快速凝固Ni-Ti形状记忆合金的全程记忆效应

【作者】 李海江；

【导师】 谢致薇；

【作者基本信息】 广东工业大学 ， 材料学， 2005， 硕士

【摘要】 本文采用快速凝固技术（铜模真空吸铸法）制得Ti-51at%Ni形状记忆合金,利用差示扫描量热法（DSC）、X射线衍射（XRD）和扫描电子显微镜（SEM）等现代检测手段对快凝制得的合金的相变及记忆性能、结构和组织进行相应的分析研究。并采用约束时效“训练”工艺来获取快凝Ti-51at%Ni形状记忆合金的全程形状记忆效应,讨论分析了快凝Ti-51at%Ni合金在训练时的显微组织的演化规律,进而研究了约束时效中不同的约束时效时间、约束时效温度对快凝合金全程形状记忆效应的影响。本文的研究结果表明: 1.快速凝固制得Ti—51at%Ni合金在升温过程中发生了二次相变,马氏体逆相变和R相逆相变发生了明显的分离,相变温度点As（Ms）显著降低。 2.快凝Ti—51at%Ni合金形成以超细晶粒为特征的显微组织,基体为从合金铸件两表面向中间生长的双柱状晶,基体中有强织构现象存在,在室温下为典型CsCl型B2结构;合金中没有全程形状记忆效应或双程形状记忆效应,但其单程形状记忆效应非常明显:回复率大,响应速度快。 3.合金经过约束时效处理,在300℃下呈现了双程形状记忆效应;在400℃下随时效时间的延长逐步由双程形状记忆效应向全程形状记忆效应转变;在500℃下,出现了不同程度的全程形状记忆效应,随着时效时间的延长,全程形状记忆效应在500℃1h达到一个最佳值后又逐步地减弱;在600℃下,不同的时效时间均没有自发的形状变化,仅出现单程形状记忆效应。 4.快凝工艺制得的合金经过约束时效处理后在全程形状记忆效应的实现过程中发生了二次相变:R相变和马氏体相变。约束时效时间和约束时效温度的改变对马氏体相变有明显的影响,而对R相变没有明显影响。 5.约束时效后的样品主要是由CsCl型母相（B2）和析出相Ti₃Ni₄组成,此外含有少量的马氏体相。合金的基体结构没有发生大的变化。约束时效温度的升高和约束时效时间的延长均有助于析出相Ti₃Ni₄的析出和长大。合金中的全程形状记忆效应是否实现主要取决于其析出相Ti₃Ni₄,与Ti₃Ni₄相的数量（和形貌）有很大的关联。更多还原

【Abstract】 In this paper, Ti-51at%Ni shape memory alloys（SMAs） were prepared by means of Rapid Solidification Technology （copper-mold vacuum suction casting） and shape memory effect and microstructure were investigated by differential scanning calorimeter（DSC）, X-ray diffraction（XRD）, scanning electron microscope（SEM）, etc. Constrained aging "training" method was used to obtain the All-round way shape memory effect（ARSME） of Ti-51at%Ni SMAs. The change of microstructure and the influence of constrained aging temperature and time on ARSME during constrained aging process were investigated. The results show:1. There are two transformations（reverse martensitic transformation and reverse R-phase transformation） in Ti-51at%Ni SMA during the heating process, which are separated each other. As（Ms） decrease sharply.2. The microstructure of Ti-51at%Ni SMA is characteristic of super-fine grain and two-columnar crystal which growed from the alloy’s surface to center. Intensive-texture is found in alloy. There is B2 （typical CsCl type） structure in the substrate in room temperature. There are not ARSME and TWSME in alloy.There is sharp OWSME with big recovery rate and high respondence in alloy.3. There is TWSME in the alloy After 300℃ constrained aging; Gradual change form TWSME to ARSME as aging time increases occurs after 400 ℃ aging; There are different ARSMEs after 500 ℃ aging, which depends on aging time and increases first and then decreases as the aging time increases; There is only OWSME after 600℃ aging.4. There are two transformations in ARSME after constrained aging treatment: martensitic transformation and R-phase transformation. Constrained aging temperature and time have remarkable influence on martensitic transformation, but there is little effect on R-phase transformation.5. The alloy consists of parent B2、 Ti₃Ni₄ phase and few martensite-phase after constrained aging treatment and its structure has not distinctive change. The更多还原