Cu－Zn－Al合金初生态贝氏体的台阶普遍性

利用透射电镜（ＴＥＭ）观察了三种不同成分的Ｃｕ－Ｚｎ－Ａｌ合金在不同等温温度（２５０，３００，３５０℃）下形成的贝氏体的显微结构．结果发现，三种合金在不同温度形成的贝氏体初生态的宽面及端面均存在三维形态的台阶，但无层错亚结构，表明台阶在Ｃｕ－Ｚｎ－Ａｌ合金贝氏体中是普遍存在的，贝氏体的生长属扩散控制的台阶长大机制．     

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。     

Cu－Zn－Al合金等温转变产物的形态及其精细结构

通过ＴＥＭ及ＳＥＭ分析研究了Ｃｕ－２５．９ｗｔ％ｚｎ－４ｗｔ％Ａｌ合金在２００～１００℃范围内等温过程中析出相的形态及内部结构的变化。初生α＿１片（贝氏体）有生长台阶，内部无层错。在其生长的第二阶段出现层错，界面处有生长台阶。第三阶段界面弯曲，层错逐渐消失，代之以位错网。片状α＿１逐步转变为块状平衡α相。实验证明，α＿１片的相变特征与各种切变长大机制不符，属扩散控制的台阶长大机制。     

Cu—Zn—Al合金中温相变产物的组织和结构

测定了Cu-27.27 Zn-3.73 Al Wt-%合金直接从高温母相淬火至中温的等温转变曲线.用金相、X-射线和电镜对直接淬火和从DO_3有序母相上淬至中温的转变产物做了形貌与结构的观察和分析.实验表明,依照转变产物,可将两个分离相接的c曲线分为三个区间:棒状α相,α相与片状贝氏体的混合组织,片状贝氏体.上淬所形成的贝氏体与直接淬火的贝氏体形貌相同.随时效时间的延长,贝氏体逐渐变成α相,它与从母相平衡析出的α相的点阵常数没有差别,由B2和DO_3母相所形成的贝氏体为接近正交的长周期结构,而且DO_3母相所形成的马氏体为单斜结构,它们分别对应(1210)与(2010)衍射峰的重叠和分离,表示前者的有序度较低.     

仪表用Al—Cu—Zn—Mg合金的双级时效

本文研究了Al-5.5Cu-4.5Zn-0.8Mg合金挤压棒经过465℃淬火后再以不同的时效制度处理,合金组织和性能变化的规律.固溶处理后合金组织中存在着较多的未溶相质点;时效时在α相基底上形成脱溶物晶核的同时,未溶相质点作为脱溶过程中化合物析出依附物而长大,在采用120℃/6小时 150℃/14小时双级时效制度的情况下,脱溶物质点的总数要比采用130℃/20小时时效的多一些.130℃时效时,合金强度(σ_b)最多能够达到382兆帕,而双级时效后σ_b最大值为404兆帕,平均值约为398兆帕,高于技术条件的要求值.     

Cu—Zn—Al形状记忆合金在马氏体状态的塑性变形

采用光学显微镜、电子显微镜、电阻和膨胀方法研究了三种Cu-Zn-Al形状记忆合金在马氏体状态的塑性变形对马氏体转变温度、相变过程及转变循环滞后的影响。其中两种合金相变温度较高,在室温下即为马氏体状态。第三种合金A_f温度远低于室温。讨论了“第一次循环效应”的可能机制。     

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。     

Zr对Cu—Zn—Al形状记忆合金相变的影响

采用示差扫描热分析(DSC)、X射线衍射及透射电镜,研究了Zr对Cu-Zn-Al合金高温相变、马氏体正逆转变以及形状记忆效应的影响。结果表明,添加Zr0.35wt-％时,能有效地抑制α,γ相析出,促进β_2→DO_3→18RM转变。(M_s-M_f)及(A_s-A_f)温度区间较窄,马氏体相变激活能最低,马氏体变体间界面的可动性好,形状记忆效应最佳。     

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.     

THE FAILURE MECHANISM OF REVERSE SHAPE MEMORYEFFECT IN A Cu-BASE ALLOY

1.IntroductionItiswellknownthatthereverseshapememoryeffect(RSME)isrelatedtobainitictransf0rmati0ninCu-baseshapememoryalloys(SMA)['l'].Thusthestructure0fbainite(a1)playsanimportantroleinthiseffect.Ref.I3]indicatesfurtherthatthereverseshapememoryeffectmaybeimprovedupt00neorder0fmagnitudeunderappliedconstraintstress-ThismeansthatRSMEunderanexternalstresshaJsabroadengineeringprospect.Inordertoelucidatethemechanism0fb0threverseshapememoryeffectandbainitictransformationinCu-basealloys,thispap…     

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.     

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

ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｓｔａｂｉｌｉｚａｔｉｏｎｏｆｍａｒｔｅｎｓｉｔｅｒｅｆｅｒｓｔｏｔｈｅｐｈｅｎｏｍｅｎｏｎｔｈａｔｔｈｅｒｅｖｅｒｓｅｔｒａｎｓｆｏｒｍａｔｉｏｎｓｔａｒｔａｎｄｆｉｎｉｓｈｔｅｍｐｅｒａｔｕｒｅｓ（ＡｓａｎｄＡｆ）ｉ...     

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。     

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.     

MARTENSITE AND REVERSE TRANSFORMATION IN PRESTRAINED TiNi SHAPE MEMORY ALLOY THIN FILM

The effect of pre-strain on phase transformation of TiNi shape memory alloy film was studied by differential scanning calorimeter measurement (DSC). Compared with un-defarmed TiNi film, the reverse transformation of pre-strained specimens was elevated to a higher temperature on the first heating, but martensite and reverse transformation on subsequent thermal cycles occurred at a lower temperature. The evolution of transformation behavior in pre-strained TiNi film was related to the change of elastic strain energy, irreversible energy and internal stress field.     

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.