Cu-Al-Mn合金马氏体结构及其在时效过程中的变化

利用X射线衍射、透射电镜观察等方法研究了Cu 11 9Al 2 5Mn合金的马氏体结构及其在时效过程中的变化。该合金淬火态马氏体为单斜 18R结构 (M18R) ,点阵常数为 :a =0 4 4 75nm ,b =0 5 2 2 9nm ,c=3 815nm ,β =89 6°。特点是单斜角β很大 ,已非常接近正交 18R结构 (N18R) ;马氏体内存在两种类型的面缺陷 ,一种是基面堆垛层错 ,另一种是非基面堆垛层错 ;时效时马氏体由单斜向正交转变的过程在一定程度上受到抑制 ,因而具有较高的抗马氏体稳定化的能力。     

时效对Cu-Zn-Al合金热弹性马氏体转变的影响

本文用直流电阻法研究了时效对M_s点高于室温的工业纯Cu—Zn—Al合金热弹性马氏体转变的影响。若该合金从高温无序β相区淬火后立即在马氏体状态充分时效,则热弹性马氏体会发生稳定化,在升降温的电阻—温度曲线上,马氏体不再呈现热弹性正逆转变的特征;若该合金淬火后立即在β_1状态(母相状态)时效,则随着β_1状态时效时间的延长,合金马氏体的热弹性转变特性会逐步保持下来,其马氏体相变点和马氏体相对可逆转变量逐渐趋近一稳定值,在随后的热循环中它们变化很小.可以认为,马氏体态时效所引起马氏体的稳定化与马氏体的再有序化及过饱和空位的聚集等过程有关。     

EFFECT OF AGING ON THERMOELASTIC MARTENSITE TRANSFORMATION IN Cu-Zn-Al ALLOY

本文用直流电阻法研究了时效对M_s点高于室温的工业纯Cu—Zn—Al合金热弹性马氏体转变的影响。若该合金从高温无序β相区淬火后立即在马氏体状态充分时效,则热弹性马氏体会发生稳定化,在升降温的电阻—温度曲线上,马氏体不再呈现热弹性正逆转变的特征;若该合金淬火后立即在β_1状态(母相状态)时效,则随着β_1状态时效时间的延长,合金马氏体的热弹性转变特性会逐步保持下来,其马氏体相变点和马氏体相对可逆转变量逐渐趋近一稳定值,在随后的热循环中它们变化很小.可以认为,马氏体态时效所引起马氏体的稳定化与马氏体的再有序化及过饱和空位的聚集等过程有关。     

热处理对Ti-49.8Ni-1.0Co超弹性合金相变行为的影响

用示差扫描量热仪研究了Co对Ti-Ni合金相变特性的影响,以及退火和时效工艺对Ti-49.8Ni-1.0Co(原子分数,%)合金相变行为的影响.结果表明, Co不影响Ti-Ni合金的相变类型,但降低其相变温度,以1.0Co分别取代等量Ti和Ni后,该合金的马氏体相变温度分别降低了109和22℃. 350-450℃退火态Ti-49.8Ni-1.0Co合金冷却/加热时发生A→R→M/M→R→A(A为母相, R为R相, M为马氏体)型可逆相变: 500-550℃退火态合金发生A→R→M/M→A型相变;600℃以上温度退火态合金发生A→M/M→A型相变.随着时效时间的延长,300℃时效合金的相变类型由A→R→M/M→R→A向A→R/R→A转变;400℃时效合金的相变类型由A→R/R→A向A→R→M/M→R→A再向A→R→M/M→A转变;500℃时效合金的相变类型则保持A→R→M/M→A型不变.给出了退火温度及其时间和时效温度及其时间对R和M相变温度和热滞的影响规律.     

Ti-50.8Ni合金的相变、形状记忆和超弹性特性

用热重分析仪、X射线衍射仪、光学显微镜、示差扫描热分析仪和拉伸试验研究了Ti-50.8Ni形状记忆合金的组织、相变、形状记忆效应(SME)和超弹性(SE)特性。结果表明,Ti-50.8Ni合金在600℃以下退火后组织呈纤维状,在该温度以上退火后组织呈等轴状。加热温度超过600℃后合金氧化加剧。随退火温度Ta升高,合金冷却/加热过程中的相变类型由A→R→M/M→R→A型向A→R→M/M→A型再向A→R/R→A型转变(A—奥氏体,R—R相,M—马氏体),合金的M相变温度升高,R相变温度降低,M相变热滞降低,合金室温特性由SME+SE向SE转变。形变温度Td<20℃时,合金弹簧呈SME+SE,Td>30℃时,合金弹簧呈SE。随Td升高,合金弹簧的应力诱发M应力升高。     

退火温度对Ti-51.1Ni形状记忆合金显微组织和相变行为的影响

用X射线衍射仪、示差扫描量热仪和光学显微镜研究了退火温度对Ti-51.1Ni形状记忆合金相组成、显微组织和相变行为的影响。结果表明,350～700℃退火态Ti-51.1Ni合金室温下相由母相B2和马氏体B19'组成。随退火温度(T_a)升高,合金经历回复、再结晶、晶粒长大过程,显微组织逐渐从纤维状向等轴状转变,再结晶温度约为600℃。随T_a升高,合金的冷却/加热相变类型由A→R→M/M→R→A型向A→R→M/M→A型转变(A-母相B2,CsCl型结构;R-R相,菱方结构;M-马氏体B19',单斜结构),T_a高于650℃后R和M相变峰消失。随T_a升高,合金的马氏体相变温度先升高后降低,R相变温度降低,R相变热滞在6.3～8.3℃之间变化。     

热处理对激冷Ti-50Ni合金薄带相变和形状记忆行为的影响

用甩带法制备了Ti-50Ni形状记忆合金薄带,用X射线衍射仪、扫描电镜、透射电镜、示差扫描量热仪和弯曲试验研究了Ti-50Ni合金薄带的相组成、显微组织、相变行为和形状记忆效应。结果表明,铸态和400~600℃退火态Ti-50Ni合金薄带的显微组织形态呈树枝状,由马氏体相B19'和母相B2组成,加热/冷却过程中发生A→R→M/M→R→A(A-母相,R-R相,M-马氏体)二阶可逆相变。随退火温度升高,Ti-50Ni合金薄带的相组成和显微组织形态变化不大;马氏体逆相变温度T_A、R正相变温度T_R、R逆相变温度T_(Rr)和马氏体相变热滞ΔT_M升高,马氏体正相变温度T_M下降,R相变热滞ΔT_R缓慢降低;M逆相变峰向高温移动,逐渐与R逆相变峰合并。铸态和退火态Ti-50Ni合金薄带皆具有良好的形状记忆效应。     

Zr对CuZnAl形状记忆合金马氏体稳定化的影响

研究了添加Zr元素后CuZnAl合金的形状记忆性能和微观组织,并分析了Zr对合金马氏体稳定化的影响.结果表明,CuZnAl三元合金的形状记忆性能随时效时间的延长而逐渐下降,发生了明显的马氏体稳定化现象;而CuZnAlZr四元合金的形状记忆性能却不随时间的延长而变化,说明Zr能明显地改善合金的马氏体稳定化现象;添加Zr后,CuZnAl合金的形状记忆性能虽然有所下降,但其晶粒明显细化,力学性能得到改善,因此CuZnAlZr合金具有好的工程应用前景.     

添加Cr对Ti-Ni形状记忆合金氧化行为和相变特性的影响

研究了添加Cr对形变退火态Ti-50.8Ni形状记忆合金氧化行为及组织和相变特性的影响.结果表明,添加微量Cr后,Ti-Ni合金的再结晶温度和抗氧化能力有所降低,相变热滞增加,相变温度大幅度降低.随退火温度升高,Ti-50.8Ni合金冷却/加热时的相变类型发生由A→R→M/M→R→A型向A→R→M/M→A型再向A→M/M→A型转变(A-母相,R-R相,M-马氏体),Ti-50.8Ni-0.3Cr的相变类型发生由A→R/R→A型向A→R→M/M→R→A型再向A→R→M/M→A型再向A→M/M→A型转变.随退火温度升高,二合金的R相变温度和M相变热滞降低,M相变温度升高,R相变热滞变化不大,保持在4 ℃左右.     

钢中奥氏体的稳定化

1、前言高炭钢与合金钢淬火时存在百分之几以上的残余奥氏体。奥氏体(以下称Υ)向马氏体的相变变得困难之现象称之为Υ的稳定化。未相变的Υ是否残余是由Υ的稳定化     

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.     

Crystal structure and thermal stability of martensite in Cu-24Al-3Mn alloy

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Cu-25Al-3Mn形状记忆合金淬火态马氏体亚结构特征及其在加热过程中的变化

利用透射电镜、选区电子衍射等手段研究了Cu—25A1—3Mn形状记忆合金淬火态马氏体亚结构特征及其在加热过程中的变化。实验合金淬火态马氏体内部亚结构为(121^-)2H孪晶，该合金马氏体中产生T谱的孪晶是一些具有不同厚度的、平行入射电子束的片状非相干散射体，孪晶亚结构中最薄孪晶片厚度小于2．02nm；在加热过程中，部分2H马氏体向18R马氏体转变，出现了层错亚结构特征。     

FINE STRUCTURE VARIATION OF 18R MARTENSITE UNDER DEFORMATION IN POLYCRYSTALLINE CuZnAl AI JOY

The transmission electron microscopy has been used to investigate the fine structure variationof 18R martensite under deformation in a polycrvstalline CuZnAl shape memory alloys.Ithas been found that the strain is gabined by the reorientation of martensite variants in the ini-tial deformation stage.In addition to the result of optical microscopy studies,however,thereorientation is often incomplete and the interfaces among the prior variants still remain.A lotof twins will appear in martensite under enormous deformation,and the twin plane is(001)phane of martensite lattice.The dislocations has also been observed in some regions.In thiscase,the martensite will lose its thermoelasticitv and the shape memory effect will bedamaged.     

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…     

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.     

Microstructure and diffraction pattern changes resulted from long—term aging of martensite CuZnAlMnNi shape memory alloy

Microstructures of a CuZnAlMnNi shape memory alloy in the as-quenched and long-term aged conditions were investigated by transmission electron microscopy.Aged for one year in martensite phase,an equilbrium α-phase with fcc structure was observed in the M18R martensite matrix,accompanied by the appearance of a novel diffractionn pattern.By analysis,it was suggested that the novel pattern results from the α-phase and the martensite matrix remaining in seven fine plates which produce intense secondary diffraction effect when the diffraction beams enter from one phase into another.     

A Detailed Observation on Successive Stress-Induced Martensite Transformation in CuAlMnZnZr Alloy Polycrystalline Above Af

The successive stress-induced martensite morphologies and mechanisms in polycrystalline CuA1MnZnZr samples have been examined. By applying stress to the uniform β１ matrix, two or more orientation plates of M18R martensite are stress-induced in a grain. With further increasing stress, one orientation plate depletes the other and coalesces into a single region in some view field. The mechanisms by which these are developed have been ascertained, and include variant-variant coalescence, stress-induced martensite to martensite transformation and the complicated cross-like stress-induced martensite formation.