Temperature memory effect of Ti50Ni30Cu20 (at.%) alloy

After the reverse thermal induced martensitic transformation process of shape memory alloy is arrested at a temperature between the reverse transformation start and finish temperatures (A_s and A_f), and then cooled to a temperature below M_f, a kinetic stop will occur in the next heat flow curve during the heating process. The kinetic stop is closely related to the arrested temperature. This phenomenon is called temperature memory effect (TME). TME of Ti₅₀Ni₃₀Cu₂₀ (at.%) shape memory alloy with phase transformation between B2 austenite and B19 martensite has been investigated by differential scanning calorimeter in this paper. The results indicate that TME of Ti₅₀Ni₃₀Cu₂₀ alloy only exists in the heating process.     

TiNiCu形状记忆合金薄带研究进展

TiNiCu形状记忆合金薄带凭借其窄相变滞后、优异的形状记忆效应与超弹性、良好的热循环稳定性成为一种很有前途的微驱动器材料。本文全面阐述了国内外在TiNiCu薄带研究方面的最新进展,主要包括晶化行为、显微组织、马氏体相变行为、形状记忆效应与超弹性,重点介绍了热处理工艺-显微组织-性能之间的内在联系,探讨了TiNiCu薄带今后的研究重点     

退火温度对淬火态Fe-Mn-Si-Cr-Ni合金记忆效应的影响

研究了退火温度对淬火态预先存在热诱发ε马氏体的Fe-14Mn-5.5Si-8.0Cr-5.0Ni合金和无热诱发ε马氏体的Fe-19Mn-5.0Si-8.0Cr-6.0Ni合金记忆效应的影响。结果表明:预先存在热马氏体合金的形状回复率随退火温度的升高,先上升后下降,在500℃附近达到最大值。但无热马氏体存在合金的形状回复率随退火温度的变化却相反,在500℃附近达到最小值;两种合金的Ms温度都随退火温度的升高而下降,在500℃附近达到最低。预先存在热马氏体的合金由于退火后Ms温度的降低,减少了热诱发的马氏体量,因而形状记忆效应得到了提高;而无热马氏体存在的合金由于退火后Ms温度的进一步下降,使得应力诱发马氏体转变更不容易发生,因此形状记忆效应反而下降。     

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。     

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。     

不同Cu含量的TiNiCu形状记忆合金薄膜的组织与相变

利用TEM、XRD、DSC测试方法,首次系统地研究了直流磁控溅射制备的3种不同Cu含量的TiNiCu形状记忆合金薄膜的退火组织和加热与冷却过程中发生的相变.结果表明:退火后的薄膜获得了形状记忆性能;随着薄膜中Cu含量的增加,薄膜的退火组织出现差异,相变滞后明显变小,相变温区变窄;使获得快速响应的形状记忆合金薄膜成为可能.     

退火态Ti-49.8Ni形状记忆合金的组织及性能研究

用光学显微技术及拉伸试验研究了退火温度T_a和形变温度T_d对Ti-49.8Ni(原子分数,%)形状记忆合金(SMA)丝材及弹簧的显微组织与形状记忆行为的影响.结果表明:冷加工态Ti-49.8Ni合金组织呈纤维状;退火后,随T_a升高,其显微组织逐渐从纤维状向等轴状过渡,合金丝和弹簧的马氏体(M)再取向力先减小后增大;退火态合金在室温下呈形状记忆效应,随T_d升高,合金的M再取向力升高,形状记忆效应份额逐渐减少,超弹性效应份额逐渐增加.     

Ti（50）Ni（47）Fe3形状记忆合金冷轧变形后的组织与性能

采用拉伸测试、维氏硬度测试、电阻率-温度曲线测试及扫描电镜和透射电镜观察显微组织的方法研究冷轧变形量为25%的Ti50Ni47Fe3合金经450-750°C下1 h退火后的显微组织和性能。结果表明,冷轧变形增强了合金的抗拉强度和屈服强度,冷轧变形后形成的应力场有助于R相变的发生。随着退火温度的升高,合金的抗拉强度和屈服强度下降,伸长率增大;当退火温度高于650°C时,强度和伸长率趋于稳定。电阻-温度曲线表明,在升、降温过程中发生两阶段相变B2-R-B19′。随着退火温度的升高,合金的相变温度降低;当退火温度高于650°C时,相变温度趋于稳定。随着退火温度的升高,合金依次发生回复、再结晶和晶粒长大。     

Modeling of effects of matrix on actuation characteristics of embedded shape memory alloy wires

1 INTRODUCTIONOne major application field of shape memoryalloys(SMAs) is the so-called smart structures .Numerous researches have been done on the actua-tion abilities of SMAs ,andthe results are quitein-spiring[1 ,2]. However , the complicated behaviorsof SMAs are still not fully understood, which pre-vents SMAs frombeing further adopted in real in-dustrial structures . The difficulties in understand-ing the SMAs mainly come fromthe fact that thetransformation and thus the actuatio…     

Ti49.4Ni50.6超弹性弹簧的相变和形变特性

用示差扫描量热仪、拉伸实验和应力-应变循环实验系统研究了退火温度、变形温度以及热循环和室温应力-应变循环对Ti49．4Ni50．6超弹性(SE)弹簧的相变和形变特性的影响。冷加工加中温退火态Ti49．4Ni50．6合金冷却→←加热时的相变类型为母相B2→←R相→←马氏体B19′。随退火温度升高，马氏体转变温度升高，R相转变温度降低。623-773K退火态Ti49．4Ni50．6弹簧室温下可获得SE特性，随变形温度升高，SE弹簧剐度增加；当退火温度超过823K后，SE持性变差。热循环时SE弹簧的切变量取值越小，其应变恢复率越高。预循环训练可增强SE的稳定性。     

退火处理对NiTi记忆合金丝力学性能的影响

以德国Memory-Metalle有限公司生产的两种型号NiTi合金丝为研究对象,其一是具有中温激励特性的M型,其二是具有超弹性的N型,通过拉伸实验,研究了退火处理对其力学性能的影响.结果表明:不同的退火温度和退火时间对试样的形状记忆性能以及超弹性具有不同程度的影响.     

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 annealing and heating/cooling rate on the transformation temperatures of NiFeGa alloy

In this work, Ni₅₅Fe₁₈Ga₂₇ ferromagnetic shape memory alloy was prepared through a suck-casting method. The effects of annealing and heating/cooling rate on the martensitic transformation temperatures were investigated by differential scanning calorimetry (DSC). The results showed that the phase transformation temperatures increase with increasing the annealing temperature, upon the heating and cooling process. However, the start and the finish temperatures (M_s and M_f) of martensitic phase transformation increased firstly and then decreased upon the cooling process with the increase the annealing time at 300 °C. The start and the finish temperatures (A_s and A_f) of inverse phase transformation increased slightly upon the heating process with the increase of the annealing time. The results can be explained by the evolution of the microstructure after heat treatment. It was also found that the phase temperatures show great dependence on the heating/cooling rate of the DSC test, A_s and A_f increased and M_s and M_f decreased with the increase of the heating/cooling rate.     

Effect of Annealing Temperature on the Shape Memory Properties of Cold-Rolled Dual-Phase Ni-Mn-Ga-Gd Alloy

The influence of annealing temperature on the shape memory effect (SME) and recovery ratio of cold-rolled dual-phase Ni₅₈Mn₂₅Ga_16.9Gd_0.1 high-temperature shape memory alloy were investigated. The results showed that the SME can be improved by appropriate annealing. SME of 6.0% and recovery ratio of 98% were observed in the rolled alloy at 550 °C annealing, which were larger than that of the samples annealed at other temperatures. The annealing temperature was in between the recrystallization temperatures of the martensite and γ phase, which leads to the work-hardening state of γ phase kept unchanged during annealing process, and therefore, the critical slip stress of γ phase increased. Thus, the plastic deformation of γ phase reduced during the compression process, and the SME increased.     

Ti-Ni-V形状记忆合金及其弹簧的相变和形变特性

用X射线衍射仪、示差扫描量热仪和拉伸实验研究了退火温度Tan和形变温度Td对Ti-50.8Ni-0.5V形状记忆合金丝及其弹簧的相变和形变特性的影响。结果表明:400～600℃退火态合金的室温相组成为B2和R相。冷却/加热时,350～400℃退火态合金发生A→R/R→A(A—母相,R—R相)一阶段可逆相变;450～500℃退火态合金发生A→R→M/M→R→A(M—马氏体相)两阶段可逆相变;550℃退火态合金发生A→R→M/M→A型相变;600℃退火态合金发生A→M/M→A一阶段可逆相变。随Tan升高,R相变温度先升高后降低,M相变温度先升高后趋于稳定,M相变热滞快速降低,而R相变热滞则几乎不受退火温度影响。随Td和Tan升高,退火态Ti-50.8Ni-0.5V合金弹簧的应力诱发M临界切应力升高。     

TiNi合金不完全相变的温度记忆效应

通过示差扫描量热分析(DSC)研究了预应变及约束条件下TiNi形状记忆合金的温度记忆效应．结果表明，通过变形约束手段，可以大大拓宽TiNi合金的相变温度区间，使得TiNi合金的温度记忆效应能够在一个非常大的温度范围内发挥作用；同时，变形并约束后TiNi合金的温度记忆效应比自由态TiNi合金的温度记忆效应更加准确．分析表明，马氏体与母相界面处的位错以及界面处的弹性自适应过程是可能的温度记忆效应机制。     

EFFECT OF HEAT TREATMENTS ON THE MICROSTRUCTURE AND TRANSFORMATION CHARACTERISTICS OF TiNiPd SHAPE MEMORY ALLOY THIN FILMS

Microstructure and phase transformation behaviors of the film annealed at different temperatures were studied by X-ray diffractometry （XRD）, transmission electron microscopy and differential scanning calorimeter （DSC）. Also tensile tests were examined. For increasing annealed temperature, multiple phase transformations, transformations via a B19-phase or direct martensite/austenite transformtion are observed. The TiNiPd thin film annealed at 750℃ had relatively uniform martensite/austenite transformtion and shape memory effect. Martensite/austenite transformtion was also found in strain-temperature curves. Subsequent annealing at 450℃ had minor effect on transformation temperatures of Ti-Ni-Pd thin films but resulted in more uniform transformation and improved shape memory effect.     

Transformation behavior and mechanical properties of a nanostructured Ti−50.0Ni(at.%) alloy

Transformation behavior, the shape memory effect and the superelasticity of an equiatomic 40% cold worked Ti−Ni alloy followed by annealing at various temperatures have been investigated by means of differential scanning calorimetry (DSC), transmission electron microscopy, thermal cycling tests under constant load and tensile tests. The B2-R-B19 transformation occurred in all samples, and the R-B19’ transformation occurred in a wide temperature range. The B2-R transformation start temperature kept constant with raising annealing temperature. The average grain size increased from 23 to 80 nm with raising annealing temperature from 523 to 673 K. Transformation hysteresis increased rapidly with raising annealing temperature up to 623 K, above which they almost keep constant, which was ascribed to the small grain size and large constraints of grain boundaries.     

热机械训练影响TiNiCu记忆合金DSC曲线特征的研究

利用示差扫描量热法(DSC)研究了加热伸长、冷却收缩和加热收缩、冷却伸长2种TiNiCu双向记忆效应弹簧训练过程中相变特征。研究结果表明，训练前升温时，DSC曲线表现出吸热峰由多个小峰组成，随着训练次数的增加，峰的个数减少，具有稳定双向记忆效应的试样中，升温时只出现1个锐利的峰。这是因为在训练过程中引入特定取向的位错，产生一定的应力场，使得马氏体变体的取向比较一致，相变点基本相同所导致。并由于位错的引入，引起相变点As和Af下降。     

退火温度对Ni47Ti44Nb9冷拉丝及热拉丝力学性能和记忆性能的影响

(In2Te3)x(SnTe)1-x系列化合物具有较低的电导率和热导率,热电性能较差.考虑到其中的In2Te3单元具有三分之一的阳离子空位,可以通过掺杂Cu等外来原子来占据In的空位,使化合物的载流子浓度达到最优化,降低材料的热导率从而改善其热电性能.本组实验中,采用真空熔炼、机械球磨及放电等离子烧结技术制备了(In2-xCuxTe3)0.08(SnT)0.92(x=0.025,0.05,0.2)系列化合物.测试结果表明,掺杂不同摩尔数的Cu元素后,材料的Seebeek 系数几乎没有变化,电导率有所提高,晶格热导率kL值大幅度降低,成功地抑制了高温区(In2Te3)0.08(SnTe)0.92的双极扩散效应.当x=0.2时,该化合物在647 K取得最大ZT值0.29,是掺杂Cu元素前ZT值的4.6倍.