Microstructures and properties of high-entropy alloys

1.1 Metals and Non-metalsWords and termsdefinite－确定的、明确的defect－缺陷plastic deformation塑性变形stress concentrator 应力集中点self-strengthening自强化the tip of a crock裂纹尖端☐Among numerous properties possessed by materials，their mechanical properties，in the majority of cases，are the most essential and therefore，they will be given much consideration in the book．☐在一些主要应用场合，机械性能是材料的各种性能中最重要的性能，因此，本书中将重点讨论。

▪consideration 考虑，需要考虑的事项，报酬☐All critical parts and elements，of which a high reliability （可靠性）is required，are made of metals, rather than of glass，plastics or stone.☐由于各种关键零部件的可靠性要求高，均用金属而不是玻璃、塑料或石头制造。

▪is required 翻译时将英文中的被动语态，改译为汉语中的主动语态。

▪rather than 而不是☐As has been given in Sec.1-1，metals are characterized by the metallic bond（金属键），where positive ions （正离子）occupy the sites of the crystal lattice （晶格）and are surrounded by electron gas（电子云）．☐正如Sec1-1中所说，金属主要由金属键组成（其特征主要……）。

材料科学与工程学院费维栋工学博士哈尔滨工业大学材料科学与工程学院副院长教授/博士生导师+86-451-86413908wdfei@主要研究方向[1]多功能金属基复合材料—低热膨胀、高成型性、高塑性、低成本铝基复合材料的界面设计与塑性变形行为与机制研究；高热导、低膨胀、高电导铜基和铝基复合材料的界面设计与性能优化。

[2]功能薄膜材料—主要包括铁磁薄膜、铁电薄膜、压电薄膜的制备、多铁薄膜等的微结构表征和性能分析；铁性薄膜的铁性相变理论、磁电耦合机制的理论与试验研究。

[3]材料的X射线衍射与散射分析理论与方法研究—主要包括：纳米薄膜材料的织构、残余应力、标度特性、生长机制、界面行为等的分析；块体材料织构、残余应力、缺陷等的表征。

社会兼职教育部材料物理与化学专业教学指导委员会委员黑龙江省复合材料学会常务理事《分析与测试技术学报》和《试验技术与试验机》编委全国X射线衍射专业委员会委员东北三省X射线分析学会副主任委员主要学术成果1.W.D.Fei,H.Y.Yue,L.D.Wang,Equicohesive temperature of the interface and matrix and its effect on the tensileplasticity of Al18B4O33whiskers reinforced aluminum composite at elevated temperatures,Materials Chemistry and Physics,2010,119(3),515-5182.Q.G.Chi,W.L.Li,C.Q.Liu,W.D.Fei,Effect of TiOx seed layer on the texture and electric properties in La and Camodified PbTiO3thin films,Thin Solid Films,2009,517(17),4826-48293.Q.G.Chi,W.L.Li,B.Feng,C.Q.Liu and W.D.Fei,Low-temperature crystallization and orientation evolution ofNb-doped Pb(Zr,Ti)O3thin films using a Pb0.8La0.1Ca0.1Ti0.975O3seed layer,Scripta Materialia,2009,60(4),218-2204.W.D.Fei,C.Q.Liu,M.H.Ding,et al.Characterization of fiber texture by omega-scan x-ray diffraction,Review of ScientificInstruments,2009,80(9),0939035.Q.G.Chi,W.L.Li,W.D.Fei,Enhanced performance of sandwich structure Pb0.8La0.1Ca0.1Ti0.975O3thin film for pyroelectricapplications,Materials Letters,2009,63(20),1712-17146.Y.S.Yu,Hai-Bo Li,W.L.Li,Mei Liu,Yu-Mei Zhang and W.D.Fei，Structure and magnetic properties ofmagnetron-sputtered FePt/Au superlattice films，Journal of Physics D:Applied Physics，2008,41,2450037. C.Q.Liu,W.D.Fei,W.L.L，Theory of magnetoelectric coupling in2-2-type magnetostrictive/piezoelectric compositefilm with texture，Journal of Physics D:Applied Physics，2008,41(12),1254048. C.Q.Liu,W.D.Fei,W.L.L,Effects of texture and residual stress on the transition of ferroelectric perovskite thin filmswith C-axis polarization,Thin Solid Films,2008,516(6),1256-12709.H.Y.Yue,W.D.Fei,L.D.Wang,Effects of heat-treatment on interfacial microstructures and tensile properties ofZnAl2O4and ZnO coated Al18B4O33w/Al composites,Materials Science and Engineering A:Structural Material Properties Microstructure and Processing,2008,472(1-2),231-23410.Z.J.Li,W.D.Fei,H.Y.Yue,et al.Hot deformation behaviors of Bi2O3-coated Al18B4O33whisker reinforced aluminummatrix composite with high formability,Composites Science and Technology,2007,67(6),963-97311. F.Yang,W.D.Fei,Z.M.Gao,et al.An alternative micro-area X-ray diffraction method for residual stress measurement ofPb(Zr,Ti)O-3film,Surface&Coating Technology,2007,202(1),121-12512.H.Y.Yue,W.D.Fei,L.D.Wang,Mechanical properties and thermal stability of ZnAl2O4-coated aluminum boratewhiskers reinforced2024Al composite,Journal of Materials Science,2008,43(18),6233-623713.H.Q.Gao,L.D.Wang,W.D.Fei,Interfacial reaction and tensile strength of copper-coated Al18B4O33whisker reinforced6061Al composite,Materials Science and Engineering A:Structural Material Properties Microstructure and Processing,2008,479(1-2),261-26814.Z.J.Li,L.D.Wang,W.D.Fei,Effect of interfacial Bi2O3coating on compressive deformation behavior of aluminumborate whisker-reinforced aluminum composite at elevated temperature,Materials Science and Engineering A: Structural Material Properties Microstructure and Processing,2007,447(1-2),314-31815.H.Y.Yue,W.D.Fei,Z.J.Li,Effects of ZnO coating on the wettability and tensile properties of aluminum boratewhisker-reinforced aluminum composite,Materials Science and Engineering A:Structural Material Properties Microstructure and Processing,2006,441(1-2),197-20116.王黎东，费维栋，含铝和／或镁的复合硅酸盐的制备方法专利号：03132477.017.费维栋，岳红彦，王黎东，含SnO2涂覆陶瓷相增强铝基或镁基复合材料专利号：200510010130.418.费维栋，岳红彦，王黎东，ZnAl2O4包覆硼酸铝晶须增强铝基或镁基复合材料及其制专利号：200510127326.119.费维栋，岳红彦，王黎东，ZnO涂覆的陶瓷相增强铝基或镁基复合材料及其制备方法专利号：200510127309.820.王黎东，费维栋，β-锂霞石的制备方法专利号：200610009821.721.王黎东，费维栋，含β-锂霞石的铜基复合材料专利号：200610009820.222.费维栋，王黎东，一种含β-锂霞石的铜基复合材料的制备方法专利号：200710144909.423.费维栋，李志军，王黎东，三氧化二铋包覆陶瓷相增强铝基复合材料专利号：200510009684.2。

诚信声明本人郑重声明：本论文及其研究工作是本人在指导教师的指导下独立完成的，在完成论文时所利用的一切资料均已在参考文献中列出。

本人签名：年月日毕业设计任务书设计题目：T8钢热处理工艺及组织性能研究系部：机械工程系专业：材料成型及控制工程学号：1120182 37 学生：指导教师（含职称）：（副教授）1．课题意义及目标学生应通过本次毕业设计，运用所学过的金属学及热处理等专业知识，了解T8钢的概况；熟悉T8钢的热处理工艺方法；认识T8热处理前后金相组织；找出热处理对T8钢组织和力学性能的影响规律，为优化热处理工艺提高零件质量提供一定的理论依据。

2．主要任务（1）制定T8钢热处理工艺，进行热处理实验。

（2）制备金相试样，观察分析T8钢热处理前后的显微组织。

（3）测定T8钢热处理前后力学性能，包括拉伸性能、硬度、冲击韧性等。

（4）分析热处理工艺、组织结构与力学性能之间的关系。

（5）撰写毕业论文。

结构完整，层次分明，语言顺畅；避免错别字和错误标点符号；格式符合太原工业学院学位论文格式的统一要求。

3．主要参考资料[1] 刘旭麟，高路斯，刘顺华，等.T8钢淬火热处理组织的计算机模拟研究[J].热加工工艺，2006，35（6）：44-46.[2] 王英杰，孙国宏. T8钢最佳预处理工艺的选择[J]. 热加工工艺，1995，（4）：55-55.[3] 张玉琴，王谦，王玉琴. 改善碳素工具钢组织性能方法探析[J]. 河南冶金，2001，（05）：10-10[4]王能为，孙艳. T8钢形变球化退火工艺[J]. 南方金属，2009，（166）：23-25[5] 崔忠圻，覃耀春.金属学与热处理[M]. 北京，机械工业出版社，2007：230-308[6] 王佳杰，莫淑华，等，工程材料力学性能[M].北京：北京大学出版社，2013,3[7] 束德林，等，工程材料力学性能[M]，机械工业出版社，2003.7[8] 那顺桑，李杰，艾立群，等金属材料力学性能[M]，冶金工业出版社2011.74．进度安排审核人： 2015 年 1 月 16 日T8钢热处理工艺及组织性能研究摘要：本次实验主要研究热处理工艺对T8钢力学性能的影响。

HIGH STRENGTH SHEET AND PLATE STEELS FOR OPTIMUM STRUCTURAL PERFORMANCEJan-Olof SperleSSAB Tunnplåt AB, Borlänge, SwedenSUMMARYModern quench and tempering as well as continuous annealing make it possible to produce high strength steel with up to 1200 MPa yield strength. This high yield strength gives potential for considerable improvements in performance and reduction in weight, which are of increasing importance in the transport sector and in vehicles used in the construction industry.This paper describes briefly the static properties, forming, joining and structural strength characteristics as well as crash resistance and energy absorption of high strength steels. Examples of applications are given. Special attention is paid to extra high strength and ultra high strength steels. Conventional forming and joining methods can be used. By taking into account the qualities and characteristics of high strength steel at the design stage and in production technique the full potential of the material can be utilized.INTRODUCTIONIndustry, particularly in the transport sector, is constantly aiming to reduce weight, increase performance and safety and rationalize production methods. The use of high strength steels with good formability and weldability is increasingly seen as one important way in which these aims can be met. Quenched and tempered steels with yield strength levels up to 1100 MPa and hot rolled cold forming steels with yield strength levels up to 740 MPa are successfully used in cranes, trucks, dumpers, temporary bridges and similar products. For automotive applications rephosphorized, micro-alloyed and dual-phase cold rolled grades with tensile strengths of up to 1400 MPa and metallized grades with tensile strengths of up to 600 MPa have been introduced.On the basis of yield strength new types of high strength steels give a great potential for weight reduction and cost effective designs. To exploit the fullpotential of high strength steels the design philosophy and production techniques must take into accont factors such as formability, weldability, stiffness, buckling, crush resistance and fatigue.In this paper the high strength steels will be presented with focus on the higher strength levels. The above factors are exemplified and discussed on the basis of optimum structural performance in using high strength steels. Most of the test results presented in this paper refer to cold rolled high strength sheet steel, however, many aspects of the use of these steels are generally applicable. Applications are presented where different high strength steels are successfully used.THE MOTIVES FOR USING HIGH STRENGTH STEELSThe driving forces behind the increasing use of high strength steels are often connected to the wish to achieve the best structural performance at the lowest possible weight and cost. In general, overall economy of the final product is usually the deciding factor. This is based on material cost, production economy and, increasingly, Life Cycle Costs - an analysis of all the costs and benefits during the entire life of the product.In such an analysis one should for example consider that by using high strength steel it is possible to reduce material thickness and dead weight of a structure which in turn give higher pay-loads. Lower production weights lead to lower handling costs and less filler material in welding operations. Additionally, modern high strength steels combine several favourable properties such as high strength, weldability, excellent forming and punching characteristics and minor variations in physical properties. All these factors are of primary importance in keeping production costs down. The environmental advantages of low weight and increased pay-load are also extremely important today when fuel consumption, exhaust emissions and the use of finite global resources must be kept to a minimum.The use of high strength steel usually leads to lower material costs since the weight reduction more than compensates for the higher price of high strength steel. This means that there is a strong motivation to use high strength steels outside the transport sector and in structures that are regarded as ”simple” such as shelf systems and hinges.STEEL GRADESAll high strength steel grades produced at SSAB are made by basic oxygen furnace steelmaking followed by continuous casting. Inclusion control is used to increase formability. Steel gradesand mechanical properties are shown in Table I. This paper primarily refers to Extra High Strength, EHS (450 ≤ R e≤ 800 MPa) and Ultra High Strength, UHS (R e > 800 MPa) steels. When placing steels in these groups the yield strength for DP steels is the one after 2 % work-hardening and bake-hardening.Table I: Mechanical properties for high strength steel gradesGrade Steel1typeYieldstrength(MPa)Tensilestrength(MPa)Elongation(%)E c2 minminA5 min A80minWeldox 500 HR-MA 500 570 16 - .39 Weldox 700 HR-MA 700 780 14 - .38 Weldox 900 HR-MA 900 940 12 - .56 Weldox1100 HR-MA 1100 1200 10 - .68 Domex 350 YP HR-MA 350 430 26 - .17 Domex 490 XP HR-MA 490 550 18 - .33 Domex 590 XP HR-MA 590 650 15 - .32 Domex 690 XP HR-MA 690 750 15 - .32 Domex 740 XP HR-MA 740 790 13 - .37 Docol 350 YP CR-MA 350 410 - 22Docol 500 YP CR-MA 500 570 - 12Docol 600 DP CR-DP 350 600 - 16Docol 800 DP CR-DP 500 800 - 8Docol 1000 DP CR-DP 700 1000 - 5Docol 1200 DP CR-DP 1000 1200 4Docol 1400 DP CR-DP 1200 1400 3Dogal 350 YP HDG-MA350 420 - 22Dogal 500 YP HDG-MA500 600 - 101) HR = hot rolled MA = microalloyedCR = cold rolled DP = dual-phaseHDG = hot-dip galvanized2) Ec = C + Mn6+ Cr Mo V++5+ Ni Cu+15(Carbon equivalent, typical values)The Weldox grades are produced in thicknesses 5 - 80 mm. Domex grades are produced in thicknesses 2 - 10 mm and Docol and Dogal in 0.5 to 2 mm.The Weldox grades are either thermomecanically processed (Weldox 500) or quenched and tempered (Weldox 700 - 1100) hot rolled microalloyed steel plates.Domex grades are all hot rolled thermomecanically processed microalloyed strip steels. Docol grades are either cold rolled microalloyed steels (Docol 350 - 500 YP) or cold rolled dual-phase steels (Docol 600 - 1400 DP). Dogal grades, finally, are hot-dip galvanized microalloyed steels.FORMABILITYAll grades mentioned above are intended for cold forming without any extra heating. A low level of non-metallic inclusions and sulphide-shape control are very important for bend formability and edge ductility in hole expansion.A Domex 690 XP hot-rolled grade can be bent without cracks to a bending radius of 1.6xt (t = sheet thickness). The corresponding value for Weldox 700 is 2xt.The dual-phase grades can be work-hardened after forming and bake-hardened after paint baking to increase the yield strength by up to a maximum of 300 MPa. Press-forming can be used even on the tensile strength level 1400 MPa but rollforming is the most suitable method for forming Docol 1200 DP and Docol 1400 DP. The press formability of Docol 600 - 1400 DP in comparison with mild steel is illustrated in Figure 1 [1].Fig 1 Examples from tests in deep drawing and stretch forming of steels DC O4 (mild steel), Docol 600 DP, Docol 800 DP, Docol 1000 DP,Docol 1200 DP and Docol 1400 DPPress hardening using the Plannja process, where boron steel sheets are hot formed in cooled tools, is a very interesting alternative to cold forming for complicated parts of very high strength (R e = 1200 MPa).WELDABILITYAll grades described in this paper can be welded with conventional welding methods. The reason for the good weldability is the lean chemistry of the steels.The most common welding methods for hot rolled steel grades are manual metal arc (MMA) and gas shielded arc welding (MAG). For cold rolled and metallized grades spot welding and MAG-welding are most frequently used. When discussing weldability of high strength steels the matter of most concern is normally cold cracking in the heat affected zone (HAZ). Brittle microstructures such as martensite of high carbon content and high levels of hydrogen together with high restraint forces increase the risk of cold cracking. The carbon equivalent CE, being a measure of the richness in chemical composition, is often used as a value to estimate the susceptibility to cold cracking. If the CE-values given in table I are compared to the CE-value of 0.4 for an ordinary standard high strength steel St 52-3 (R e = 350 MPa) it is obvious that Weldox and Domex extra high strength steels normally show little risk of cold cracking. For plate thicknesses greater than 10 mm preheating is recommended when working with Weldox 900 and 1100. The weldability of Weldox and Domex steels is discussed in more detail in [2] and [3].All Docol cold rolled and Dogal metallized products can be MAG-welded or spot welded, but, it is important to adjust the welding parameters according to the alloy content of each grade. For Docol 1200 DP and 1400 DP only spot welding to mild steel is recommended.MMA- and MAG-welded EHS and UHS steels often show a narrow soft zone in HAZ. In the case of Weldox QT grades and Docol DP grades this is mainly due to tempering and in Domex, Docol and Dogal microalloyed grades due to loss of precipitation hardening in the microstructure. If the soft zone is small in comparison to the thickness of the plate or sheet the strength of the welded joint is not effected due to the high degree of constraint.The width of the soft zone depends mainly on heat input and the thickness. Low heat input is therefore recommended when welding EHS and UHS steels which have a structural load perpendicular to the weld. In such cases it is also advisable to choose a welding wire which matches the strength of the material to be welded.Tensile test results on butt welded joints in Domex cold forming steel and Docol cold rolled steels are shown in Figure 2. It can be seen that the tensile strength of the MAG-welds in Docol DP steels is somewhat lower than the base metal strength when the tensile strength exceeds 800 MPa. The lowertensile strength.STIFFNESSThe use of high strength steel often leads to weight and thickness reductions. Since the Young’s modulus is the same for high strength steel and mild steel the stiffness decreases when the material thickness is reduced. If this reduction is not acceptable the stiffness loss can be compensated by changing the shape of the section.Fig 3 Reduced weight and cost with unchanged stiffnessFigure 3 illustrates that a small increase in section height of a beam can compensate for the stiffness loss associated with a thickness reduction, the stiffness being proportional to the square of the section height. This is a very clear example of the advantage of thinking in terms of the properties of high strength steel at the design stage.BUCKLINGDecreased thickness can result in buckling. The governing parameter for buckling is the width to thickness ratio (w/t) rather than the absolute thickness. This means that the risk of buckling is the same for a 1 mm thick sheet in an automotive structure as in a 20 mm thick bridge structure if the value of w/t is the same. The critical value of the width to thickness ratio, over which buckling will take place before the yield load is reached, is related to the yield strength by(w/t)cr = C √1 Rewhere (w/t)cr = critical width to thickness ratioC = constant depending on overall geometry R e = yield strength (MPa)Cross sections which buckle before the nominal stress in the flanges reaches the yield strength are categorised in cross section class 3 [4]. Cross sections that can be bent plastically without buckling are categorised in section class1 and cross sections in between those limits in section class 2. The value ofC for the limit between section class 2 and 3 is C = 200 for flanges in I, T, CIn order to take full advantage of the properties of high strength steel, cross sections should be in section class 1 or 2. For sections in section class 3 there is, however, still the positive effect of increased yield strength on the load-bearing capacity although it will be somewhat reduced by buckling.FATIGUEWhen introducing high strength steels into fatigue loaded structures it is important to note that the fatigue strength of welded joints does not normally increase with the increasing base metal strength. The reason for this is that the crack-like defects that are present at the weld toes mean that crack propagation will feature in the major part of the fatigue life. Since the crack growth resistance does not differ between mild steel and high strength steel, neither does the fatigue strength of the welded joints. This is illustrated in Figure 5 where we also see that if the stress concentration is low or moderate as in holes, radii and recesses, a decreased thickness and a higher working stress can be balanced by the higher fatigue strength of the high strength steel.The fatigue strength for unnotched base metal is strongly related to the surface roughness. Domex grades normally have a surface roughness R a ≈ 2 and Weldox grades R a = 4 - 8 [5].1002003004005006001002003004005006007008009001000Yield strength (MPa)F a t i g u e s t r e n g t h (M P a )Fig 5 Fatigue strength as a function of yield strengthIn order to achieve optimum performance of high strength steels in fatigue loaded welded structures, welds should be sited in areas of low stress. For spot welds the electrode diameter can be increased and the spot pitch reduced. For butt and fillet welds the toe of the weld can be ground or TIG-dressed in order that the fatigue strength of the weld may be adapted to the high strength steel. [4, 6].CRASH RESISTANCE - ENERGY ABSORPTIONTougher safety standards, for example regarding crash resistance of cars, have highlighted the interest in extra high strength and ultra high strength cold rolled, metallized and thinner hot rolled sheet steels. These steels are effective both for absorbing large amounts of energy, as in the front and rear of a car, and for withstanding high peak loads, as in the structure constituting the passenger compartment.In order to increase knowledge of how yield strength, thickness and overall geometry influence the energy absorption, static and dynamic tests in axial compression and bending have been performed on different sections.These tests, summarized below, are described in more detail in [7, 8, 9]. Axial crush testsStatic and dynamic axial tests have been performed on DP steels. The test specimens were 300 mm long rectangular hollow sections, 60x60x1.2 mm, developing an accordion-like deformation pattern when loaded in axial compression. The specimens were manufactured by joining two formed U-sections together by gas metal arc welding. Impact loads were achieved by accelerating steel pistons in a horizontal tube to the predetermined speed, 50 km/h.As expected, the absorbed energy increases with the increasing tensile strength of the steel grade, Figure 6.A comparison of results for static and dynamic tests confirm that there is a positive effect of crush speed for all steels including UHS-steels. This means that all these steels have a positive strain rate sensitivity.in DP steelsBending testsBending tests related to the application of high strength steels, for example in door intrusion beams, have been performed on rectangular sections 50x30xt mm. The thickness t varied from 1 to 2 mm. Cold rolled dual-phase and microalloyed steels as well as hot rolled microalloyed steels have beentested. The bending tests were carried out using three-point bending. The distance between the supports was 800 mm. During the test the load displacement plot was recorded. The maximum deformation was 150 mm.The maximum ultimate load, P max, as well as the absorbed energy wereFig 7 Maximum load P max vs. yield strength for bending testsBased on results from the axial crash tests and the bending tests we can draw some conclusions as to the gain in energy absorption at unchanged thicknessand reduced weight when using high strength steels instead of mild steels, table II [9].Table II: Gain in energy absorption and weight reduction when using high strength Docol DP steels instead of mild steelsDocol DP grade 600 800 1000 1200 1400Gain in energy absorption % 35 55 75 90 105Weight reduction % 25 30 35 40 45APPLICATIONSBased on the knowledge of how yield strength, plate thickness and overall geometry influence the structural properties and manufacturing properties of different constructions, high strength steels have already been successfully used in many applications.Hot rolled extra high strength steels are used for example in cranes, trucks and earth moving equipment. Figure 8 shows an application where Weldox 700 and Weldox 900 have been used for a mobile crane boom. Note that there are no welds on the flanges. The longitudinal weld situated in the neutral layer gives optimum structural performance in terms of fatigue.The use of Domex 690 XP grade is exemplified with a truck frame, figure 9. Note that rivets are used instead of welds in order to achieve the best fatigue performance.Another application for Domex 690 XP is a side reinforcing bar, which is a part of the Volvo side impact protection system, figure 10.Fig 8 Crane boom in Weldox 700 Fig 9 Truck frame inand Weldox 900 Domex 690 XPFig 10 Door intrusion beam in Fig 11 Back seat of the Volvo Domex 690 XP 850 Docol 600 DPFig 12 Bumper reinforcement Fig 13 Back seat top beam in in Docol 600 DL Dogal 500 YPFigure 10 shows a door beam where the use of Domex 690 XP combines high energy absorption with good cold formability and low weight.Figure 11 shows the back seat of the Volvo 850, where press-formed parts and tubes produced from Docol 600 DP are included to save weight.Figure 12 s hows a bumper reinforcement made of dual-phase grade Docol 600 DL where the low yield ratio gives the good formability to make the part.When corrosion protection is of great importance hot-dip galvanized microalloyed steel grades can be used. Figure 13 shows a transversal safety beam made of Dogal 500 YP which is used in the top of the back seat construction by the SAAB.REFERENCES[1]”Forming Handbook”SSAB Tunnplåt, 1997T[2] NILSSONWelding of DOMEX extra high strength cold forming steelSvetsen, special issue June 1995[3]LARSSON T BHandbook on welding of Oxelösund’s steelsSSAB Oxelösund, 1992[4] ”Sheet Steel Handbook”SSAB Tunnplåt, 1992[5] SPERLE J O AND NILSSON TThe Application of High Strength Steel for Fatigue LoadedStructuresProc. HSLA Steels Conf. on Processing, Properties andApplications, Beijing, 1992[6] SPERLE J OHigh Strength Steel for Light Weight Structures - Strength and PerformanceFatigueRoyal Institute of Technology, 1984[7] SPERLE J O AND LUNDH HStrength and Crush Resistance of Structural Members in High Strength Dual-Phase Steel SheetSc Journal of Metallurgy, 13(1984)6:343-351[8] SPERLE J O AND LUNDH HImproved Energy Absorption with High Strength Dual-PhaseSheetSteelProc. 12th Biennial Congress IDDRG, S Margherita, Italy,24 - 28 May, 1982[9] SPERLE J O AND OLSSON KHigh strength and Ultra High Strength Steels for WeightReduction in Structural and Safety Related ApplicationProc. ISATA Conf., Florence, 1996。

Ta含量对NiCoCrAlY涂层性能的影响陈建国; 张淑婷; 杜开平; 欧阳佩旋【期刊名称】《《热喷涂技术》》【年(卷),期】2019(000)003【总页数】6页(P38-43)【关键词】NiCoCrAlYTa; 涂层; 高温氧化; 抗热震性能【作者】陈建国; 张淑婷; 杜开平; 欧阳佩旋【作者单位】北京航天无人机系统工程研究所北京 100094; 北方工业大学机械与材料工程学院北京 100144; 北京矿冶科技集团有限公司北京 100160【正文语种】中文【中图分类】TG174.40 引言航空发动机的叶片、燃烧室、火焰筒等关键热端部件的高温氧化和腐蚀破坏是影响整机寿命、可靠性和运行安全性的主要因素，在热端部件表面制备MCrA1Y(M:Ni,Co)高温合金防护涂层，是解决这一问题最有效的方法[1-3]。

新一代航空发动机动力系统指标趋于极致化，如进气口温度超过1500℃，叶片使用寿命需超过300h等，MCrAlY高温合金涂层面临更高耐受温度、更长服役寿命和更高可靠性的挑战[4-6]。

为了进一步提高MCrAIY涂层的抗高温氧化及热腐蚀性能，人们进行了大量有益的探索，如对添加改性元素Re，Zr，Hf，Ta，Si等的MCrAIY 涂层体系进行了广泛和深入的研究[7,8]，其中添加Ta元素的NiCoCrAlYTa六组元合金涂层已用于航空发动机叶片的防护，显著提高了叶片的高温抗氧化性能[9-11]。

国内外针对含Ta的涂层主要围绕喷涂工艺、涂层抗氧化等性能开展了相关研究，如广东省新材料研究所毛杰[12]等人研究了不同热喷涂工艺对NiCoCrAlYTa涂层的显微结构和性能的影响，其结果表明，不同热喷涂工艺主要对涂层的孔隙率、氧含量、显微硬度产生影响，涂层物相组成未发生明显变化。

而Ta元素在NiCoCrAlY涂层中的分布、Ta含量在高温下对涂层抗氧化性能以及抗热震性能的影响等研究鲜有报道。

因此，本文设计并制备了不同Ta含量的NiCoCrAlYTa涂层，并对合金材料的物相、微观组织、高温抗氧化性能、抗热震性能等进行了实验研究，期望能为MCrA1Y涂层材料在不同环境下的应用提供参考。

Trans. Nonferrous Met. Soc. China 22(2012) 262−267Structure stability and mechanical properties of high-pressure die-cast Mg −Al −Ce −Y-based alloyZHANG Jing-huai 1, LIU Shu-juan 2, LENG Zhe 1, ZHANG Mi-lin 1, MENG Jian 3, WU Rui-zhi 11. Key Laboratory of Superlight Materials & Surface Technology of Ministry of Education,Harbin Engineering University, Harbin 150001, China;2. School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China;3. State Key Laboratory of Rare Earth Resources Utilization, Changchun Institute of Applied Chemistry,Chinese Academy of Sciences, Changchun 130022, ChinaReceived 28 February 2011; accepted 23 June 2011Abstract: With the aim to further improve the mechanical properties of Mg −Al −RE-based alloy, Mg −3.0Al −1.8Ce −0.3Y −0.2Mn alloy was prepared by high-pressure die-casting technique. The microstructure, thermal stability of intermetallic phases and mechanical properties were investigated. The results show that the alloy is composed of fine primary α-Mg dendrites and eutectic in the interdendritic regions. The intermetallic phases in eutectic are Al 11(Ce,Y)3 and Al 2(Ce,Y) with the former being the dominant one. The thermal stability of Al 11(Ce,Y)3 is conditioned. It is basically stable at temperature up to 200 °C within 800 h, while most of the Al 11(Ce,Y)3 intermetallics transform to Al 2(Ce,Y) at higher temperature of 450 °C for 800 h. The alloy exhibits remarkably improved strength both at room temperature and 200 °C, which is mainly attributed to the reinforcement of dendrite boundaries with Al 11(Ce,Y)3 intermetallics, small dendritic arm spacing effect as well as the solid solution strengthening with Y element. Key words: magnesium alloy; Mg −Al −Ce −Y alloy; Al 11RE 3; structure stability; mechanical properties1 IntroductionIn recent years, magnesium alloy in the form of high-pressure die-cast (HPDC) components has attracted much attention in automotive applications as advanced light material. Mg −Al-based alloys such as AZ91D and AM60B are used extensively in some non-critical parts [1]. However, these alloys are unsuitable for more critical components such as transmission and engine parts because of their poor mechanical properties at temperature above 125 °C [2, 3]. Further studies show that it is ascribed to the coarsening of β-Mg 17Al 12 phase in the eutectic region [4] and the discontinuous precipitate of lamellar Mg 17Al 12 from α-Mg matrix [5]. Moreover, a widely accepted view is that both diffusion controlled dislocation climbing and grain boundary sliding are the creep mechanisms in Mg −Al-based alloys [6]. Therefore, the design of alloys with good heatresistance should be based on the reinforcement of both the grain/dendrite boundaries and the α-Mg matrix.The Mg −Al −RE series alloys such as AE42 are the typical heat-resistant alloys designed for lightweight applications in the automotive industry [7]. However, there still appear inconsistencies in the previous reports as to the stability of the main strengthening phase Al 11RE 3 in Mg −Al −RE alloys. PETTERSON et al [8] (AE42 heat treated at 150, 200 and 250 °C for 100 h), HUANG et al [9] (AE42, 450 °C for 15 h), ZHU et al [5] (AE42, 200 °C for 2 weeks), DARGUSCH et al [10] (AE42+1%Sr, 200 °C for 2 weeks) and RZYCHO Ń et al [11] (AE44, 175 °C for 3000 h) reported that the intermetallic phase Al 11RE 3 has high thermal stability, and no decomposition is observed. In contrast, according to the work by POWELL et al [12] (AE42, 175 °C for 1000 h with and without stress) and our recent work [13] (AE44, 200 °C for 100 h under 70 MPa stress), Al 11RE 3 is unstable and partially decomposes to Al 2RE.Foundation item: Project (HEUCFR1128) supported by the Fundamental Research Funds for the Central Universities, China; Project (2010AA4BE031)supported by the Key Project of Science and Technology of Harbin City, China; Projects (20100471015, 20100471046) supported by the China Postdoctoral Science Foundation; Project (LBH-Z09217) supported by the Heilongjiang Postdoctorial Fund, ChinaCorresponding author: ZHANG Jing-huai; Tel: +86-451-82533026; E-mail: jinghuaizhang@ DOI: 10.1016/S1003-6326(11)61169-2ZHANG Jing-huai, et al/Trans. Nonferrous Met. Soc. China 22(2012) 262−267 263In this work, a new heat-resistant HPDC Mg alloy was designed. Relatively low Al content was used to improve the die castability, form high melting point intermetallics and try to avoid the formation of Mg17Al12. Ce with low solid solubility in Mg (0.74%, mass fraction) was added to form large amount of Al−Ce intermetallic particles to reinforce the grain/dendrite boundaries [14]; Y with high solubility in Mg (12.4%, mass fraction) was expected to strengthen the α-Mg matrix [14]. The microstructure, thermal stability of intermetallic and mechanical properties at room temperature and 200 °C of HPDC Mg−Al−Ce−Y-based alloy were investigated.2 ExperimentalThe chemical composition of the experimental alloy was Mg−3.0Al−1.8Ce−0.3Y−0.2Mn (ACY320). The reference alloy prepared under the same condition was Mg−3.3Al−0.2Mn (AM30). Commercial pure Mg and Al were used. Ce, Y and Mn were added in the form of Mg−20%Ce, Mg−20%Y and Al−10%Mn master alloys (mass fraction). Specimens were die cast using a 280 t clamping force cold chamber die-cast machine. About 20 kg raw materials were melted in a mild steel crucible. Pure argon was used as protective gas and refined gas. The molten metal was hand-ladled into the casting machine and the melt temperature prior to casting was about 700 °C. The die was equipped with an oil heating/cooling system and the temperature of the oil heater was set to 220 °C. The chemical compositions of the castings were determined by inductively coupled plasma atomic emission spectrometer.The tensile samples were 70 mm in gauge length and 6 mm in gauge diameter, as shown in Fig. 1. Tensile tests were performed using Instron 5869 tensile testing machine at a strain rate of 1.1×10−3 s−1. The experimental result in the study was the average value of at least four measured specimens. Metallographic sample was cut from the middle segment of the tensile bar. The microstructures and intermetallic phases were characterized by scanning electron microscope (SEM)Fig. 1 Photo of HPDC tensile test bars obtained from ACY320 alloy equipped with an energy dispersive X-ray spectrometer (EDS) and X-ray diffractometer (XRD).3 Results and discussion3.1 MicrostructureIn order to understand the role of Ce and Y additions in the Mg−3Al-based alloy, the microstructure of HPDC AM30 alloy is observed, as shown in Fig. 2(a). It reveals that the AM30 alloy is composed of primary α-Mg dendrites surrounded by interdendritic eutectic. A spot of β-Mg17Al12 intermetallics disperses in the interdendritic regions. The average dendritic arm spacing (DAS) is about 17 μm. The remarkable changes in the microstructure can be observed with the addition of Ce and Y, as shown in Fig. 2(b). The primary α-Mg dendrites in HPDC ACY320 alloy tend to be equiaxed and the average DAS is reduced to 9 μm. More important, the amount of intermetallic compounds in the interdendritic regions is much higher than that in AM30 alloy with the similar Al content.3.2 Intermetallics and their thermal stabilityThe XRD result of the HPDC ACY320 alloy is illustrated in Fig. 3(a). It is known that Mg−Al−Zn (AZ) and Mg−Al−Mn (AM) alloys are mainly composed of α-Mg and β-Mg17Al12 phases [15], the diffraction peaks of β-Mg17Al12 are not emerged due to the addition of Ce and Y. The main secondary phases in ACY320 alloy are Al11(Ce,Y)3 and Al2(Ce,Y), while the diffraction peak of Al11(Ce,Y)3 is much more intense than that of Al2(Ce,Y), which suggests that the former is the dominant one.The magnified SEM images characterizing the secondary phases are shown in Figs. 2(c) and (d). The acicular intermetallics with length of 1−3 μm arrange in a row then the rows form layers roughly, which exhibits outstanding morphology and distribution of the intermetallics. Besides, a few polyhedral intermetallics with size of 1−5 μm can be observed by SEM observations. EDS analyses were used to identify these intermetallics. Figures 2(e) and (f) show the EDS spectra detected from acicular intermetallics and polyhedral intermetallic, respectively. Combined with the XRD result, the acicular intermetallic is identified as Al11(Ce,Y)3 and the polyhedral one corresponds to Al2(Ce,Y). It is worthwhile to note that Al11(Ce,Y)3 has higher content of Ce than Y, while Y content is much higher than Ce in Al2(Ce,Y).To study the thermal stability of Al11(Ce,Y)3 intermetallic, some samples were aged at 200 and 450 °C for 800 h, respectively. The microstructure of ACY320 alloy after heat treatment is shown in Fig. 4. There is no obvious evidence of decomposition of the intermetallics in 200 °C annealed sample, except that a few particlesZHANG Jing-huai, et al/Trans. Nonferrous Met. Soc. China 22(2012) 262−267264Fig. 2 SEM images and EDS analyses of HPDC alloys: (a) SEM images of AM30 alloy; (b, c, d) SEM images of HPDC ACY320 alloy; (e) EDS analyses of acicular intermetallics at point A ; (f) EDS analyses of polyhedral intermetallic at point BFig. 3 XRD patterns of HPDC ACY320 alloys before aging (a), after aging at 200 °C for 800 h (b) and after aging at 450 °C for 800 h (c)show certain coarsening (see Figs. 4(a)−(c)). The XRD patterns also show incognizable changes before and after 200 °C aging by comparing Figs. 3(a) and (b). However, the conspicuous change of microstructure could be observed after age treatment at higher temperature of 450 °C (Figs. 4(d)−(f)). It reveals that most of the acicular intermetallics disappear and give place to fine quadrate-like particles with size of 100−400 nm in interdendritic regions. The XRD pattern illustrated in Fig. 3(c) also changes obviously after 450 °C aging, namely, the intensity of Al 11(Ce,Y)3 peaks decreases and that of Al 2(Ce,Y) peaks increases obviously. In addition, EDS in SEM mode also indicates the Al: (Ce,Y) atom ratio of these small particles is close to 2:1, not 11:3. Therefore, the present study shows a clear evidence ofZHANG Jing-huai, et al/Trans. Nonferrous Met. Soc. China 22(2012) 262−267 265Fig. 4 SEM images of HPDC ACY320 after ageing at 200 °C (a, b, c) and 450 °C for 800 h (d, e, f)the phase transition according to the reaction Al 11(Ce,Y)3 → 3Al 2(Ce, Y) + 5Al [12].The observations reported here suggest that there is a limit to the thermal stability of Al 11RE 3. Up to now, the thermal stability of the main strengthening phase Al 11RE 3 in Mg −Al −RE alloys is still a matter of debate [6, 9−14]. POWELL et al [12] investigated the microstructural stability of die-cast AE42 (Mg −4Al −2RE) alloys which were individually creep tested for 1000 h at 22, 100, 125, 150 and 175 °C. It was reported that the lamellar/acicular phase Al 11RE 3, which dominates the interdendritic microstructure of the alloy, partly decomposes into Al 2RE and Al (forming Mg 17Al 12) at temperature above 150 °C (i.e. 175 °C), and the sharp decrease in the creep resistance is attributed to the reduced presence of the lamellar/acicular Al 11RE 3 and the appearance of Mg 17Al 12. In addition, it was also pointed out that the stress is not a contributing factor to Al 11RE 3 stability. However, ZHU et al [5] reported that intermetallic phaseAl 11RE 3 in die-cast AE42 has high thermal stability with no decomposition observed at temperature up to 200 °C for 336 h, meanwhile, the continuous precipitation of Mg 17Al 12 due to the supersaturation of Al solute was observed in the Mg matrix, which was considered to be responsible for the deterioration in creep resistance at temperatures above 150 °C. In the present work, as for the alloy Mg −3.0Al −1.8Ce −0.3Y −0.2Mn after severe aging treatment at 200 °C for 800 h, neither obvious decomposition of Al 11RE 3 (i.e. Al 11(Ce,Y)3) nor the formation of Mg 17Al 12 is observed. It is considered that following aspects are related to the stability of Al 11RE 3 and the formation of Mg 17Al 12. First, the harsh degree of aging treatment containing aging temperature and time is an important factor for the composition of Al 11RE 3. This may be responsible for the different observation results by POWELL et al (175 °C for 1000 h) and ZHU et al (200 °C for 336 h) in AE42 alloy as well as ACY320 alloy in this study (200 °C for 800 h and 450 °C forZHANG Jing-huai, et al/Trans. Nonferrous Met. Soc. China 22(2012) 262−267 266800 h) at different aging temperatures. Second, the difference of RE components also affects the stability of Al11RE3 [13], which is a factor to explain the difference between Al11RE3 in AE42 and Al11(Ce, Y)3 in ACY320 alloy. Last, the lower Al content in ACY320 (3%) compared with that in AE42 (4%) causes little Al sequestered as soluted in the Mg matrix, which is responsible for no discernible precipitation of Mg17Al12 after aging in ACY320 alloy. The absence of DSC analysis to study phase transition challenges further work.3.3 Mechanical propertiesThe representative tensile stress—strain curves of HPDC ACY320 and AM30 alloys at room temperature and 200 °C are shown in Fig. 5. The tensile properties including ultimate tensile strength, tensile yield strength and elongation to failure are listed in Table 1. The strength increases dramatically by 45−65 MPa both at room temperature and 200 °C, while the elongation still keeps a high level with the addition of Ce and Y to AM30 alloy. The following aspects are considered to be related to the improved strength. The first and also the most important aspect is the formation of large amountFig. 5 Typical tensile stress—strain curves of HPDC alloys at room temperature (a) and 200 °C (b) of Al11(Ce,Y)3 intermetallics which provide considerable reinforcement of dendrite boundaries. Second, since the DAS is finer for the Mg−3Al-based alloys containing Ce and Y, the fine DAS effect can contribute to the observed increase in strength. Another factor is the strengtheningof the α-Mg matrix by solid solution with rare earth elements especially Y. Generally, the ductility is low for the alloy containing large amount of intermetallic particles [16]. However, the elongation of HPDC ACY320 alloy with high volume fraction of intermetallics still keeps a high level. It may be related tothe fine morphology and arrangement of Al11(Ce,Y)3 intermetallics.Table 1 Tensile and compressive properties of HPDC alloys at room temperature and 200 °CRoom temperatureAlloy Tensile yieldstrength/MPaUltimate tensilestrength/MPaElongation/%ACY320 158 255 10 AM30 116 191 9200 °CAlloy Tensile yieldstrength/MPaUltimate tensilestrength/MPaElongation/%ACY320 103 120 22 AM30 60 72 18 4 Conclusions1) With the addition of 1.8% Ce and 0.3% Y to Mg−3%Al-based alloy, the primary Mg dendrites are refined, the intermetallic phase Mg17Al12 is completely suppressed and substituted by Al11(Ce,Y)3 and Al2(Ce,Y) with the former being the dominant one at the interdendritic regions.2) Al11(Ce,Y)3 intermetallics are basically stable at temperature up to 200 °C within 800 h, while most of theAl11(Ce,Y)3 transform to Al2(Ce,Y) at higher temperatureof 450 °C for 800 h. This suggests that the thermal stability of Al11RE3 is conditioned.3) The high-pressure die-cast Mg−3.0Al−1.8Ce−0.3Y−0.2Mn alloy exhibits significantly improved strength at room temperature and 200 °C, which is the results of the reinforcement of dendrite boundaries withAl11(Ce,Y)3 intermetallics, fine dendritic arm spacing effect as well as the solid solution strengthening with Y element.References[1]KULEKEI M K. Magnesium and its alloys applications inautomotive industry [J]. Int J Adv Manuf Tech, 2008, 39(9−10):851−865.ZHANG Jing-huai, et al/Trans. Nonferrous Met. Soc. China 22(2012) 262−267 267[2]WANG Jian-li, PENG Qiu-ming, WU Yao-min, WANG Li-min.Microstructure and mechanical properties of Mg−6Al−4RE−0.4Mnalloy [J]. Transactions of Nonferrous Metals Society of China, 2006,16: s1703−s1707.[3]TONG Guo-dong, LIU Hai-feng, LIU Yao-hui. Effect of rare earthadditions on microstructure and mechanical properties of AZ91magnesium alloys [J]. Transactions of Nonferrous Metals Society ofChina, 2010, 20: s336−s340.[4]BAKKE P, WESTENGEN H. Die casting for highperformance-focus on alloy development [J]. Adv Eng Mater, 2003,5(12): 879−885.[5]ZHU S M, GIBSON M A, NIE J F, EASTON M A, ABBOTT T B.Microstructure analysis of the creep resistance of die-castMg−4Al−2RE alloy [J]. Scripta Mater, 2008, 58(6): 477−480.[6]LUO A A. Recent magnesium alloy development for elevatedtemperature application [J]. Int Mater Rev, 2004, 49(1): 13−30.[7]WANG J, LIAO R, WANG L, WU Y, CAO Z, WANG L.Investigations of the properties of Mg−5Al−0.3Mn−x Ce (x=0−3,wt.%) alloys [J]. J Alloys Compd, 2009, 477(1−2): 341−345.[8]PETTERSEN G, WESTENGEN H, HØIER R, LOHNE O.Microstructure of a pressure die cast magnesium-4wt.% aluminiumalloy modified with rare earth additions [J]. Mater Sci Eng A, 1996,207(1): 115−120.[9]HUANG Y D, DIERINGA H, HORT N, MAIER P, KAINER K U,LIU Y L. Evolution of microstructure and hardness of AE42 alloyafter heat treatments [J]. J Alloys Compd, 2008, 463(1−2): 238−245. [10]DARGUSCH M S, ZHU S M, NIE J F, DUNLOP G L.Microstructural analysis of the improved creep resistance of adie-cast magnesium-aluminium-rare earth alloy by strontium additions [J]. Scripta Mater, 2009, 60(2): 116−119.[11]RZYCHON T, KIELBUS A, CWAJNA J, MIZERA J.Microstructural stability and creep properties of die casting Mg−4Al−4RE magnesium alloy [J]. Mater Charact, 2009, 60(10):1107−1113.[12]POWELL B R, REZHETS V, BALOGH M P, WALDO R A.Microstructure and creep behavior in AE42 magnesium die-castingalloy [J]. JOM, 2002, 54(8): 34−38.[13]ZHANG Jing-huai, YU Peng, LIU Ke, FANG Da-qing, TANGDing-xiang, MENG Jian. Effect of substituting cerium-rich mischmetal with lanthanum on microstructure and mechanicalproperties of die-cast Mg−Al−RE alloys [J]. Mater Design, 2009,30(7): 2372−2378.[14]ZHANG Jing-huai, LIU H F, SUN W, LU H Y, TANG D X, MENG J.Influence of structure and ionic radius on solubility limit in theMg−RE systems [J]. Mater Sci Forum, 2007, 561−565: 143−146. [15]SU Gui-hua, ZHANG Liang, CHENG Li-ren, LIU Yong-bing, CAOZhan-yi. Microstructure and mechanical properties of Mg−6Al−0.3Mn−x Y alloys prepared by casting and hot rolling [J].Transactions of Nonferrous Metals Society of China, 2010, 20(3):383−389.[16]BAE D H, KIM S H, KIM D H, KIM W T. Deformation behavior ofMg−Zn−Y alloys reinforced by icosahedral quasicrystalline particles[J]. Acta Mater, 2002, 50(9): 2343−2356.Mg−Al−Ce−Y基压铸合金的微观结构稳定性和力学性能 张景怀1, 刘淑娟2, 冷哲1, 张密林1, 孟健3, 巫瑞智11. 哈尔滨工程大学超轻材料与表面技术教育部重点实验室，哈尔滨 150001；2. 哈尔滨工业大学材料科学与工程学院，哈尔滨 150001；3. 中国科学院长春应用化学研究所稀土资源利用国家重点实验室，长春 130022摘 要：为进一步提高Mg−Al−RE基合金的力学性能，采用高压压铸技术制备Mg−3.0Al−1.8Ce−0.3Y−0.2Mn合金，并研究其微观组织、金属间相的热稳定性和合金的力学性能。

北科大考博辅导班：2019北京科技大学材料科学与工程考博难度解析及经验分享根据教育部学位与研究生教育发展中心最新公布的第四轮学科评估结果可知，在科教评价网版2017-2018材料科学与工程专业大学排名中，材料科学与工程专业排名第一的是清华大学，排名第二的是北京航空航天大学，排名第三的是武汉理工大学。

作为北京科技大学实施国家“211工程”和“985工程”的重点学科，新金属国家重点实验室的材料科学与工程一级学科在历次全国学科评估中均名列第四。

下面是启道考博辅导班整理的关于北京科技大学材料科学与工程考博相关内容。

一、专业介绍材料科学与工程，在国务院学位委员会学科评议组制定和颁布的《授予博士、硕士学位和培养研究生的学科、专业目录》中，材料科学与工程属于工学学科门类之中的其中一个一级学科，下设3个二级学科，分别是:材料物理与化学、材料学、材料加工工程。

材料科学与工程专业是研究材料成分、结构、加工工艺与其性能和应用的学科。

在现代科学技术中，材料科学是国民经济发展的三大支柱之一。

主要专业方向有金属材料、无机非金属材料、高分子材料、耐磨材料、表面强化、材料加工工程等等。

北京科技大学新金属国家重点实验室的材料科学与工程在博士招生方面，划分为60个研究方向080500 ★材料科学与工程研究方向：01 新型高性能汽车及船舶用铝合金的研究与开发02 极端性能材料的力学理论研究02 铝、镁等轻合金先进制备加工全程工艺优化研究03 可降解生物医用金属材料研究与开发04 金属燃烧机理与抗燃烧合金研究开发05 结构-功能金属间化合物06 难变形材料的强加工和组织精确控制07 新型金属间化合物多孔材料08 高熵高温合金09 非晶软磁合金10 材料基因工程11 金属智能材料12 磁性功能材料13 功能复合材料14 非晶合金的玻璃转变15 外场作用金属塑性加工16 轻合金的耐候性17 高熵合金和陶瓷18 超弹性材料19 塑性流动20 新型钴基与镍基单晶高温合金的高温力学行为21 高温合金热端部件服役损伤评价方法22 高温结构材料的材料基因工程研究方法23 高熵合金24 高性能钢铁材料25 非晶态合金26 功能复合材料27 磁致伸缩材料28 储氢材料29 全固态锂离子电池材料30 先进锆合金及钛合金31 核电关键部件材料服役性能及评价32特殊环境用高性能不锈钢结构材料33 高强韧汽车结构件铝合金34 新一代装甲板/船用铅合金开发和应用35 金属连铸工艺过程模拟和优化36 高强韧航空用铝合金37 新一代高铁/磁悬浮轨道交通用铝合金38 高性能形状记忆合金39 金属智能材料40 磁场、应力场作用下的马氏体相变及多功能特性41 纳米准晶及应用42 高性能高熵合金及微观机理43 电子显微学方法44 金属材料微观力学行为研究45 工程材料部件三维多尺度应力测量与损伤评估46 新型形状记忆合金相变行为与功能47 导热复合材料48 电子封装材料49 航空航天用难熔金属硅化物、钛铝超高温结构材料50 耐液态金属腐蚀材料与多孔材料51 可控电弧丝材熔覆、堆焊与3D打印；热喷涂52 兵器材料失效特征与机理53 兵器材料的设计与制备54 极端工况材料燃烧特征与机理55 高熵合金56 非晶态合金57 金属材料强韧化58 三维原子探针结构表征59 等离子体表面工程60 金属燃烧考试科目：①1001 外语水平考核②2001 专业水平考核③3001 综合素质考核二、考试内容北京科技大学材料科学与工程专业博士研究生招生考试的考核阶段，其中，综合考核内容为:成立学科专家组，根据本学科专业前沿发展趋势和培养要求，采用笔试加面试（多种）方式对申请人的综合应用知识能力、外语应用能力、本学科专业前沿知识及最新研究动态掌握情况等方面进行考核，重点考核申请人是否具有研究潜质、创新精神和创新能力。

A12时效温度对HSLA-100高强船体钢组织性能的影响罗小兵苏航杨才福柴锋钢铁研究总院结构材料研究所北京 100081摘要：采用固溶+时效的热处理方法研究了时效温度对HSLA-100含铜高强船体钢组织性能的影响。

结果表明，试验钢在450℃处出现强度峰值，这是由大量纳米级的Cu析出物（<5nm）和少量Nb(C,N)第二相粒子的析出强化造成的。

过时效状态下，Cu析出粒子尺寸显著增大（10 nm~30 nm），其形状由球状变为杆状或短棒状，晶体结构也由bcc转变为fcc结构，并与基体失去共格关系，沉淀强化作用也逐渐减弱。

时效过程中基体软化和第二相粒子沉淀强化的共同作用决定了含铜高强船体钢的性能变化规律。

关键词：时效温度 HSLA-100 Cu 沉淀强化船体钢Effect of aging temperature on microstructure and properties of HSLA-100 highstrength ship hull steelsLUO Xiaobing, SU Hang , YANG Caifu, CHAI FengCentral Iron and Steel Research Institute, Institute for structural materials, Beijing 100081, China Abstract：Processing of quenching and aging was applied in this paper to research the effect of aging temperature on microstructure and properties of HSLA-100 copper-bearing high strength ship-hull steels. The results indicated that t he strength of tested steels were peaked while aging at 450℃ which attributed to the large amount of fine Cu particles( less than 5nm)and a small number of Nb(C,N) precipitates. The size of Cu particles happened to coarsen(10 nm~30 nm)in the condition of over aging, and it grew to rod-like from spherical in the particle shape, and lost the relationship of coherency to matrix , finally its precipitation strengthening is weakened. In addition, competition between the soften of matrix and the strengthen by second phase determined the aging regularity of copper-bearing high strength ship-hull steels.Keywords：Aging Temperature HSLA-100 Cu Precipitation Strengthening Ship-Hull steels0 前言随着国内外对铜在钢中作用研究的不断深入，Cu的沉淀强化技术被人们广泛应用于船舶、桥梁、汽车、石油化工、压力容器等领域。