Ti-51.8at%Ni形状记忆合金中Ti_3Ni_4相的析出过程

 用透射电镜系统地研究了Ti-51.8at％Ni形状记忆合金在300～600℃时效时Ti_3Ni_4相的析出过程。结果表明:Ti_3Ni_4相以均匀成核方式从过饱和基体中弥散析出。时效初期,Ti_3Ni_4相为细小颗粒状;随时效时间延长或时效温度升高,Ti_3Ni_4相逐渐长大为透镜片状,最终粗化为粗片状。Ti_3Ni_4相通常与基体保持良好的共格关系,其共格应变场衬度随Ti_3Ni_4相尺寸增大而变化,至Ti_3Ni_4相聚集粗化后,与基体的共格关系逐渐丧失,并在其周围基体中产生位错,位错的柏氏矢量为1/2(111)_(B2)或1/2(111)_(B2)。

PRECIPITATION PROCESS OF Ti_3Ni_4 PHASE IN Ti-51.8at%Ni SHAPE MEMORY ALLOY

The precipitation processes of Ti3Ni4 phase in Ti-51.8at% Ni alloy aged at 300 ~ 600℃ have been systematically studied by means of transmission electron microscope. It is found that the Ti3Ni4 precipitates nucleate homogeneously at the early stage of aging and appeal as fine dispersed particles . Upon the prolongation of aging time or temperature , the Ti3Ni4 precipitates become gradually the lenticular-like shape , and finally exhibit coarse plates. They are in good Coherence with the matrix. The contrast of the internal strain fields caused by the coherent Ti3Ni4 precipitates changes with their growth. When the Ti3Ni4 precpitates are coarsened enough, they lost in coherence with the matrix and produce dislocations about them . The Bagle's vectors for these dislocations are determined to be 1 / 2111]B2 or 1 / 2111]B2.