材料期刊网

用示差扫描量热仪(DSC)和部分热循环分析法研究了350—800 ℃退火态和300—500℃时效态Ti-(50.2—50.8)Ni(原子分数, %)形状记忆合金多阶段可逆相变的类型及其演化过程. 结果表明, 这些合金发生R和马氏体两种可逆相变, 相变可以一阶段完成, 也可以多阶段完成. 时效态合金的相变比退火态复杂, 时效温度越低相变越复杂. 若用DSC曲线上冷却相变峰数/加热相变峰数表示相变类型, 则退火态和时效态合金冷却/加热时可以发生1/1, 2/1, 2/2,3/2和3/3等类型的相变. 给出了各类相变发生的热处理工艺. 多阶段可逆相变是一个渐变过程, 在冷却相变峰的温度区间进行部分热循环时, 随冷却停止(加热开始)温度降低, 逆相变峰温度降低.

The multi-stage reversible transformation types and their evolving processes of Ti-Ni base shape memory alloys (SMAs) under various heat treatment processes have been investigated by differential scanning calorimetry (DSC) with partial thermal cycling method. The Ti-Ni base SMAs show many kinds of multi-stage reversible transformation types after various heat treatment processes. If expresses transformation type with peak numbers of cooling transformation / peak numbers of heating transformation on DSC curves, the 2/1, 2/2 and 3/2 type transformations occur upon cooling and heating in 350-550℃ annealed alloys; the 1/1 type transformation occurs when the annealed temperature is high than 600℃; the 3/2 and 3/3 type transformations occur in 300℃ aged alloys; the 2/2 type transformation occurs in 400℃ aged alloys; the 2/1 type transformation occurs in 500℃ aged alloys. The multi-stage reversible transformation is a gradually changing process. When partial thermal cycling was carried out within the temperature range of cooling transformation, the transformation temperature of reverse transformation decreases with decreasing thermal cycling start temperature.