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形状记忆合金的相变和力学性能受机械加工过程影响明显。在850℃下将Ti50Ni50-xAlx(x=1,2,4)形状记忆合金轧制成为板材。采用扫描电镜、透射电镜和X射线衍射对合金的微观结构研究表明:合金由NiTi相和Ti2Ni相组成,Al元素在Ti2Ni相中的固溶度比在TiNi相中高。差示扫描量热分析和电阻-温度测试表明:随着Al元素原子分数的增加,合金R相变和马氏体相变温度均下降,而两个相变之间的温度差增大。经850℃轧制以后,合金中Ti2Ni相减少,NiTi相中Al元素增加,从而使合金R相变和马氏体相变温度进一步降低,两个相变之间的温度差进一步增加,同时提高了合金的室温塑性。
The phase transformation and mechanical properties of shape memory alloys are significantly affected by the machining process. The Ti50Ni50-xAlx (x = 1, 2, 4) shape memory alloy was rolled into a sheet at 850 ° C. The microstructure of the alloy was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results show that the alloy consists of NiTi phase and Ti2Ni phase, and the Al content in Ti2Ni phase is higher than that in TiNi phase. Differential scanning calorimetry and resistance-temperature measurements show that the R-phase and the martensitic transformation temperature decrease with increasing Al atomic fraction, while the temperature difference between the two phase transitions increases. After rolling at 850 ℃, the Ti2Ni phase decreases and the Al element increases in the NiTi phase, so the phase transformation temperature and the martensitic transformation temperature of the alloy decrease further, and the temperature difference between the two phase transitions further increases and simultaneously increases The room temperature plasticity of the alloy.