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为了探索冷却速度对镍钛形状记忆合金相变行为和组织的影响,通过差热扫描、X射线衍射、扫描电镜、X射线荧光分析等方法研究Ti-50.9%Ni(摩尔分数)合金的热处理。结果表明:当冷却速度非常低时(如炉冷)可诱发三级相变的产生;冷却速度对相变温度也有很大的影响,Ms和Mf都随冷却速度的降低而下降,降低冷却速度有利于提高M→A奥氏体相变温度,相变滞后宽度(Af–Mf)随着冷却速度的降低而增大;热处理不能消除镍钛合金热加工时所形成的织构,但能减弱其强度;冷却速度对晶粒大小影响不大。
In order to explore the effect of cooling rate on the phase transformation behavior and microstructure of NiTi shape memory alloy, the heat treatment of Ti-50.9% Ni (mole fraction) alloy was studied by differential scanning calorimetry, X-ray diffraction, scanning electron microscopy and X-ray fluorescence analysis. The results show that the third-order phase transformation can be induced when the cooling rate is very low (such as furnace cooling). The cooling rate also has a great influence on the phase transition temperature. Both Ms and Mf decrease with the decrease of the cooling rate, which decreases the cooling rate Which can help to improve the M → A austenite transformation temperature. The Af-Mf phase width increases with the decrease of cooling rate. The heat treatment can not eliminate the texture formed during hot working of NiTi alloy, Its strength; cooling rate has little effect on the grain size.