激冷Ti-47Ni合金薄带的组织、相变和形状记忆行为

Microstructure,Phase Transformation and Shape Memory Behavior of Chilled Ti-47Ni Alloy Ribbons

为了开发微机电系统用快响应微执行器材料,采用熔体快淬法制备了激冷Ti-47Ni(原子分数,%)形状记忆合金薄带,利用CLSM、XRD、DSC和弯曲实验研究了铜辊速率和退火工艺对Ti-47Ni合金薄带显微组织、相组成、相变行为和形状记忆行为的影响。结果表明,不同辊速制备的铸态和300~800℃退火态Ti-47Ni合金薄带的显微组织均呈纵横排列的柱状,辊速越高合金薄带的晶粒越细,退火工艺对合金薄带显微组织影响不大。Ti-47Ni合金薄带的组成相为马氏体(B19'相,单斜结构)+母相(B2相,Cs Cl型结构),冷却/加热时发生B2→B19'/B19'→B2一阶段马氏体相变,正、逆马氏体相变温度分别约为54和81℃,相变热滞约为27℃。随辊速增加,合金薄带马氏体相变温度降低,形状记忆恢复率提高。随退火温度升高,合金薄带相变行为变化不大,形状记忆恢复率在93%~98%之间变化。铸态和退火态Ti-47Ni合金薄带皆具有优异的形状记忆效应。

The micro-actuater materials are needed urgently in micro-electro-mechanical systems（MEMS） which are developing rapidly. The melt-spun Ti-Ni shape memory alloy ribbons have become candidate materials since their fast heat response and large acting density. The bulk Ti-47 Ni（atom fraction, %） shape memory alloy is an ideal material to make thermosensitive actuators since its one-stage martensitic transformation and small temperature hysteresis. In order to develop the micro-actuator materials with fast response using in MEMS, the chilled Ti-47 Ni alloy ribbons were fabricated by melt-spinning in this research. The effects of the roller speed and the annealing processes on microstructure, phase composition, phase transformation behaviors and shape memory effect of Ti-47 Ni alloy ribbons were investigated by CLSM, XRD, DSC and bending test. The results show that the microstructure of as-cast and 300~800 ℃ annealed Ti-47 Ni alloy ribbons fabricated under different roller speeds is vertically and horizontally arrayed columnar. The higher the roller speed, the finer the grain is. The annealing processes do nearly affect the microstructure of the alloy ribbons. The composition phases of Ti-47 Ni alloy ribbons are martensite（B19＇ phase, monoclinic structure） and parent phase（B2 phase, Cs Cl-type structure）. The B2→B19＇/B19＇ →B2 type one-stage martensitic transformation occurs in Ti-47 Ni alloy ribbons upon cooling and heating, the martensitic transformation temperature and the reverse martensitic transformation temperature are about 54 and 81 ℃, respectively, and the temperature hysteresis is about27 ℃. With increasing the roller speed, the martensitic transformation temperatures of the alloy ribbons decrease, and the recovery rate of shape memory of the alloy ribbons increases. With increasing the annealing temperature, the transformation behaviors of the alloy ribbons change a little, and the recovery rate of shape memory changes in the range of 93% ~98%. The as-cast and annealed Ti-47 Ni alloy ribbons are all of excellent shape memory effect.