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.     

γ—Mn基合金双程形状记忆效应特性的研究

运用XRD研究了80％Mn—19％Cu—1％Ni合金马氏体晶格常数c、a随温度变化的趋势和在—定的预应变条件下，显微应变与温度、显微应变与形变恢复率的关系，研究了Ms点随塑性变形率变化的规律，由此研究7—Mn基合金马氏体的双程形状记忆效应的结构机制，结果表明：fct马氏体的塑性变形不但由滑移产生，而且可以由孪晶的重新取向而造成，而后者在微小的外应力作用下就可以实现，并且在形状恢复过程中，滑移和孪晶所起的作用不同，由于滑移而产生的变形，在马氏体逆相变中不能恢复，而那些具有c、a轴择优取向的变形微区和具有马氏体织构的微区，能够由马氏体逆相变即缸结构变为fcc结构，使形状得到恢复。     

γ-Mn基合金双程形状记忆效应特性的研究

运用XRD研究了 80 %Mn - 19%Cu - 1%Ni合金马氏体晶格常数c、a随温度变化的趋势和在一定的预应变条件下 ,显微应变与温度、显微应变与形变恢复率的关系 ,研究了Ms点随塑性变形率变化的规律 ,由此研究γ -Mn基合金马氏体的双程形状记忆效应的结构机制 ,结果表明 :fct马氏体的塑性变形不但由滑移产生 ,而且可以由孪晶的重新取向而造成 ,而后者在微小的外应力作用下就可以实现 ,并且在形状恢复过程中 ,滑移和孪晶所起的作用不同 ,由于滑移而产生的变形 ,在马氏体逆相变中不能恢复 ,而那些具有c、a轴择优取向的变形微区和具有马氏体织构的微区 ,能够由马氏体逆相变即fct结构变为fcc结构 ,使形状得到恢复。     

Ni—Ti合金中双程形状记忆速动相变的研究

利用应力对双程形状记忆合金中相变驱动力的制约作用,在Ni-Ti合金中实现了不需附加机构的速动相变和速动双程形状记忆效应。     

NiTi合金的显微组织和双程形状记忆效应

通过弯曲试验和透射电镜分析系统研究了热处理工艺、形变量、形变温度对ＮｉＴｉ合金双程形状记忆效应和显微组织的影响,结果表明,冷轧变形试样经不同温度退火后,双程可逆应变量随退火温度的升高而增大,退火温度超过５５０℃后,温度继续升高,双程可逆应变量基本不变,同一温度退火的试样,双程可逆应变量随弯曲形变量的增加而增加,至形变量ε１＝１２％时达到最大值;ε１进一步增加,双程可逆应变量呈下降趋势。弯曲形变量相     

NiTi合金的显微组织和双程形状记忆效应

通过弯曲试验和透射电镜分析系统研究了热处理工艺、形变量、形变温度对NiTi合金双程形状记忆效应和显微组织的影响。结果表明 ,冷轧变形试样经不同温度退火后 ,双程可逆应变量随退火温度的升高而增大 ,退火温度超过 550℃后 ,温度继续升高 ,双程可逆应变量基本不变。同一温度退火的试样 ,双程可逆应变量随弯曲形变量的增加而增加 ,至形变量εt=12 %时达到最大值 ,εt 进一步增加 ,双程可逆应变量呈下降趋势。弯曲形变量相同时 ,弯曲温度升高 ,双程可逆应变量εt 减小 ,形变温度超过Mσs 时基本不再呈现双程记忆效应。马氏体再取向形成的位错可以产生有效内应力场 ,诱发双程形状记忆效应     

NiMnGa合金磁控形状记忆效应及外特性

系统地阐述了铁磁NiMnGa合金的微结构、相变机理、形状记忆效应，并对NiMnGa磁控形状记忆合金的外特性进行了实验研究，得出了磁场、温度、预压力与NiMnGa合金形变率之间的静态关系，绘制了不同温度和预压力下的动态曲线，得比了静态形变率和动态形变率的变化规律。实验结果证明，NiMnGa合金变形率随预压力的增大而减小；随磁场强度的增大而增大；当温度接近向奥氏体转变温度时，形变率最大；这为NiMnGa合金的实际应用打下了理论和实验基础。     

Fe-Mn-Si多晶合金的形状记忆效应

本文研究了Fe-Mn-Si多晶合金的形状记忆效应(SME)与淬火温度的关系,以及马氏体转变点的变化。发现热轧样品经600—800℃处理后,记忆效应显著提高。形状记忆效应不仅受到ε相形态分布的影响,还与预存ε相的多寡有关。     

TRANSFORMATION CHARACTERISTIC OF TWO WAY SHAPE MEMORY MATERIAL CONSTRAINED BY STRESS

The snap-acting transition and two way shape memory (TWSM) effect have been obtainedin a TWSM spring made of Ni51Ti49 alloy using the constrained effect of stress on drivingforce of TWSM material.When the snap-acting transition has been realized:M_s= M_f andA_s=A_f;hysteresis is rectangular,the height (TWSM effect) and width (hysteresis) of therectangle can be readjusted by means of constrained stress.The results of resistancemeasurments show that,the snap-acting TWSM effect mentioned above was supplied mainlyfrom the transformation of P←→R.The thermodynamic model has also been proposed to ac-count for the snap-acting transformation.     

DSC ANALYSIS OF A CuZnAl TWO WAY SHAPE MEMORY ALLOY DURING AGEING

ＤＳＣＡＮＡＬＹＳＩＳＯＦＡＣｕＺｎＡｌＴＷＯＷＡＹＳＨＡＰＥＭＥＭＯＲＹＡＬＬＯＹＤＵＲＩＮＧＡＧＥＩＮＧ①ＺｈａｎｇＪｉａｎｘｉｎ，ＣａｉＷｅｉ，ＺｈａｏＬｉａｎｃｈｅｎｇＳｃｈｏｏｌｏｆＭａｔｅｒｉａｌｓＳｃｉｅｎｃｅａｎｄＥｎｇｉｎｅｒｉｎｇ...     

TWO KINDS OF VARIANT IN SHAPE MEMORY MATERIAL

In shape memory materials,that have been trained to have a two way shape memory effect(TWSM),themartensitic variants are classified into two groups,i.e.,preferentially oriented variants and self-accommodatingvariants.Applied stress may promote or constrain the transition of preferentially oriented variants and so changetransformation temperatures but has no essential effect on self-accommodating variants.According to the pointof view mentioned above,some experimental phenomena during thermocycling of a TWSM device may be ex-plained,such as the absence of synchronization between the plot of resistance change.temperature and the plotof memory strain vs.temperature.     

单向,双向记忆合金的相变热测定

用ＤＳＣ－７研究了ＣｕＺｎＡｌ单向，双向记忆合金相变潜热，发现：单向，双向记忆合金相变过程的ＤＳＣ曲线形状各异，单向记忆合金的ＤＳＣ曲线为犬牙状，有多个峰；而双向记忆合金的ＤＳＣ曲线只有一个峰。在相变大小上，单向记忆合金的相变热比双向记忆合金约大１／４。     

DESIGN CONCEPT FOR SNAP-ACTING TWO-WAY SHAPE MEMORY DEVICES

Snap-acting two way shape memory device can be obtained by using the design proposed byauthors.Some essential parameters which characterize the properties of device have been pro-posed also in this paper.And the principle and method according to which a practicalsnap-acting device can be designed have been described.     

SNAP-ACTION PHASE TRANSFORMATION IN TWO-WAY SHAPE MEMORY Ni-Ti ALLOY

The snap-action behavior of a Ni-Ti alloy disc which is controlled by combination of anonlinear stress field and temperature has been studied.After treatment for two-way shapememory,all shape memory strain of snap-action finishes abruptly at a certain temperaturewithin an interval of less than 1 ms.The results of resistance measurement and in-situ X-raydiffraction indicate that the snap-action strain is mainly resulted from the snap-action β R transformation.     

Ni含量对TiNi形状记忆合金相变行为的影响

用示差扫描热分析仪和光学显微镜系统研究了Ｎｉ含量对ＴｉＮｉ形状记忆合金Ｒ相和Ｍ相相变温度，相变热，热滞的影响。结果表明：在加热和冷却过程中，Ｔｉ－３３．３％Ｎｉ和Ｔｉ－７５．０％Ｎｉ不发生相变；ＴＭ，ΔＭ，ΔＨＭ和ΔＨＲ是Ｎｉ是含量的函数，ＴＲ和ΔＲ基本为一定值，与Ｎｉ含量有关。     

Ni-Ti形状记忆合金中母相(?)马氏体可逆转变过程的研究SCIEI

用透射电镜对Ni-Ti形状记忆合金中母相?马氏体可逆转变进行了动态观察。利用高分辨电子显微术研究了该合金相变温度上下的结构变化。结果表明,马氏体与奥氏体的取向关系为:[111]_A∥[110]_M,[110]_A∥[001]_M,(110)_A∥(001)_M,(110)_A与(010)_M间夹角为6.5°左右;马氏体的晶体缺陷多为孪晶和层错,新发现有孪晶而为(100)的孪晶。     

REVERSIBLE TRANSFORMATION BETWEEN MATRIX AND MARTENSITE IN Ni-Ti SHAPE MEMORY ALLOYS

The reversible transformation between matrix and martensite in Ni-Ti shape memory alloyshas been dynamically observed under TEM.The orientation relation between martensite andaustenite as well as the structural change near the transition temperature has been also studiedwith the help of HREM SADP.The results show that the orientation relation betweenmartensite and austenite is[(?)11]_A//[(?)10]_M,[110]_A//[001]_M,(110)_A//(001)_M and theangle between((?)110)_A and(010)_M is about 6.5°.The crystal defects of martensite are foundto be twin and stacking fault,and the twin plane as(100).     

SHAPE MEMORY EFFECT OF POLYCRYSTALLINE Fe-Mn-Si ALLOYS

The influence of quenching temperature on the shape memory effect(SME)of theFe-Mn-Si polycrystalline alloys and their martensitic transformation temperature have beenstudied.The SME of the hot-rolled specimen may be remarkably enhanced by selectingquenching temperature of 600—800℃.It has been shown that SME is influenced not only bythe distribution of ε-phase morphology but also by its pre-existence.