时效近等原子比钛镍形状记忆合金TEM分析

应用TEM分析技术对一种富Ni钛镍形状记忆合金时效后的组织进行了研究 ,结果表明 ,在不同温度下时效析出物的相结构和形态是不同的 .在 6 73～ 773K温度时 ,析出物都是Ti1 1 Ni1 4 相 ,随时效温度的提高 ,析出物的形态由细点状变为透镜状截面的椭圆板 ,这种相与B2母相是共格的 ,它的应变场使R相变与马氏体相变分离 ,Ti1 1 Ni1 4 相的析出会改善钛镍形状记忆合金的性质 .此外 ,在更高温度下时效合金将析出稳定的TiNi3相 ,该相与基体没有共格关系 ,同时导致基体镍含量下降 ,提高了马氏体转变温度 .

TEM Analysis of Aged Near-Equiatomic Titanium Nickelide Shape Memory Alloy

The paper studies the structure of an aged Ni rich TiNi shape memory alloy in term of transmission electron microscopy (TEM). As a result, Ti 11 Ni 14 phases are precipitated in the alloy after aging at 673-773?K. With the increase of aging temperature, the morphology of the precipitates changes from small points into oval plates with lenticular sections.These precipitates are coherent with the parent B 2 phase. Its strain field makes R transformation separated from martensitic transformation. Ti 11 Ni 14 precipitates can improve the properties of TiNi shape memory alloys. Moreover, aging at higher temperature leads to precipitating of stable TiNi 3 phases,which have no coherent relation with the matrix. The decrease of Ni content caused by this kind of precipitation increases the martensitic transformation temperature.