热处理工艺对累积叠轧Ti/Ni多层复合材料界面结构的影响

Effect of Heat Treatment on the Interfacial Microstrucrure of Ti/Ni Multi-layered Composites

摘要:

本文研究了热处理对累积叠轧6道次Ti/Ni多层复合箔材界面结构演变的影响。利用扫描电镜(SEM)、能谱分析(EDS)、透射电镜(TEM)、X射线衍射(XRD)及差示扫描量热分析(DSC)对热处理后复合材料的界面结构、相组成、相结构及相变温度等进行测试分析。结果表明：随保温时间的增加,Ti/Ni界面扩散形成的不稳定化合物向稳定态转变,界面Ti、Ni两元素成分曲线由交叉陡变的阶梯状逐渐转为两条近平直的平行线。富Ti的Ti/Ni复合箔材在720℃经热处理后,随时间延长,材料组织从原始的层状结构最终转变为由稳态TiNi和Ti₂Ni两相组成的混合组织。保温时间小于10h时,材料中的TiNi是由具有复杂单斜结构的B19’和CsCl型结构的B2两种物相组成,大于10h时仅存在B19’相。在冷却/加热过程中,材料内部均发生马氏体(A→M/M→A)的可逆相变,并随保温时间的增加,其相变滞后(Ap-Mp)从1h的22.4℃增加到30h的31.9℃。

Abstract:

The interface evolution of Ti/Ni multi-layered composites produced by 6 cycles accumulative roll bonding after heat treatment was investigated in this study. And the interfacial structural, chemical composition and phase transition temperature of Ti/Ni multi-layered composites with different heat treatment were studied by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) and a differential scanning calorimeter (DSC). With the annealing time increased, the compounds formed by Ti/Ni interface diffusion transformed from unstable state to stable state, and the composition curves of Ti and Ni elements in the interface gradually change from a cross-steep ladder to two nearly straight parallel lines. With time increases, the microstructure of Ti-rich Ti/Ni composites treated at 720℃ transforming from a regular layered structure to a mixture structure with alternating TiNi and Ti₂Ni layers. When the hold time is less than 10h, the structure of TiNi phase is composed of B19" with complex monoclinal structure and B2 with CsCl structure, while when the time is more than 10h, only B19" phase exists. In the process of cooling/heating, a good martensitic and reversible phase transition of A→M/M→A occurred in each sample. With the increase of time, the phase transition hysteresis (Ap-Mp) from 22.4 ℃ of the 1 h heat treatment sample increases to 31.9 ℃ of the 30 h sample.