热处理对形状记忆合金TiNi相变的影响

Effect of heat treatment on phase transformation of shape memory alloy TiNi

为了研究形状记忆合金TiNi的热处理工艺对其相变的影响,本文对冷成型后的Ni含量为55.6 at.%TiNi合金,采用在不同温度保温0.5 h,出炉后空冷的热处理工艺,然后通过示差扫描量热仪分析热处理后样品的相变,相变转变温度,转变热焓与热处理温度之间的关系。结果显示:当热处理温度小于425℃,在DSC升温过程中发生了M相向A相转变,相变开始点温度随着热处理温度的升高而升高,转变热焓随着热处理温度升高而下降;在425℃至500℃之间热处理的样品,在DSC升温过程中发生了M相向R相转变,然后再向A相转变,相变开始点温度随着热处理温度的升高,先升高,在425~445℃达到峰值,随后开始下降,转变热焓随着热处理温度升高而升高;高于500℃热处理的样品,在DSC升温过程中发生M相向A相转变,相变开始点温度和转变热焓随着热处理温度升高而下降。

In order to study the effect of heat treatment process of shape memory alloy TiNi on its phase transformation, the TiNi alloy wire with a Ni content of 55.6 at.% was cold formed.The as-cold formed TiNi alloy was kept at different temperatures for 0.5 h in the furnace, and then was subjected to air cooling.The differential scanning calorimeter was used to analyze the relationship between the phase transformation, phase transformation temperature, transformation enthalpy and heat treatment temperature of the as-cold formed sample.When the heat treatment temperature was less than 425 ℃,M phase transformed to A phase during DSC heating;The phase transformation starting point temperature increased with the increase of heat treatment temperature;The enthalpy of transition decreased with the increase of heat treatment temperature.For the samples heat-treated between 425 ℃ and 500 ℃,during DSC heating, M phase transformed to R phase, and then to A phase;With the increase of heat treatment temperature, the temperature of the phase transformation starting point first rose, reached the peak at 425-445 ℃,and then began to decline;The transition enthalpy increased with the increase of heat treatment temperature.For the samples heat-treated above 500 ℃,M phase transformed to A phase during DSC heating, and both the temperature of the phase transition starting point and the enthalpy of transformation decreased with the increase of heat treatment temperature.