Ni_(47)Ti_(44)Nb_9合金的相变滞后和应变马氏体的稳定性SCIEI

用不同温度下的拉伸试验、电阻法测量和透射电镜分析系统地研究了Ni_(47)Ti_(44)Nb_9合金的相变滞后及其影响因素,探讨了应变马氏体的稳定性。结果表明,存在一个特征形变温度和形变量范围,在这个范围内形变时,可以得到宽的相变滞后和高的应变恢复率。不规则的孪晶马氏体和含有位错亚结构的马氏体,以及与β-Nb质点相交截的马氏体都具有较高的稳定性。     

Cu-Zn-Al合金热弹性马氏体稳定化机理的探讨SCIEI

本文研究了快速凝固Cu-Zn-Al合金热弹性马氏体稳定化的机理,认为该合金马氏体稳定化实际上是一个原子组态由有序向无序、马氏体结构由M18R向b/a=1/3^(1/2)的N9R转变的过程,这一过程是由马氏体固有的分解趋势所决定的。     

Cu-Zn-Al合金马氏体稳定化与母相有序态SCIEI

采用X射线衍射和内耗测量研究了Cu-Zn-Al合金不同热处理条件对马氏体相变和母相有序态的影响。研究表明,“淬火-时效”试样从室温加热到320℃马氏体完全消失为止始终未发生逆相变。分级淬火短期等温试样出现B2?9R和DO_3?18R两种马氏体相变共存。随着等温时间的增长,B2?9R相变消失,与此同时DO_3?18R相变增强。然而,淬火后立即上淬到100—150℃等温的试样只出现B2?9R相变,即使等温时间增长也能继续保持。显然,从高温快冷不能抑制A2?B2有序,却可以抑制B2?DO_3有序。虽然分级和上淬处理时母相所处的湿度相同,但其有序态却各异,足够的空位浓度是发生B2?DO_3有序转变的必要条件。文中讨论了Cu-Zn-Al合金马氏体稳定化的可能机制。     

多晶Cu-Zn-Al合金变形过程中马氏体的精细结构变化SCIEI

本文利用透射电子显微镜研究了多晶Cu-Zn-Al形状记忆合金在马氏体状态的变形过程中,其精细结构的变化。结果表明:在变形的初期阶段,变形通过变体的再取向实现,但再取向常有不完全性,而且再取向后,原先变体间的界面依然存在。变形量较大时,马氏体中出现大量的孪晶,孪晶面为(001)。在局部区域出现位错。这时马氏体失去热弹性,记忆效应被破坏。     

热处理对Cu-Zn-Al形状记忆合金显微组织及回复率的影响

制备了Cu-27Zn-4.6Al(质量百分数)形状记忆合金,采用不同的工艺参数进行热处理.通过显微组织观察、XRD物相分析、形状回复率测试等对不同热处理后的样品进行了分析研究.结果显示,在850℃固溶淬火后出现板条较细小、界面平直清晰的典型马氏体组织;随着固溶温度的升高,合金的晶粒逐渐变大,形状回复率先增大后减小,850℃时达到最大.     

Ti-13at.-％Ni-37at.-％Pd记忆合金预形变与高温形状记忆效应SCIEI

本文着重地研究了Ti-13at.-％Ni-37at.-％Pd合金的高温形状记忆效应与预形变温度的关系.该合金A_s温度是620K,具有单程形状记忆效应和双程形状记忆效应。在620—640K温度预形变,可以得到最大的形状记忆应变,这与在此温区产生的最小可逆应变能有关。     

成分和热处理对CuAlNi合金相组成和有序状态的影响SCIEI

用金相、透射电镜和X射线衍射分析对三种成分的CuAlNi合金研究了成分和热处理对相组成,B2和D0_3型畴尺寸以及马氏体热弹性行为的影响。结果表明,随Al含量的增加马氏体结构类型从18R_1变到2H,并且相变温度降低。随着冷速增大,B2和D0_3型畴的尺寸减小。     

CuZnAl合金的马氏体及其相变的阻尼性能SCIEI

本文研究了CuZnAl合金在马氏体及马氏体相变时的阻尼性能。结果表明,在马氏体状态的内耗是一种M/M界面内耗,利用位错内耗理论的表达式可解释其变化规律。在马氏体相变区的内耗,包括M/M界面内耗及相变内耗两级分,其中相变内耗又由马氏体逆转变产生的内耗及应力诱发马氏体内耗两部分组成,并且前者占主导地位、合金阻尼性能的衰减与激振过程中引入的位错有关,并在一定振动次数后趋向一稳定值。     

淬火后低合金超高强钢的马氏体相变研究

研究了低合金超高强钢在淬火后的相变特征。结果表明,淬火后低合金超高强钢中出现板条状和针状两种形态的马氏体。其中板条马氏体具有较快的形成速率,并且形成温度相对较高,碳发生重新分配,板条周围出现富碳奥氏体微区。针状马氏体的形成温度相对较低,出现自回火现象,并析出细小弥散的合金碳化物。     

STABILITIY OF MARTENSITE IN Cu-Zn-Al SHAPE MEMORY ALLOY AFTER DIRECT OR STEPPED QUENCHING

The stability of thermoelastic martensite in a Cu-14.84 wt-％Zn-7.75 wt-％Al shape mem-ory alloy with M_s=106°C after direct quenching or stepped quenching has been investigatedby using TEM,X-ray diffroctometer and double electric bridge instrument.The martensiteaged for about 3 h at room temperature after either direct quenching or stepped quenching(150°C,2 rain)is the M18R structure.The martensite just directly quenched is not so stable,both its certain diffraction peaks and specific electric resistivity,change with aging at roomtemperature;whereas it is stable after stepped quenching(150°C.2 min),and its diffractionpeaks and specific electric resistivity change no more with aging at room temperature.Theabove mentioned results seem to be explained by the martensite reordering.     

ORDER STATE AND STABILITY OF MARTENSITE IN AN AIR-QUENCHED Cu-Zn-Al ALLOY

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ON THE STABILIZATION OF THERMOELASTIC MARTENSITE IN A Cu-Zn-Al ALLOY

The stabilization of thermoelastic martensite in a rapidly solidified Cu-Zn-A1 alloy is be-lieved to be the process of disordering in atomic configuration during which the structure ofmartensite gradually transforms into N9R(b/a=1/3~(1/2))from M18R.This is dependentupon the intrinsic decomposition tendency of the martensite.     

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.     

A QUENCHING INDUCED PLANAR DEFECT OF MARTENSITE IN Cu-Zn-Al ALLOY

A new kind of planar defect named non-basal plane stacking faults has been studied by usingtrace analysis and lattice image techniques.It has been found that they are located in(125)_M plane of martensite lattice.By lattice image observation,the non-basal plane stack-ing faults are argued to be induced by two incomplete basal plane stacking faults and may bethe results of rapid quenching.The defects are regarded as anomalous structures ofmartensite.     

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.     

MICROSTRUCTURE AND REVERSE SHAPE MEMORY EFFECT IN A Cu-Zn-Al ALLOY

The bainite structure in a Cu-Zn-A1 alloy related to the reverse shape memory effect hasbeen observed by means of TEM.The reverse memory effect may be improved by up to oneorder of magnitude under applied constraint stress.The widespread propagation of bainite wasconfirmed to be the diffusion controlled shear process by the parabolic configuration of sideinterface of bainite plate and the twisting of intersected bainite plates.     

Cu—Zn—Al合金逆形状记忆组织的电镜观察

用透射电镜观察了Cu-Zn-Al合金中逆形状记忆的贝氏体组织。在外加约束应力作用下,逆记忆量可以提高一个数量级,贝氏体片侧相界面的抛物线轮廓和贝氏体片交叉曲折的现象说明了贝氏体展宽是扩散控制的切变过程。