形变对Ti44Ni47Nb9宽滞后形状记忆合金应力诱发马氏体相变行为的影响

采用差示扫描量热仪(DSC)系统研究了在(M8 30℃)温度下拉伸形变对Ti44Ni47Nb9形状记忆合金应力诱发马氏体(SIM)相变行为的影响．DSC测量表明，SIM相变为一微观不均匀过程，当形变量达到约14％时，SIM相变过程结束．在形变试样的第一次加热过程中，SIM的逆转变开始温度A′s和相变潜热均随着形变量的增加先增加后略有降低；而逆转变温度间隔随着形变量的增加略有增加，但和热诱发马氏体相比，SIM的逆转变温度间隔明显变窄．此宽滞后现象为一次性效应．在随后加热循环中的相变潜热、第一次冷却过程中马氏体相变开始温度以及第二次加热过程中逆转变开始温度均随着形变的增加而缓慢降低．     

Ni—Ti—Nb宽滞后形状记忆合金的形变诱发马氏体相变及其可逆性

用透射电镜、高分辨电镜、不同温度下的拉伸试验以及电阻率－温度曲线测试研究了Ｎｉ－Ｔｉ－Ｎｂ合金形变诱发马氏体相变及其可逆性，分析了形变诱发马氏体的稳定性和可逆性与其变体界面结构之间的关系。结果表明，Ｎｉ－Ｔｉ－Ｎｂ合金在Ｍｓ－Ｍｓ＾σ温度区间加应力时发生应力诱发马氏体相变，而在Ｍｓ＾σ以上温度加应力时，发生应变诱发马氏体相变。形变对Ｎｉ－Ｔｉ－Ｎｂ合金的应力诱发马氏体界面结构有明显影响，随着拉伸变     

循环应力作用下TiNi形状记忆合金应力诱发相变行为演变的原位研究

利用马氏体相变有相变潜热释放的性质,通过精确测量TiNi形状记忆合金在不同变形条件下试样温度的变化波形,结合应力应变响应研究了循环应力作用下TiNi形状记忆合金相变行为的演变过程,对循环应力造成形状记忆合金超弹性退化的原因进行了探讨.结果表明:试样的温度变化比普通金属材料高许多,可以用温度法来研究马氏体相变在变形过程中的变化;在应力控制的循环应力作用下,试样内应力诱发马氏体相变量随着循环周次的增加而不断减小,每一周内应力诱发马氏体相变行为也在不断演化,发生应力诱发马氏体相变的临界应力不断减小,而由马氏体弹性变形所携带的应力增加.     

形变对Ti-Ni-Hf高温记忆合金相变及双程形状记忆效应的影响

采用微分扫描式量热法(DSC)、拉伸试验和弯曲试验研究了形变对Ti36Ni49Hf15高温形状记忆合金相变及双程形状记忆效应的影响.结果表明,形变不影响合金的相变顺序.在马氏体状态下变形时,随形变量的增加,Ti36Ni49Hf15合金的马氏体相变温度略有下降,逆马氏体相变温度上升.当形变量一定时,合金在马氏体状态下不同温度变形,对合金的相变温度没有显著影响.Ti36Ni49Hf15高温记忆合金在马氏体状态下直接变形可以产生双程形状记忆效应,其双程可逆应变量随形变量的增加而增加.在随后的热循环过程中,合金的双程形状记忆效应在最初的几次循环过程中迅速下降,而后随循环次数的增加趋于稳定.     

Fe-Mn-Si形状记忆合金应力诱发马氏体相变的X射线分析

采用X射线衍射法对Fe-17Mn-5Si-10Cr-5Ni和Fe-17Mn-5Si-2Cr-2Ni-1V合金的应力诱发马氏体相变进行了定量的分析。研究结果表明，Fe-17Mn-5Si-10Cr-4Ni合金试样在室温下拉伸，当变形量约为6％时，应力诱发ε马氏体的体积分数达最大值约64％；在预变形量超过5％时，α‘马氏体即开始出现且增加迅速；揭示在大变形下，Fe-Mn-Si合金中发生了应力诱发γ→ε→α‘马氏体相变。Fe-17Mn-5Si-2Cr-2Ni-1V合金试样在室温拉伸时应力诱发ε马氏体量较Fe-17Mn-5Si-10Cr-4Ni合金更多，即使在预变形量超过10％时，也不出现α‘马氏体。预变形温度降低，可促进应力诱发马氏体相变。     

1Cr18Ni9Ti不锈钢形变诱发马氏体相变规律及其对孔敏感性…

通过低温（－７０℃）拉伸制备不同马氏体相变量１Ｃｒ１８Ｎｉ９Ｔｉ试样，用ＸＲＤ，ＴＥＭ及金相观察研究形变诱发马氏体相变的规律。用电化学方法研究α马氏体（铁磁相）含量对１Ｃｒ１８Ｎｉ９Ｔｉ钢在含Ｃｌ＾－溶液中孔蚀敏感性的影响，结果表明，随试样变形量加大，形变诱发马氏体中铁磁性的α马氏体含量不断增大，而ε马氏体相的量始终较小。材料的孔蚀敏感性失随铁磁相含量的增大而增大，当铁磁相含量达到４．５８％以后，     

Ti-50．8Ni-0．3Cr超弹性合金的相变与形变特性

用示差扫描量热仪、X射线衍射仪、拉伸实验和循环实验研究了退火温度、形变温度和应力-应变循环对Ti-50.8Ni-0.3Cr超弹性(SE)合金丝和弹簧相变、形变及应力循环特性的影响.350-600℃退火态Ti-50.8Ni-0.3Cr合金室温下呈SE特性,室温组织由母相B2和TiNi3组成.退火温度显著影响合金的相变类型,随退火温度升高,合金的马氏体相变温度升高,R相变温度先升高后降低,应力诱发马氏体应力先降低后升高;随形变温度的升高,SE弹簧的应力诱发马氏体切应力增加;随应力循环次数增加,SE弹簧的应变恢复率先快速衰减后趋于稳定.预循环训练可增加弹簧SE特性的稳定性.要使该合金弹簧具有良好的SE特性,退火温度应为400-550℃,使用温度应在室温以上.     

预变形对Ni-Mn-Ga合金马氏体相变的影响

研究了形变对Ni-Mn-Ga合金马氏体相变及其组织形态的影响，并应用马氏体相变热力学和动力学探讨了适当塑性变形后马氏体相变滞后得以大幅度提高的微观本质。结果表明，随着应变量的增加，马氏体相变温度几乎保持不变，而其逆相变温度则迅速升高，塑性应变导致储存在界面处的弹性应变能的释放是塑性变形提高合金相变滞后的主导因素。     

形变诱导马氏体相变循环制备304不锈钢超塑性的研究

提出了形变诱导马氏体相变实现304不锈钢超塑性的构想,研究了利用形变诱导马氏体相变循环实现超塑性的方法。结果表明,304不锈钢通过室温形变可诱导马氏体相变,随后时效时马氏体发生逆相变且伴随产生回复应力,从而间接达到了相变超塑性的实现条件。采用室温拉伸30%后在973~1273 K时效20 min,相变循环2次,该钢可实现相变超塑性,总伸长率随时效温度的增加先增加后下降,1123 K达到最大值177%;在室温拉伸30%后1073K时效30 min时,随相变循环次数增加,总伸长率增加,相变循环7次后达到764%。随相变循环次数增加,晶粒明显细化、均匀化。     

应变速率对β固溶Ti-10V-2Fe-3Al合金应力诱发马氏体相变的影响

研究应变速率对β固溶处理的Ti-10V-2Fe-3Al合金应力诱发马氏体相变的影响。结果表明,随着应变速率由5×10-4 s-1增加到1 500 s-1,合金都发生应力诱发马氏体转变,且诱发应力随着应变速率的增加而增加。金相形貌及XRD分析显示,在所有的应变率下,合金拉伸后的微观组织均由针片状α″相和β基体相组成。应用热激活界面运动模型及拉伸过程的温度升高解释了随着应变速率的增加,诱发应力增加的现象。     

Effect of deformation by stress-induced martensitic transformation on the transformation behaviour of NiTi

It has been reported that martensite in near-equiatomic NiTi is thermally stabilised after a moderate deformation via martensite reorientation. This work continues the study by investigating the effect of deformation via stress-induced martensitic transformation on the transformation behaviour of the alloy. It was observed that the stress-induced martensite was also stabilised relative to the thermal martensite formed on cooling, as indicated by an increase in the critical temperature for the reverse transformation. Associated with the stabilisation, the heat effect, as determined by differential scanning calorimetry, and the temperature interval of the reverse transformation, were measured and found to decrease with increasing level of deformation. The experimental results also demonstrated that the stress-induced martensitic transformation was microscopically localised, as expected for a first-order phase transformation.     

TiNi薄膜马氏体稳定化及其形状记忆效应研究

用DSC研究了预变形对Ti51Ni49形状记忆合金薄膜的相变行为的影响，结果表明：预变形后薄膜的马氏体发生了稳定化现象，第一次逆相变温度T^1A随预应变量增加而升高，而在第二次相变循环中，马氏体稳定化现象消失，逆相变温度T^2A基本恢复到变形前的温度值，马氏体相变温度随预应变量增大而降低，但R相变受预变形影响不大，形状记忆效应研究表明，Ti51Ni49合金薄膜的可恢复应变随预应变量的增加而增大，其最大值4．5％在预应变量为6％时获得。     

Effect of deformation on the stress-induced martensitic transformation in (Ni47Ti44)100−xNbx shape memory alloys with wide hysteresis

Martensite in TiNi-based alloys is reported to be thermally stabilized after a moderate deformation. Hence, this paper investigates the effect of deformation via stress-induced martensitic transformation on the reverse transformation behavior of (Ni₄₇Ti₄₄)_100−xNb_x (x=3, 9, 15, 20, 30 at.%) alloys. The stress-induced martensite appears to be stabilized in relation to the thermal-induced martensite that forms on cooling. This observation is confirmed by an increase in the reverse transformation start temperature, during which time the transformation temperature hysteresis reaches about 200°C. Moreover, the Nb content in Ni−Ti−Nb alloy has a great influence on the transformation temperature hysteresis of stress-induced martensite as well as on the process of stress-induced martensitic transformation. The mechanism of wide transformation temperature hysteresis is explained in terms of the microscopic structure of (Ni₄₇Ti₄₄)_100−xNb_x alloys. Furthermore, the temperature interval of the reverse transformation of stress-induced martensite was found to increase slightly as the strain of the high Nb-content alloy increased, though the value was much smaller than that of the thermally induced martensite. Finally, the paper explains the relation between this unique phenomenon and the elastic strain energy.     

Stress-induced martensitic transformation in （Ni47Ti44）100-xNbx shape memory alloys with wide hysteresis

The effect of deformation via stress-induced martensitic transformation on the reverse transformation behavior of the （Ni47Ti44）100-xNbx （x=3, 9, 15, 20, 30, mole fraction, %） shape memory alloys was investigated in detail by differential scanning calorimetry （DSC） after performing cryogenic tensile tests at a temperature of Ms＋30 ℃. The results show that Nb-content has obvious effect on the process of stress-induced martensitic transformation. It is also observed that the stress-induced martensite is stabilized relative to the thermally-induced martensite （TIM） formed on cooling, and Nb-content in Ni-Ti-Nb alloy has great influence on the reverse transformation start temperature and transformation temperature hysteresis of stress-induced martensite（SIM）. The mechanism of wide transformation temperature hysteresis was fully explained based on the microscopic structure and the distribution of the elastic strain energy of （Ni47Ti44）100-xNbx alloys.     

Stabilisation of martensite due to shear deformation via variant reorientation in polycrystalline NiTi

The effect of deformation via martensite reorientation on the transformation behaviour of polycrystalline near-equiatomic NiTi was studied. Differential scanning calorimetry measurement showed that both the critical temperature and the endothermic heat of the first reverse transformation of the deformed martensite were increased as compared to an undeformed specimen, indicating a stabilisation effect to the reoriented martensite. Thermal dilatation measurement revealed a two-way memory effect in subsequent transformation cycles after the deformation, suggesting that an anisotropic internal stress field had been established. X-ray diffraction measurement showed a systematic line broadening on the major diffraction peaks with increasing amount of deformation. These experimental observations are discussed in terms of the changes in the internal elastic and irreversible energies associated with the reorientation deformation in a polycrystalline matrix.     

两种不同变形方式对NiTi合金回复特性的影响

研究了马氏体再取向(MR)和应力诱发马氏体转变(SIM)两种不同变形方式对Ni50.2Ti49.8合金拉伸性能及预应变后加热回复特性的影响.结果表明:拉伸变形中,MR变形方式的应力平台结束时的应变值较SIM变形方式大.在拉伸预应变处于应力平台阶段时,两种变形方式在相同预应变后加热回复有相同的记忆能力;在拉伸预应变大于应力平台时,两种变形方式在相同预应变后加热回复,SIM变形方式的逆相变温度和回复应变略高于MR变形方式.     

MARTENSITE TRANSFORMATION OF A TiNiCu ALLOY

ＭＡＲＴＥＮＳＩＴＥＴＲＡＮＳＦＯＲＭＡＴＩＯＮＯＦＡＴｉＮｉＣｕＡＬＬＯＹ￥Ｚｈａｎｇ，Ｙｉ；Ｊｉｎ，Ｊｉａｌｉｎｇ；Ｊｉ，Ｚｈｉｑｉａｎｇ（ＳｈａｎｇｈａｉＩｒｏｎａｎｄＳｔｅｅｌＲｅｓｅａｒｃｈＩｎｓｔｉｔｕｔｅ，Ｓｈａｎｇｈａｉ２００９４０）...     

Microstructure and transformation behavior of Ni50Ti45Ta5 shape memory alloy

1　INTRODUCTIONTheNiTishapememoryalloy (SMA )iscur rentlyatopicofnotableinterestinmedicine .Itpro videsauniqueopportunitytomakenovelsurgicalim plantsandinstrumentsforminimallyinvasive ,vascu larandorthopedicsurgery .Recently ,NiTiimplantshavebeendevelopedforcardiovascularandgastroin testinalsurgery[13] .ThehighnickelcontentofNiTi(5 4%bymass)cancauseproblemsinbiocompati bilitybecauseoftoxiceffectsofnickel[4 ] .Moreover ,thelowX rayvisibilityofNiTiSMAhaslimitedsomemedicalapplications …