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.     

Correlation between liquid structure and γ2-phase precipitation of Cu-Al-Ni shape memory alloys

1　ＩＮＴＲＯＤＵＣＴＩＯＮＣｕ ｂａｓｅｓｈａｐｅｍｅｍｏｒｙａｌｌｏｙｓ (ＳＭＡ)ａｒｅｃｏｍ ｍｅｒｃｉａｌｌｙａｔｔｒａｃｔｉｖｅｓｙｓｔｅｍｓｆｏｒｔｈｅｐｒａｃｔｉｃａｌｅｘｐｌｏｉｔａ ｔｉｏｎｏｆｔｈｅｓｈａｐｅｍｅｍｏｒｙｅｆｆｅｃｔ (ＳＭＥ     

THE STRESS-STRAIN-RESISTANCE RELATIONS IN Fe-Mn-Si ALLOYS

1. IntroductionThe strain sensitivity coefficients of resistance, K, have a value of about 2.0 in elasticregion for most alloys, such as constantan (a Cu-Ni alloy), karma (a Ni--Cr based alloy)and Fe-Cr-Al alloy, except Pt-W alloys. The K values are also about 2.0 in plastic regionfor the most alloys. For the ac--Fe--Mn-Al-Cr alloy it is also about 2.0 during plastic transformation, however, it becomes as high as 4.0--4.8 due to the antiferromagnetic transitionbelow the N6el temperature,…     

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。     

Co对Ti-Ni形状记忆合金相变和形变特性的影响

用热重分析仪、X射线衍射仪、示差扫描量热仪及拉伸试验研究了Co对Ti-49.8Ni(at%,下同)形状记忆合金相变和形变特性的影响。结果表明,中温退火态Ti-49.8Ni合金冷却/加热时的相变类型为A→R→M/M→A(A—母相,R—R相,M—马氏体相);随退火温度升高,该合金的马氏体相变温度升高,R相变温度先升高后降低;该合金室温相组成为马氏体,具有形状记忆效应(SME)。用1%Co置换等量Ti后所得Ti-49.8Ni-1Co合金冷却/加热时的相变类型为A→R→M/M→R→A,相变温度低,室温组成相为母相A,具有超弹性(SE)特性。退火温度低于600℃时,Ti-Ni基合金的SME和SE特性良好,退火温度超过600℃后,合金氧化加剧,SME和SE特性变差,塑性显著提高。     

INFLUENCE OF PROCESSING ON SHAPE MEMORY EFFECT OF Fe-Mn-Si-Ni-C-RE SHAPE MEMORY ALLOY

Effect of carbon, compound RE, quenching temperature, pre-strain and recovery temperature on shape memory effect (SME) of Fe-Mn-Si-Ni-C-RE shape memory alloy was studied by bent measurement, thermal cycle training, SEM etc. It was shown that the grains of alloys addition with compound RE became finer and SME increased evidently. SME of the alloy was weakening gradually as carbon content increased under small strain (3%). But in the condition of large strain (more than 6%), SME of the alloy whose carbon content range from 0.1% to 0.12% showed small decreasing range, especially of alloy with the addition of compound RE. Results were also indicated that SME was improved by increasing quenching temperature (>1000℃). The amount of thermal induced martensite increased and the relative shape recovery ratio could be increased to more than 40% after 3-4 times thermal training. The relative shape recovery ratio decreased evidently depending on rising of pre-strain. Furthermore, because speed of martensite transi     

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.     

添加Cr对Ti-Ni形状记忆合金相变和低温形变特性的影响

用示差扫描量热仪和拉伸试验研究了添加Cr对形变退火态Ti-Ni形状记忆合金相变和低温形变特性的影响。结果表明,添加微量Cr后,Ti-Ni合金的R、马氏体(M)相变温度θR和θM大幅度降低,M相变热滞?θM增加,应力-应变曲线的平台应力σM显著提高,超弹性(SE)改善,塑性变差。添加微量Cr后,Ti-Ni合金的低温SE特性大幅改善。室温下,Ti-50.8Ni合金呈现形状记忆效应(SME)+SE,而Ti-50.8Ni-0.3Cr合金则呈现SE。退火温度也显著影响Ti-Ni合金的低温形变特性。在10℃变形时,400～500℃退火态Ti-50.8Ni合金呈现SME,550～650℃退火态Ti-50.8Ni合金呈现SME+SE,而400～650℃退火态Ti-50.8Ni-0.3Cr合金则持续呈现SE。     

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。     

形变温度对FeMnSiCrNiC合金第二相方向性析出及记忆效应的影响

基于控制第二相方向性析出提高铁基合金形状记忆效应的构想,研究了不同形变温度对Fe13.53Mn4.86Si8.16Cr3.82Ni0.16C合金γ/ε界面(母相丫与诱发马氏体ε之间界面)的数量和结构及随后时效第二相析出的数量和方向性的影响,以及第二相析出的数量和方向性对马氏体相变和形状记忆效应的影响.扫描电镜分析显示,形变温度远高于Ms时,无γ/ε面产生,时效后第二相析出少;形变温度接近Ms时,产生大量γ/ε面,时效后析出第二相数量很多,且方向性良好;形变温度进一步接近Ms时,γ/ε界面交叉,导致时效后方向性的第二相也交叉.透射电镜分析显示,析出方向性Cr23C6第二相的合金再次进行预变形时,产生的应力诱发马氏体具有单一方向.原因在于方向性Cr23C6及其产生的应力场对马氏体相交产生约束作用,避免马氏体片之间的交叉,使其具有更好的可逆转变性.     

Role of thermal martensite in shape memory effect of CoAl and CoNi alloys

To address the role of the HCP martensite in CoAl and CoNi shape memory alloys, the relationship between the shape memory effect (SME) and the content of the thermal and stress-induced HCP martensite was investigated in the solution-treated CoAl and CoNi alloys. In-situ optical observations were employed to investigate the contents of thermal HCP martensite before and after deep cooling and its influence on the stress-induced HCP martensite transformation and SME. The results show that the SME in both the CoAl and the CoNi alloys results from the stress-induced HCP martensite. The role of the thermal HCP martensite in both of them is the strengthening of the matrix. The much higher yield strength in the solution-treated CoAl alloy due to solution strengthening of Al is responsible for its better SME compared with the CoNi alloy.     

铜基形状记忆合金研究中X-射线衍射分析技术的应用

运用X-射线衍射分析技术研究了不同成分铜基形状记忆合金淬火态马氏体结构、马氏体状态非等温时效过程中结构的变化规律、母相状态时效和连续变形过程中马氏体及母相结构的变化规律以及热循环过程中马氏体结构的变化情况。     

温度对Ni-Cr-Al合金中Cr原子替代规律的影响

利用微观相场动力学模型,模拟研究温度对Ni-12at%Cr-14.5at%Al合金沉淀过程中Cr原子的替代规律。在873～1173K范围内,随着温度的提高,合金沉淀机制由等成分有序化+失稳分解转化为非经典形核机制,沉淀孕育期逐渐延长;L12相体积分数增加,而D022相体积分数减少,在1173K时,D022相消失,最终形成单一的L12相。     

EFFECT OF QUENCHING TEMPERATURE ON SHAPE MEMORY EFFECT OF Fe 18Mn 5Si 8Cr 4Ni ALLOY

１．ＩｎｔｒｏｄｕｃｔｉｏｎＩｔｈａｓｂｅｅｎｒｅｐｏｒｔｅｄｔｈａｔＦｅＭｎＳｉＣｒＮｉｓｈａｐｅｍｅｍｏｒｙａｌｌｏｙｓｅｘｈｉｂｉｔｎｏｔｏｎｌｙａｇｏｏｄｓｈａｐｅｍｅｍｏｒｙｅｆｆｅｃｔ（ＳＭＥ）,ｂｕｔａｌｓｏａｇｏｏｄｃｏｒｒｏｓｉｏｎｒｅｓｉｓｔａｎｃｅ〔１,２〕,ｃｏｍｐａｒｅｄｗｉｔｈＦｅＭｎＳｉａｌｌｏｙｓ．Ｆｕｒｔｈｅｒｍｏｒｅ,ｉｔｃａｎｂｅｕｓｅｄｉｎｍａｎｕｆａｃｔｕｒｉｎｇｐｉｐｅｃｏｕｐｌｉｎｇｓｂｅｃａｕｓｅｏｆｉｔｓｈｉｇｈｐｈａｓｅｔｒａｎｓｆ…     

CuZnAlSMA形状记忆处理新工艺—瞬时高温分级淬火

本文实验表明,采用瞬时高温分级淬火工艺能有效地抑制CuZnAlSMA的马氏体稳定化。用该工艺处理的试样具有长期、稳定、良好的SME和RSME,其A_s温度基本上不受室温时效时间之影响。用本工艺处理试样作元件开发的冷端温度补偿器和密封式定温控测器工作可靠、精度高。由此得出瞬时高温分级淬火工艺是很有前途的形状记忆处理工艺。     

EFFECTS OF HEAT TREATMENT ON THE MICROSTRUCTURE OF Cu-Zn-Al (RE) SHAPE MEMORY ALLOYS

1. Introduction Cu-Zn-Al shape memory alloys have extensive application prospects because of their unique properties and low cost. However, some elements have to he added into Cu-Zn- Al shape memory alloys in order to refine their grains and to improve their mechanical properties. Some works indicated that adding rare earth (RE) elements or mixed RE (La+Ce) could improve the related properties remarkably[13]. The effects of RE addition are as the following: (1) refining grains of the al…     

时效时间对Cu-Al-Mn-Ti形状记忆合金的影响

利用弯曲实验、金相显微镜、扫描电镜、X射线衍射等现代检测手段研究了Cu-24A1-3Mn-2Ti(原子分数,%,全文同)合金进行不同时间的母相时效处理后的合金记忆效应和组织形态.结果表明:Cu-Al-X系形状记忆合金中,Mn和Ti的加入细化了组织,并且形成了富Mn和富Ti相,起到沉淀强化和弥散强化的作用;对于同一种变形量,合金在母相时效时,形状记忆效应随时效保温时间呈现规律性变化,不同时效温度下,合金对应一个不同的时效时间,此时合金的显微组织呈现最佳自协作状态,马氏体板条细密有序,富Ti和Al相均匀的弥散在组织中,合金中没有或很少有共析相出现,且随着时效时间的延长,在不同的特定温度下,Cu-24Al-3Mn-2Ti合金的组织会有规律性的变化.     

铜基形状记忆合金时效过程中的原子有序态变化

高温Ｘ射线衍射及原位电阻测量等实验结果表明，淬火态Ｃｕ—Ａｌ—Ｎｉ—Ｍｎ—Ｔｉ形状记忆合金在母相和马氏体状态时效过程中，原子有序态的演变及时效机制是不同的．在母相态时效，先发生ＤＯ_３再有序化，随后发生原子短程无序或偏聚并进而析出贝氏体或平衡相．在马氏体状态时效，ＤＯ_３长程有序度无显著变化，没发生类似在母相态的再有序化，主要是原子短程无序化．     

Factors Influencing the Reversion of Stress-induced Martensite to Austenite in a Fe-Mn-Si-Cr-Ni Shape Memory Alloy

It is well known that one way shape memory effect (SME) in Fe-Mn-Si-based shape memory alloys (SMAs) is related to the thermally induced reversion of ε (hexagonal close packed, hcp) stress-induced martensite (SIM) to γ (face centered cubic, fcc) austenite. In the case of a Fe-Mn-Si-Cr-Ni SMA, this reverse martensitic transformation was analyzed in regard to the critical temperature for the beginning of austenite formation (A _s) in different states characterized by quenching temperature and permanent tensile strain. For this purpose, dynamic mechanical analysis (DMA), dilatometry (DIL), differential thermal analysis (DSC), and optical microscopy (OM) were employed to determine the influence of quenching temperature and permanent tensile straining on SIM reversion to austenite during heating.     

固溶时效处理对TC6合金组织与性能的影响

采用OM、SEM、XRD、维氏硬度以及力学性能测试等方法,研究了固溶时效处理对TC6合金显微组织、相结构以及力学性能的影响。结果表明：TC6合金经过900 ℃固溶处理后,合金由片层α相、针状马氏体α′相以及β相组成;而经过1000 ℃固溶处理后,合金主要由针状α′马氏体相和β相组成。对不同固溶温度下的合金样品进行时效处理,针状α′马氏体相完全分解为α相和β相。并且随着时效温度升高,β相的相对含量逐渐增大。通过对比,TC6合金经过900 ℃固溶后在500 ℃下进行时效处理后综合力学性能达到最佳,此时的抗压强度和屈服强度为2000 MPa、1061 MPa,硬度值为499 HV0.2。