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在不同温区及速率下,对Ni Ti形状记忆合金进行了动态冲击试验研究。利用X射线衍射、差示扫描量热仪和高分辨率透射电镜等手段探讨了冲击前后样品的物相转变和微观组织演化。结果显示:在冲击后的样品XRD曲线中,马氏体d值变大,表明Ni Ti合金样品在冲击过程中受到了拉应力作用。样品在受到低速冲击时,不同的冲击温度将会导致不同的物相转变机制,而当Ni Ti合金样品受到高速冲击时,则会触发马氏体解孪晶过程。
Dynamic impact test of Ni Ti shape memory alloy was carried out at different temperature and rate. The phase transformation and microstructure evolution of the samples before and after impact were investigated by means of X-ray diffraction, differential scanning calorimetry and high-resolution transmission electron microscopy. The results show that in the XRD curve of the sample after impact, the value of martensite d becomes larger, indicating that the sample of Ni Ti alloy is subjected to tensile stress during impact. When the sample is subjected to a low velocity impact, different impact temperatures will result in different phase transformation mechanisms. When Ni Ti alloy specimens are subjected to high velocity impact, the martensitic twinning process will be triggered.