness and corrosion resistance are all important parameters that need to be improved.Depending on the particular component under consideration,material properties have to outperform those offered by polymer composites.Chemical composition and processing control the microstructural features such as precipi-tates,dispersoids,degree of recrystallization,grain size and shape, crystallographic texture and intermetallic constituent particles. These properties affect the physical,mechanical and corrosion characteristics of aluminium alloys.Therefore material producers working closely with aircraft designers could design different types of metallic alloys where the physical and mechanical properties have been tailored to the specified needs.For instance,the upper side of the wing is mainly subjected to compression loading during flight,but also exposed to tension during static weight and taxiing, while the opposite happens to the lower part of the wing,hence careful optimisation of tensile and compressive strength properties is required.Damage tolerance,fatigue and corrosion resistance are and Alclad2524-T3sheet and2524-T351plate for the fuselage skin.They also developed7150-T7751extrusions for the support-ing members of the fuselage structure.The application of these materials saved thousands of pounds of weight for the Boeing 777[19].The aircraft manufacturers are also working to decrease the number of parts in new aircraft.These needs could be met by applying several approaches.Thefirst method is producing large and thick plates having fatigue and fracture characteristics equiv-alent to those of a thin plate.The second method is implementa-tion of joining technologies such as friction stir welding that allows the manufacture of large integrally stiffened panels that can be used for wing and fuselage skins[20].This review article covers the latest developments related to aluminium alloys used as aircraft primary structures and high-lights performance improvements in the2000,7000series alumin-ium alloys as well as the new generation of Al–Li alloys.Currently the7000series Al–Zn alloys are used where the main limiting de-sign parameter is strength;2000series Al–Cu alloys are used for fatigue critical applications since these alloys are more damage tol-erant,while Al–Li alloys are chosen where high stiffness and lower density are required.The advantages and disadvantages of the joining techniques,laser beam welding and friction stir welding, are also discussed.2.Developments in2000series Al–Cu aluminium alloysThe aluminium–copper(2000series)alloys are the primary al-loys used in airframe structural applications where the main de-sign criterion is damage tolerance.The2000series alloys containing magnesium have higher strength resulting from the precipitation of Al2Cu and Al2CuMg phases and superior damage tolerance and good resistance to fatigue crack growth comparedbination of materials used in Boeing Aircrafts.Thefigure is based on[2].T.Dursun,C.Soutis/Materials and Design56(2014)862–871863often the limiting design parameter[21].The wing can be considered as a cantilever type of beam that is loaded in bending duringflight but also torsion.The wing supports both the static weight of the aircraft and any additional loads subjected in service. Additional wing loads also come from the landing gear during taxiing,take-off and landing and from the leading and trailing edge theflaps and slats that are deployed during take-off and landing to create additional low speed lift.The upper surface of the wing is primarily loaded in compression because of the upward bending moment duringflight but can be loaded in tension while taxiing[21].Chemical compositions and mechan-ical properties of some of2000series aluminium alloys widely used in airframe design are given in Tables1and2 respectively.The2024-T3has been one of the most widely used alloys in fuselage construction.It has moderate yield strength,very good resistance to fatigue crack growth and good fracture toughness. The2024aluminium alloy remains as an important aircraft struc-tural material due to its extremely good damage tolerance and high resistance to fatigue crack propagation in T3aged condition. The low yield stress level and relatively low fracture toughness, limit the application of this alloy in the highly stressed regions [23].Microstructural effects on the fatigue properties of alumin-ium alloys are being investigated intensively.Improvements in compositional control and processing have continually produced new alloys.It is known that inclusions have substantial effects on the fatigue crack propagation.Higher fracture toughness values and better resistance to fatigue crack initiation and crack growth were achieved by reducing impurities,especially iron and silicon. It has been announced that for the fuselage applications the alloy 2524-T3has a15–20%improvement in fracture toughness and twice fatigue crack growth resistance of2024-T3[24].This improvement leads to weight savings and30–40%longer service life[25].The2524aluminium alloy has replaced the2024as fuse-lage skin in the Boeing777aircraft.Fatigue tests on the2524alloy showed that fatigue strength of this alloy is70%of the yield strength whereas for2024-T351fatigue strength is about45%of the yield strength[26].For the lower wing skin applications[27] the2224-T351and2324-T39alloys offer higher strength values compared to incumbent2024-T351with similar fracture tough-ness and corrosion pared to2024,both composi-tional and processing changes for2224-T351and2324-T39 alloys resulted in improved properties.A lower volume fraction of intermetallic compounds improved fracture toughness.For in-stance the maximum iron content is0.12%and silicon is0.10%in 2224-T351whereas in20240.50%for both impurities.A newly developed aluminium alloy2026is based on2024but it contains fewer impurities such as iron and silicon.Additionally,2026con-tains a small amount of zirconium which inhibits recrystallization [28].2026has higher damage tolerance,higher tensile strength, higher fatigue performance and acceptable fracture toughness compared to2024and2224[29].Although the contribution of Cu and Mg in intermetallic phases results in high strength however,due to the intermetallic phase particles the corrosion resistance of the alloy significantly drops. Several investigations have been done in order to increase both corrosion and fatigue resistance of2000series alloys[30–32].3.Developments in7000series Al–Zn aluminium alloysThe7000series of aluminium alloys show higher strength when compared to other classes of aluminium alloys and are selected in the fabrication of upper wing skins,stringers and horizontal/verti-cal stabilizers.The compressive strength and the fatigue resistance are the critical parameters in the design of upper wing structural components.The tail of the airplane,also called the empennage, consists of a horizontal stabilizer,a vertical stabilizer orfin,and control surfaces e.g.elevators and rudder.Structural design of both the horizontal and vertical stabilizers is essentially the same as for the wing.Both the upper and lower surfaces of the horizontal sta-bilizer are often critical in compression loading due to bending [21].High strength aluminium alloys such as the7075-T6are widely used in aircraft structures due to their high strength-to-weight ra-tio,machinability and relatively low cost.However,due to their compositions,these alloys are susceptible to corrosion.It is well known that corrosion reduces the life of aircraft structures consid-erably.During normal operation aircraft are subjected to natural corrosive environments due to humidity,rain,temperature,oil, hydraulicfluids and salt water.Among the issues facing ageing air-craft,corrosion in combination with fatigue is extremely undesir-able[27].The7000series alloys are also heat treatable,and the Al–Zn–Mg–Cu versions provide the highest strengths of all aluminium al-loys.Some of the7000series alloys contain about2%copper in combination with magnesium and zinc to improve their strength. These alloys although are the strongest they are the least corrosion resistant of the7000series.However,newer7000series alloys introduced have higher fatigue and corrosion resistance which may result in weight savings.Newer alloys such as the7055-T77, have higher strength and damage tolerance than the7075-T6[1]. The7475(Al–Zn–Mg–Cu)aluminium alloy is a modified version of7075alloy.The7475alloy is developed for applications that re-quire a combination of higher strength,fracture toughness and resistance to fatigue crack propagation both in air and corrosive environment.Both strength and fracture toughness properties of 7075alloy are improved by decreasing its contents of iron and sil-icon,and changing both quenching and ageing conditions.The to-tal iron and silicon content in7075is0.90%whereas in7475the total content is limited to0.22%.These changes in the7075alloy resulted in the development of the7475alloy which is having a fine grain size,optimum dispersion and highest toughness value among the aluminium alloys available at high strength level.It is also reported that the corrosion resistance and corrosion fatigue behaviour of the7475alloy are excellent.In general,its perfor-mance is better than that of much commercially available high strength aerospace aluminium alloys such as7050and7075alloys [23].Yield strength,%elongation,and K IC properties of widely used 2024and7075alloys are compared with7050and7475in Fig.2.It may be seen in Fig.2that the2024-T351alloy has high duc-tility and good fracture toughness(both in TL and LT orientations) but has relatively low yield strength.On the other hand,the7075 alloy under T651temper condition has yield strength of over 500MPa.The reported fracture toughness of this alloy(7075-T651)in TL and LT orientations is nearly24MPapm andTable1Chemical composition of some2000series aerospace aluminium alloys[22].2000Series Cu Zn Mg Mn Fe Si Cr Zr Ti Al2024 4.4– 1.50.660.560.50.1–0.15Remainder 2026 3.6–4.30.1 1.0–1.60.3–0.80.070.05–0.05–0.250.06Remainder 2224 4.1– 1.50.660.1560.12–––Remainder 2324 3.8–4.40.25 1.2–1.80.3–0.90.120.10.1–0.15Remainder 2524 4.0–4.50.15 1.2–1.60.45–0.70.120.060.05–0.1Remainder 864T.Dursun,C.Soutis/Materials and Design56(2014)862–871Alloy7050is another important alloy having the good balanceof strength,stress corrosion cracking(SCC)resistance and toughness.It is particularly suited for plate applications in the 76–152mm thickness range.Alloy7050exhibits better tough-ness/corrosion resistance characteristics than alloy7075because it is less quench sensitive than most aerospace aluminium alloys. The7050retains its strength properties in thicker sections while maintaining good stress corrosion cracking resistance and fracture toughness levels.Typical applications for alloy7050plates include fuselage frames and bulkheads where section thicknesses are 50–152mm.On the other hand alloy7050sheets are used in wing skins applications.Long-term controlled and in-service evaluations have shown that alloy7050plate and sheet products remain equal exfoliation and stress corrosion resistance at higher stress levels compared with other high strength aluminium alloys such as7075.A recent alloy,the7055-T7751(Al–8Zn–2.05Mg–2.3Cu–0.16Zr),has a yield stress that may exceed620MPa and the esti-mated weight saving attributed to its use for components in the Boeing aircraft777is635kg[34].This alloy provided a nearly 10%gain in strength,with higher toughness and significantly im-proved corrosion resistance[24].T77temper consists of three step ageing process that produces a higher strength and damage toler-ance combinations compared to7050-T76and7150-T651or T7751.The improved fracture toughness is a result of controlled volume fraction of coarse intermetallic particles and uncrystallized grain structure.Good combination of strength and corrosion resis-tance is attributed to the size and spatial distribution and the cop-per content of the strengthening precipitates.There exists a continuous improvement in the mechanical prop-erties of aerospace aluminium alloys.This has resulted in the development of high strength7xxx alloys(e.g.7075,7150,7055, 7449,in chronological order of application).These high strength al-loys are generally used in compression-dominated parts such as upper wing skins where damage tolerance considerations are sec-ondary.However,recent developments show that modifications in solute content and in particular in Zn/Mg/Cu ratios can enable the development of high strength products with significant improve-ments in damage tolerance such as AA7040,AA7140and AA7085.7085has been developed as the new generation high strength thick plate alloy to be alternative for7050/7010products. Due to the higher Zinc and lower Cu contents,higher fracture toughness and slow quench sensitivity were obtained.This product was selected for wing spar applications on the Airbus A380.There is also an effort to obtain a good combination of high strength and good corrosion resistance through the applications of different heat treatment methods[35].Two important metallurgical princi-ples resulting in improvements are:a decrease in the Mg/Zn ratio, and an overall reduction in saturation of the composition with re-spect to the theoretical maximum solubility.The strong impact of Mg concentration increases on strength(beneficial)and on tough-ness(detrimental)is well known.The basis of the Mg/Zn adjust-ments is the observation that a partial replacement of Mg with2024-T3517050-T736517075-T6517475-T7351 Yield Strength% Elongation Kıc TL Direction Kıc LT Directionrepresentation of yield strength,%elongation,andalloys.The is based[23].Fig.3.S–N curves for different aluminium alloys[23].T.Dursun,C.Soutis/Materials and Design56(2014)862–871865Zn(a slightly less effective hardener per wt.%)enables an increase in toughness while maintaining adequate strength.The overall reduction in solute saturation directly affects the quench sensitiv-ity,which is critical for damage tolerance properties of high solute alloys.AA7056-T79,developed for the upper wing skin of large commercial aircraft is good example of the improvements in strength-toughness balance[34].On the other hand the addition of Mn and Zr in aluminium alloys can formfine dispersoids which affect recrystallization characteristics and grain structure.These dispersoids retards recrystallization and grain growth.Zr content in aluminium alloys can form A13Zr dispersoid,which have a rela-tionship with the matrix and significantly refines the grain size. The addition of Zn increases the strength of the alloy,whereas the addition of Mn increases the fracture toughness of the alloy due to the formation of the secondary phase containing Mn and Fe,which decreases the adverse effects of Fe on fracture toughness [36].Chemical composition of some of the important7000series aluminium alloys are given in Table3.Fretting,a special type of wear process that occurs at the con-tact area between two materials under load and subject to very small amount of relative motion,is another important issue needed to be understood in bolted/pinned aircraft joints.There is a current focus on the prevention of fretting in the aerospace industry since due to fretting,cracks can initiate at stresses(fret-ting zone),well below the fatigue limit of non-fretted materials and the structure’s resistance to fatigue can be decreased by50–70%.Introduction of compressive residual stresses at the surface of hole,reduction in coefficient of friction,increased surface hard-ness,changing the surface chemistry and increasing the surface roughness are the main methods that are applied to reduce the nucleation and growth of fretting cracks and improve the fatigue life of aerospace joints and improve fretting resistance[37–42]. 4.Developments in aluminium–lithium alloysReducing the density of materials is accepted as the most effec-tive way of lowering the structural weight of aircraft.Li(density 0.54g/cm3)is one of the few elements that have a high solubility in aluminium.This is significant because,for each1%added,the density of an aluminium alloy is reduced by3%.Lithium is also un-ique amongst the more soluble alloying elements in that it causes a considerable increase in the elastic modulus(6%for each1%Li added).Additional advantage is that,aluminium alloys containing Li respond to age hardening[43].The use of aluminium–lithium(Al–Li)alloys in aerospace appli-cations goes back to1950s with the development of alloy2020.In the1980s,2nd generation of Al–Li alloys were developed.The sec-ond generation alloys included the2090,2091,8090and8091.The Al–Li alloys2090,2091,8090and8091contain1.9–2.7%lithium, which results in an about10%lower density and25%higher spe-cific stiffness than the2000and7000series alloys.However,due to technical problems such as anisotropy in the mechanical prop-erties,low toughness,poor corrosion resistance,manufacturing is-sues(hole cracking and delamination during drilling),2nd generation Al–Li alloys did notfind wide use in aircraft industry. The anisotropy experienced by these alloys is a result of the strong crystallographic textures that develop during processing,with the fracture toughness problem being one of primarily low strength in the short transverse direction[1,21,44,45].The pressure for higher strength and improved fracture tough-ness with reduced weight in aircraft applications have resulted in the development of new generation of Al–Li alloys.The new gener-ation of Al–Li alloys provides not only weight savings,due to lower density,but also overcomes the disadvantage of the previous prob-lems with increased corrosion resistance,good spectrum fatigue crack growth performance,a good strength and toughness combi-nation and compatibility with standard manufacturing techniques. This results in well-balanced,light weight and high performance aluminium alloys[1,44,46].In the new generation(3rd)Al–Li alloys Li concentration was reduced to0.75–1.8wt.%.The addition of alloying elements in the3rd generation Al–Li alloys is used to improve the mechanical properties.Poor corrosion resistance of 2nd generation Al–Li alloys is eliminated in3rd generation Al–Li alloys by optimising alloy composition and temper.Also Zn additions improved corrosion resistance.The additions of Cu,Li and Mg form the strengthening precipitates and small additions of the dispersoid-forming elements Zr and Mn control the grain structure and crystallographic texture during thermo-mechanical processing.Crack deviation occurs due to high crystallographic texture in addition with slip planarity.Deviation from expected direction of crack propagation makes it difficult to define inspec-tion points and the positioning of crack arresters.It was found that in addition to reduction of the texture components,the severity of slip planarity had to be decreased.This reduction was achieved by decreasing the amount of(Al3Li)phase.This can be achieved by keeping the amount of Li additions below1.8wt ptc.The fracture toughness of2nd generation Al–Li alloys was often lower than the incumbent2024alloy products for designs where damage toler-ance is the driving parameter.It was determined that fracture toughness is affected only by insoluble second-phase particles.In 3rd generation Al–Li alloys like2199this disadvantageous condi-tion was eliminated by composition optimisation,thermal–mechanical processing and precipitate microstructure control.Chemical compositions and mechanical properties of some of the widely used Al–Li alloys are shown in Tables4and5 respectively.Alloy2195,a new generation Al–Li alloy,has a lower copper content and has replaced the2219for the cryogenic fuel tank on the space shuttle where it provides a higher strength,higher mod-ulus and lower density than the2219.Other alloys,including the 2096,2097and2197,also have lower copper contents but also have slightly higher lithium contents than2195[1].New genera-tion of Al–Li alloys have higher Cu/Li ratio than the second gener-ation alloys(2090and2091)as illustrated in Fig.4.The new generation of2199Al–Li alloys sheet and plates found applications in the aircraft for fuselage and lower wing applica-tions,respectively and the2099extrusions for internal structure. It was determined that the2199-T8E79plate for the lower wing skin,the2099-T83extrusions for lower wing stringers and the 2199-T8prime sheet for fuselage skin would provide the most benefit for the given applications examined.It is stated that com-pared to2024,the2199plates have lower density,significantly better stress corrosion and exfoliation corrosion resistance,signif-icantly better spectrum fatigue crack growth performance,betterTable3Chemical composition of some7000series aerospace aluminium alloys[22].7000Series Cu Zn Mg Mn Fe Si Cr Zr Ti Al7050 2.3 6.2 2.25–60.1560.12–0.1–Remainder 7055 2.0–2.67.6–8.4 1.8–2.30.050.150.10.040.08–0.250.06Remainder 7075 1.2–2.0 5.1–6.1 2.1–2.90.30.50.40.18–0.28–0.2Remainder 7150 1.9–2.5 5.9–6.9 2.0–2.70.10.150.120.040.08–0.150.06Remainder 7475 1.2–1.9 5.2–6.2 1.9–2.60.060.120.100.18–0.25–0.06Remainder 866T.Dursun,C.Soutis/Materials and Design56(2014)862–871toughness,and higher tensile yield and compressive yield strengths.The ultimate tensile strength,bearing and shear strengths for the T8E80temper are similar to those for 2024,while for the T8E79temper,these strengths tend to be lower.However,this reduction in tensile yield strength provides the higher spec-trum fatigue crack growth performance.Thus,one of the two tem-pers of 2199may be more suitable for a given application,depending on the design criterion [44].Al–Li 2099alloy has low density,high stiffness,superior dam-age tolerance,excellent corrosion resistance and weldability for use in aerospace structures that require high strength.Alloy 2099extrusions can replace 2xxx,6xxx,and 7xxx aluminium alloys in applications such as statically and dynamically loaded fuselage structures and lower wing stringers.2nd generation Al–Li alloys were susceptible to cracking and delamination during installation of interference fit fasteners as a result of cold working.Low elonga-tion and work hardening properties were the results of these prob-lems.In the 3rd generation Al–Li alloys elongation and cold working capability were improved.Alloy 2099extrusions have good machining,forming,fastening,and surface finishing proper-ties.The 2099plate and forgings have better strength,modulus,density and corrosion performance than the7075-T73and 7050-T74plate products.The T8E67temper has much higher strength than the 2024-T3511or 2026-T3511with better toughness,much better corrosion resistance (Fig.5)and lower density.The fatigue crack growth resistance of alloy 2099also shows improvement with respect to the 2024-T3511,which has been a baseline alloy for fatigue critical components [47].The effects of normal heat treatments and thermomechanical heat treatments on the mechanical properties and fracture tough-ness of the 2A97new generation Al–Li alloy were studied by Yuan et al.[48].The aim was to improve the relationships of strength,ductility and fracture toughness,and make possible their applica-tions in the aeronautical industries.The Al–Li 2A97alloy was developed primarily in an attempt to be used for plates and for-gings as a promising aerospace material.It was stated that the problem with this alloy is that it yields low ductility and fracture toughness in T8temper with a high tensile strength,and it yields low strength in T6temper with a high ductility and fracture tough-ness.With 4%deformation after low temperature underaging,the ductility and fracture toughness were improved for the 2A97alu-minium–lithium alloy.The K q value of 43.5MPa pm in the T8tem-per higher than that of 42.5MPa pm in the T6temper was obtained,by heat-treatment process and thermomechanical heat-treatment process [48].Another new generation Al–Cu–Li alloy 2050was developed to replace the 2000series and 7000series alloys where medium to high strength and high damage tolerance are needed [49].Strength,corrosion resistance,fatigue initiation and crack growth resistance properties were compared and according to the test re-sults it was concluded that the 2050-T84alloy in addition to its density benefit,offers improvements over the 2024-T351in sta-tic-related properties and corrosion resistance.When compared to incumbent alloy 7050-T7451,the 2050-T84offers an improved (strength,toughness)balance,at 5%lower density and significantlyimproved stress corrosion resistance without any redesign and when strength,stiffness and fatigue properties are taken into ac-count,it can lead to weight reduction up to a total of about 10%,depending on the part design drivers.Al–Li alloy 2198was developed to replace 2024and 2524in air-craft structures where damage tolerance is the critical design fac-tor.It has a wt.%Cu composition ranging from 2.9%to 3.3%and respective of Li from 0.9%to 1.1%.Under constant amplitude load-ing and stress ratio R =0.1the fatigue endurance limit is almost 40%below the 2024yield stress,while for 2198-T351is only 8%lower than the respective yield stress.When taking into account density,2198is superior to 2024in high cycle fatigue and fatigue endurance limit regimes.For the same normalised applied stresses,2198was observed to absorb 2–3times more energy to fracture than 2024[50,51].Comparing the fatigue results in air it was ob-served that 2524-T3presented a higher fatigue strength and fati-gue limit than the 2198-T851Al–Li alloy.However,when the alloys were pre-corroded in saline environment they presented similar fatigue behaviour [52].2060and 2055are the newest 3rd generation Al–Li alloys.2060has 0.75wt.%of Li,3.95wt.%of Cu and 0.85wt.%of Mg whereas 2055has 1.15wt.%of Li,3.7wt.%of Cu and 0.4wt.%of Mg.The wt.%of the other alloying elements are approximately same for these two alloys.These alloys show improved strength/toughness relationship.Additionally,these alloys exhibit good thermal stability.Both 2055and 2060have excellent corrosion performance compared to that of common aerospace aluminium alloys such as 2024-T3and 7075-T6.Therefore,these alloys could be alternative materials for fuselage,lower wing and upper wing constructions.Trade study analyses show that implementation of Al–Li alloys can save significant weight over the baseline 2000and 7000series aluminium alloys.For instance for fuselage skin applications 2060-T8can save 7%weight compared to that of 2524-T3,for lower wing skin applications 2060-T8can save 14%weight compared to that of 2024-T351and for upper wing skin and stringer applications,2055-T8can save 10%weight compared to that of 7055-T7751[47,53].The 3rd generation Al–Li alloys offers up to 10%weight savings,lower risk and 30%less expensive to manufac-ture,operate and repair than composite-intensive planes.In addition,these alloys can provide passenger comfort features that are equivalent to composite-intensive planes,such as largeTable 4Chemical composition of some Al–Li alloys [22].Al–Li alloys Li Cu Zn Mg Mn Fe Si Cr Zr Ti Others 20500.7–1.3 3.2–3.90.250.2–0.60.2–0.50.10.080.050.06–0.140.10.2–0.7Ag 2090 1.9–2.6 2.4–3.00.10.250.050.120.100.050.08–0.150.15–20980.8–1.3 3.2–3.80.350.25–0.80.350.150.12–0.04–0.180.10.25–0.6Ag 2099 1.6–2.0 2.4–3.00.4–1.00.1–0.50.1–0.50.070.050.1–0.50.05–0.120.10.0001Be 2199 1.4–1.8 2.0–2.90.2–0.90.05–0.40.1–0.50.070.05–0.05–0.120.10.0001Be 80902.2–2.71.0–1.60.250.6–1.30.100.300.200.100.04–0.160.1–Table 5Mechanical properties of some Al–Li alloys [22].Al–Li alloys UTS (MPa)Yield Strength (MPa)Fracture Toughness,K IC (Mpa m 1/2)Elongation (%)2050-T8454050043(LT)NA 2090-T8353148343.932098-T82503476NA 62099-T8354352030(LT)7.627(TL)2199-T840034553108090-T85150045533(LT),30(TL)1212.4(SL)T.Dursun,C.Soutis /Materials and Design 56(2014)862–871867。
