Ti_3Al-Nb合金的有序转变

研究了Ti_3Al-Nb合金在高温下的有序化,冷却过程高温β相转变及时效过程亚稳定β相分解的行为,结果指出,在1060℃固溶处理时,合金形成初生α_2和β高温有序相;在固溶处理后的冷却过程中,合金发生β→α_2+ω型转变;在700℃时效过程中,合金发生(β+ω型)亚稳→(α_2+β)稳定分解。     

Nb对Ti3Al电子结构和韧化的影响

用离散变分Xa原子簇方法计算了Ti_3Al及加入Nb后的电子结构对键级及其组成的分析表明:由于Nb的加入改变了合金的电子结构,降低了键级中p—p作用,提高了d—d作用在键级Bo中的比例,有利于位错滑移的进行,对Ti_3Al具有一定的韧化作用对Nb占据Al及Ti位置时Bo的变化分析表明:由于Nb代Ti位置时Bo有较大的提高,使系统更稳定。因而,在Ti_3Al中Nb应占据Ti的位置.     

Ti_3Al基合金超塑形变的微观观察

Ｔｉ－２５Ａｌ－１０Ｎｂ－３Ｖ－１Ｍｏ（ａｔ．－％）合金在９００－９８０℃温度范围和１×１０~（－３）Ｓ~（－１）拉伸速率下显示了良好的超塑性能，δ＝３８２％．其超塑形变受控于晶界滑动（主要为α_２／α_２晶界滑动），并协调以扩散、位错、位错环和层错机制．扩散协调机制表现为螺旋位错和割阶的攀移，位错协调制主要为的位错的滑移．位错环主要为的切变型位错环，并伴有少量的扩散切变型位错环．     

Fe3Al合金B2有序化过程的场离子显微镜观察

对不同有序度下的Ｂ２结构Ｆｅ_３Ａｌ进行了场离子显微镜（ＦＩＭ）研究．不论是否达到最大Ｂ２有序度，ＦＩＭ像的总体规则程度均很差，难以由常规方法得到有序度的信息．但是，ＦＩＭ像中的局部区域，也即〈１００〉极的场蒸发过程却提供了Ｂ２有序度的信息，通过对其连续观察发现，Ｆｅ_３Ａｌ的Ｂ２有序化进程在纳米尺度范围是不均匀的．从〈１２０〉极上得到的结果与〈１００〉极一致．这种一致性再一次证实了“Ａｌ成像，Ｆｅ不可见”的观点是正确的．     

Fe3Al合金中D03有序化过程的场离子显微镜研究

经５００℃保温５天有序化处理得到的Ｄ０３结构Ｆｅ３Ａｌ，其场离子显微镜（ＦＩＭ）像具有十分发达的环结构，但〈１１１〉极环结构的清晰程度明显低于〈１００〉极．连续观察可以发现，〈１００〉极的场蒸发过程简洁，而〈１１１〉极较复杂．分析表明，经这种有序化处理后，Ｄ０３结构下的ＳＩ型有序已趋于完成，而ＳＩＩ型有序尚未完成．在同一温度下，即使延长保温时间，〈１１１〉极衬度也未有明显好转，表明在５００℃下处理得到的Ｄ０３有序结构并不完整．     

Ti3Al基合金的拉伸形变和断裂

测试了三种显微组织Ｔｉ３Ａｌ基合金的室、高温拉伸性能；并用ＳＥＭ和ＴＥＭ详细观察样品的形变和断裂特征，结果发现，材料的力学性能与断口和位错组态的变化密切相关，随实验温度升高，强度降低，延性增加；随固溶温度提高，强度增加，延性降低，三种组织室温拉伸均为解理断裂，温度呈现解理与沿晶混合断裂。     

Cu-Zn-Al合金中马氏体的有序化对形状记忆效应的影响

研究了Cu-Zn-Al合金分别经水淬、分级淬火和淬火加时效处理后,马氏体的有序化程度及其和形状记忆效应(SME)之间的关系.有序化程度用一些特定马氏体线对的面间距差值△d来表征,线对指数应满足下式:(h_1~2-h_2~2)/3=(k_2~2-k_1~2)/n(对9R马氏体n=1,对18R马氏体N=4).分级淬火得到M18R马氏体,其△d值随分级等温时间而增大,与形状恢复能力η的提高一致.水淬得到M9R马氏体,刚淬火状态有相当大的△d和良好的SME,但室温停留使△d和η均下降,TEM点阵条纹象证实这是淬火过饱和空位在(001)_M基面聚集、降低有序程度的结果.淬火后高温时效(180℃)或过高的分级温度都会使△d和η下降,这与α相析出以及可能发生的溶质原子偏聚有关,都会降低有序程度.     

EFFECT OF MARTENSITE ORDERING ON SME IN A Cu-Zn-Al ALLOY

The correlation between the shape memory effect(SME)and the ordering degree inmartensite formed through various heat-treatment processes,e.g.ice water quenching,step-quenching and aging etc.,has been studied in a Cu-26Zn-4Al alloy.The martensite or-dering degree is estimated by △d,the spacing difference of some pairs of diffracting planeswith indices satisfying a relation of(h_1~2-h_2~2)/3=(k_2~2-k_1~2)/n(n=1 for 9R martensite,n=4for 18R martensite).M 18R martensite is obtained from step-quenching,in which the valueof △d increases with the holding duration of step-quenching,and the shape recoveryrate η increases synchronouslly.9R martensite is obtained from direct water-quenching,thevalue of △d is quite large and SME is also good at just quenching state.But both △dand η decrease continuously with aging time at room temperature.This stabilization phe-nomenon of martensite is explained by the observation of TEM lattice fringe image,and itmay be attributed to the clustering of quenched-in supersaturated vacancies at(001)_M close-packed plane in martensite and decreasing the ordering degree.A reduction in△d and η occuring in the specimens on step-quenching or aging at higher temperature,which may be related to the precipitation of the α-phase and the enrichment of solute atoms,decreases the ordering degree.     

Ti_3SiC_2弥散强化Cu:一种新的弥散强化铜合金

选用具有高导电、高导热性能的新型陶瓷Ti3SiC2做为弥散强化相,通过与Cu粉末高能球磨混合后,热压成一种新型弥散强化Cu材料机械性能测试表明,随着Ti3SiC2体积分数的提高,弥散强化,Cu的屈服强度和维氏硬度线性上升分析表明Ti3SiC2相的晶粒细化和位错塞积是主要强化机制,当颗粒粗化和团聚后Ti3SiC2的强化效果将明显减弱     

FRACTURE MECHANISM IN Ti_3Al Si Nb ALLOYS

ＦＲＡＣＴＵＲＥＭＥＣＨＡＮＩＳＭＩＮＴｉ_３Ａｌ＋Ｓｉ＋ＮｂＡＬＬＯＹＳＷＵＪｉａｎｓｈｅｎｇ；ＺＨＡＮＧＬａｎｔｉｎｇ；ＱＩＵＧｕｏｈｕａ（ＤｅｐａｒｔｍｅｎｔｏｆＭａｔｅｒｉａｌｓＳｃｉｅｎｃｅ，ＳｈａｎｇｈａｉＪｉａｏＴｏｎｇＵｎｉｖｅｒｓｉ?..     

EFFECT OF HYDROGENATION ON THE MICROSTRRUCTURE OFTi-24Al-14Nb-3V-0.5Mo ALLOY

1.IntroductionTisAlbasedintermetallics,aswellas0thertitaniumaluminidesarecurrentlyreceivingmuchattellti0nbecause0ftheirhighspecificstrengthatelevatedtemperatureandpo-telltialutilizationasadvancedaerospacematerialsl1'2l-Howevertheproblemsassociatedwithlowtemperaturebrittlenessinthistype0falloyremainsamajorobstacletoitsap-plication.Certaintechniquessuchasthermo-mechanicalprocessingd]andthermochemicalprocessing[']havebeenemployedtoalterthemicr0structureoftheseall0yswithaimedatimprovingtheirmechan…     

Ti_3AlC_2与Cu合金的电弧焊接

采用无焊料电弧焊方法对Ti_3AlC_2陶瓷与Cu(Mg)合金进行焊接.观察分析了接头组织结构和物相组成,测试了焊接试样的弯曲强度.结果表明,Ti_3AlC_2陶瓷和Cu(Mg)合金之间具有良好的可焊接性.在适当的焊接工艺下,接头具有典型显微结构:在靠近Cu(Mg)合金的区域,自生成的细小TiCx颗粒均匀弥散在Cu(Ti, Al, Mg)合金网络内;在靠近Ti_3AlC_2陶瓷的区域,形成TiC_x相与Cu(Ti, Al, Mg)合金相交替层叠的特殊结构.焊接试样的断裂发生在Ti_3AlC_2陶瓷部分,表明接头的抗弯强度高于被焊接的Ti_3AlC_2陶瓷材料.     

燃烧合成Ti_3AlC_2及其热稳定性

采用燃烧合成技术,通过改变Ti、Al和C 3种粉末的比例制备出高纯度的Ti_3AlC_2块体材料,并对其在氩气中的高温热稳定性进行了研究.X射线衍射(XRD)表明合成产物除了含有Ti_3AlC_2外,还含有少量TiC和Ti-Al金属间化合物,经k值法计算得Ti_3AlC_2最高含量为96.7%.耦合等离子-原子发射光谱(ICP-AES)结果表明最高纯度的合成产物中Ti、Al质量分数分别为74.2%和13.7%,与Ti_3AlC_2中Ti和Al含量十分接近.利用SEM对燃烧产物断口进行了观察,发现明显的层片状结构.热重-差热(TG-DTA)结果表明燃烧合成的高纯Ti_3AlC_2在加热过程中没有明显的热效应,说明合成的产物处于近似平衡状态.Ti_3AlC_2的分解温度在1370 ℃左右,同时由于氧化作用而导致试样质量略有增加.     

含硼的Cu—Zn—Al合金中母相晶粒度和有序度对Ms的影响

研究了母相平均晶粒尺寸和有序度对Cu-25.62Zn-3.97Al-0.0018B(wt-％)形状记忆合金热弹性马氏体相变点的影响。从相变热力学出发,得到马氏体相变点和晶粒尺寸的平方根的倒数成线性关系,并且随晶粒尺寸增大,马氏体相变点升高,与电阻法测得的结果符合很好。运用Landau理论,得到马氏体相变点和母相有序度的定量关系式,与X光衍射和电阻法试验的结果符合较好。求得试验用合金母相DO_3有序化的激活能约为46kJ/mol。     

母相晶粒度和有序度对含硼Cu—Zn—Al合金形状记忆效应的影响

本文研究了母相晶粒度和有序度对Cu-25.62Zn-3.97Al-0.0018B(wt-％)记忆合金形状回复的影响。试样的回复量通过圆弧弯曲法测定。建立了回复率与有序度、晶粒尺寸、晶界影响区宽度、试样变形时的应力和临界切应力之间的数学关系。形状记忆效应随晶粒尺寸变化出现极大值,随有序参数增大而线性上升,与试验结果相符。     

INFLUENCE OF GRAIN SIZE AND ORDERING OF PARENT PHASE ON M_s IN A CuZnAl ALLOY CONTAINING BORON

The effect of grain size and ordering of the parent phase on the critical points of thermoelasticmartensitic transformation in Cu-25.62 Zn-3.97 Al-0.0018 B(wt-%)shape memory alloyhas been investigated.Based on the thermodynamics of phase transformation,a linear rela-tionship between the starting temperature of martensitic transformation and the reciprocal ofthe square root of grain size is obtained,i.e.M_s temperature rises with increasing grain size.It shows a good agreement with the results of electric resistance measurement.Applying theLandau's theory,a quantitative relationship between M_s and the ordering parameter of theparent phase is set up,which is well confirmed by the results of X-ray diffraction and electricresistance measurement.The activation energy of the ordering process in the parent phase ofthe alloy is calculated to be 46 kJ/mol.     

INFLUENCE OF GRAIN SIZE AND ORDERING DEGREE OF PARENT PHASE ON SME IN A CuZnAl ALLOY CONTAINING BORON

The influence of grain size and ordering degree of the parent phase on the shape memory re-covery in a Cu-25.62Zn-3.97Al-0.0018B(wt-%)memory alloy is investigated.Amathematical relationship is set up between the recovery ratio and ordering degree,probabili-ty of atoms at their ordered sites,grain size,the thickness of the grain boundary affected re-gions,the stress during deformation,as well as the critical shear stress.Shape memory effectreaches a maximum with varying grain size and increases linearly with increasing orderingparameter,which agrees well with experimental results.     

ADVANCE IN Ti_3 Al AND TiAl INTERMETALLICS RESEARCH IN CISRI

ＡＤＶＡＮＣＥＩＮＴｉ_３ＡｌＡＮＤＴｉＡｌＩＮＴＥＲＭＥＴＡＬＬＩＣＳＲＥＳＥＡＲＣＨＩＮＣＩＳＲＩＺＨＯＮＧＺｅｎｇｙｏｎｇ；ＺＯＵＤｕｎｘｕ；ＬＩＳｈｉｑｉｏｎｇ（ＣｅｎｔｒａｌＩｒｏｎａｎｄＳｔｅｅｌＲｅｓｅａｒｃｈＩｎｓｔｉｔｕｔｅ，Ｂｅｉ?..     

OXIDATION RESISTANCE AND MECHANICAL PROPERTIES OF Ti_3Al-Nb-Mo-Si ALLOYS

ＯＸＩＤＡＴＩＯＮＲＥＳＩＳＴＡＮＣＥＡＮＤＭＥＣＨＡＮＩＣＡＬＰＲＯＰＥＲＴＩＥＳＯＦＴｉ_３Ａｌ－Ｎｂ－Ｍｏ－ＳｉＡＬＬＯＹＳＳＵＮＹｕｆｅｎｇ；ＣＡＯＣｈｕｎｘｉａｏ；ＣＡＯＪｉｎｇｘｉａ；ＹＡＮＭｉｎｇｇａｏ（ＢｅｉｊｉｎｇＩｎｓｔｉｔｕｔｅ?..     

放电等离子烧结热处理合成Ti_3SiC_2粉体

采用机械合金化合成TiC和Ti_3SiC_2混合粉体,用放电等离子烧结(SPS)系统对该粉体进行热处理,以合成高纯Ti_3SiC_2粉体.结果表明,采用SPS无压热处理可以促进机械合金化粉体在较低温度转变成高纯Ti_3SiC_2粉体材料.随热处理温度(700～1000℃)的升高,产物中Ti_3SiC_2的含量相应增加,当热处理温度为900 1000℃时,产物中Ti_3SiC_2纯度可达98wt%.