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.     

Cu-Zn-Al形状记忆合金直接淬火和分级淬火后马氏体稳定性的研究SCIEI

用透射电镜,X射线衍射仪和电阻法研究了Cu-14.84wt-％Zn-7.75wt-％Al形状记忆合金在直接淬火和分级淬火后马氏体的稳定性。试验结果表明,直接淬火和分级淬火(150℃,2min)后于室温时效约3h的马氏体均为M18R结构,但刚直接淬火后马氏体并不稳定,其某些衍射峰位置和电阻率均随室温时效而变化;而分级淬火(150℃,2min)后马氏体是稳定的,其所有衍射峰位置和电阻率几乎不随室温时效而变化。上述结果可用“马氏体再有序化机制”解释。     

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。     

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.     

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.     

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.     

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.     

STABILIZATION OF MARTENSITE AND PARENT PHASE ORDERING IN A Cu-Zn-Al ALLOY

The reverse transformation has never occurred in a quenched and aged specimen upon heatingfrom room temperature to 320℃ at which the martensite disappears thoroughly.Both B29R and DO_318R coexist in step-quenched and short-time isothermally treated specimen.As prolonging the isothermal holding,the B29R disappears and DO_318R intensifies.B29R occurs only in specimen quenched and up-quenched immediately to 100—150℃.Rapid quenching from high temperatures will depress the B2→DO_3 ordering but not the A2→B2 one.A plenty enough concentration of vacancy is a necessary condition of occurrence ofB2→DO_3 ordering.The possible mechanism for the stabilization of martensite in aCu-Zn-Al alloy was also discussed.     

ORDERING OF BAINITE IN A Cu-Zn-Al ALLOY

The ordering of bainite is studied and compared with that of martensite in a Cu-20Zn-6Al(wt—％) alloy by X-ray analysis. Experilnental results show that in contrast with the diffraction pattern for 9R or 18R martensite, in which the (115) diffraction peak is distinguishable from the (■ 0 5), and the (1 2 10) from the (2 0 10), the (1 1 5) and (■ 0 5) or the (1 2 10) and (■0 10) diffraction peaks in the bainites formed from high temperature B2 or low temperature L2 parent phase overlap, and these phenomena do not change after prolonged aging or slow-cooling. The bainite structure is quite different from that of the martensite, i. e., the inheritance of the ordering of the parent phase would not occur, during bainite formation.     

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。     

STABILIZATION OF MARTENSITE IN Cu Zn Al ALLOY AND ITS REVERSE SHAPE MEMORY EFFECT

ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｓｔａｂｉｌｉｚａｔｉｏｎｏｆｍａｒｔｅｎｓｉｔｅｒｅｆｅｒｓｔｏｔｈｅｐｈｅｎｏｍｅｎｏｎｔｈａｔｔｈｅｒｅｖｅｒｓｅｔｒａｎｓｆｏｒｍａｔｉｏｎｓｔａｒｔａｎｄｆｉｎｉｓｈｔｅｍｐｅｒａｔｕｒｅｓ（ＡｓａｎｄＡｆ）ｉ...     

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。     

DEFORMATION BEHAVIOUR OF Cu－Zn－Al ALLOYS AND ITS EFFECT ON TRANSFORMATION HYSTERESIS

ＤＥＦＯＲＭＡＴＩＯＮＢＥＨＡＶＩＯＵＲＯＦＣｕ－Ｚｎ－ＡｌＡＬＬＯＹＳＡＮＤＩＴＳＥＦＦＥＣＴＯＮＴＲＡＮＳＦＯＲＭＡＴＩＯＮＨＹＳＴＥＲＥＳＩＳＷａｎｇＭｉｎｇｐｕ；ＸｕＧｅｎｙｉｎ；ＹｉｎＺｈｉｍｉｎｇ（ＤｅｐａｒｔｍｅｎｔｏｆＭａｔｅｒｉａｌ...     

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。     

TRANSFORMATION HYSTERESIS AND STABILITY OF STRAIN MARTENSITE IN A Ni_(47)Ti_(44)Nb_9 ALLOY

The transformation hysteresis and stability of strain martensite in Ni_(47)Ti_(44)Nb_ alloy have been studied by means of tensile tests at various temperatures and electrical resistance measurements as well as TEM observations.It was shown that there is a characteristic deformation temperature and a strain range,in which the critical yield stress for stress-in- duced transformation acquires optimum matching with the yield strength of the β-Nb parti- cles.In this case,deformatian can effectively increase the transformation hysteresis,while the strain recovery ratio remains usefully high.The martensite with irreguldar fine.twin substructure and martensite containing some dislocations as well as martensite intersected by the β-Nb particles possess high stability.     

淬火在Cu—Zn—Al合金马氏体中引入的一种新缺陷

本文报道了Cu-Zn-Al合金中18R马氏体里存在的一类新的面缺陷。实验结果的统计表明,在由高温直接淬入冰水中的样品里,马氏体中常出现非基面上的层错。衍衬分析证明,这种层错常位于(125)_M面上。通过对晶体结构和处理条件分析,提出了这种层错出现的机制,并给出了层错的结构模型。     

THE TYPE II DEFECT IN 18R MARTENSITE IN A Cu-Zn-Al ALLOY

1'IntroductionMartensitephaseswiththe9R0rthel8Rstructurehavebeenf0undinmanyP-phaseHume-R0theryall0ys.Inpracticethel8R(0r9R)stackingsequenceishardlyeverperfectandahighdensityofrand0mlydistributedbasalstackingfaultsare0ften0bserved[1-4].Apartfr0mthebasalplanefaults,thepresenceof0therplanardefects,suchasTypeI0rTypeII,haJsbeenreportedI'-"].Inreference[9],itismenti0nedthatdefectsofTypeIandTypeIIarereferredt0asdefectsnearlyparallelt0aplanecrystallographicallyequivalenttothehabitplane(cl0set0…     

Cu-25Al-3Mn合金马氏体结构及其内部缺陷

利用金相观察、Ｘ射线衍射、透射电镜分析等方法研究 Ｃｕ－２５Ａｌ－３Ｍｎ（原子分数，％）合金马氏体结构． 确认该合金淬火态为有序Ｍ２Ｈ型马氏体，其基面原子分布为：Ａｌ原子占据顶角；Ｃｕ原子占据面心；原子占据ｂ边中点，其点阵常数 ａ＝０．４４５９ ｎｍ，ｂ＝０５２７９ ｎｍ，ｃ＝０．４２４１ ｎｍ，β＝８８６４°合金马氏体内发现有由变体群形成的一种三角形组态及其它复杂组态．     

Cu-Zn-Al合金中马氏体穿晶界生长过程的动态观察

合金中的马氏体是晶体点阵切变的产物,对于多晶材料,马氏体通常在各个晶粒中形核长大,但不跨越晶界,然而在Cu-Zn-Al形状记忆合金的研究中,我们观察到了马氏体穿晶界生长现象。记忆合金中的马氏体相变具有热滞后和驱动力小等特点,称为热弹性马氏体相变,马氏体穿晶界生长可能也是这类相变的一个特征。该现象既涉及马氏体相变理论本身,又与晶界问题密切相关,应该成为一个有趣的研究课题。