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使用透射电镜(TEM),动态热机械分析(DMA)以及示差扫描量热法(DSC)等测试方法对固溶态25%冷变形Ti_(50)Ni_(45)Cu_5合金400℃/1 h,500℃/1 h,600℃/1 h,700℃/1 h退火态的组织结构,马氏体相变特征以及力学性能进行分析,并在实验中对比使用DSC与DMA两种测试方法用于马氏体相变测试。结果表明,随着退火温度升高,Ti50Ni45Cu5合金的强度、硬度降低,塑性升高,400℃/1 h退火态合金有最高的强度和硬度,分别为996 MPa和HV 280,700℃/1 h退火态合金有最好的延伸率27.8%。随着退火温度升高,合金的马氏体相变温度因为合金内位错密度降低,孪晶晶界减少及内应力减少,逐渐从54.5℃下降至37.7℃。400℃/1 h,500℃/1 h,700℃/1 h退火态合金均发生B19-B19’马氏体相变,而600℃/1 h退火态合金由于Ti3Ni4相的析出B2-B19’马氏体相变转变为B2-B19-B19’两步马氏体相变。两步马氏体相变的B2-B19相变部分和B19-B19’相变部分均在DMA模式测试出,而DSC模式只检测出B2-B19相变部分,DMA模式更适合于本实验测试马氏体相变。
The microstructures of 25% cold-deformed Ti 50 Ni 45 Cu 5 alloy at 400 ℃ for 1 h were investigated by transmission electron microscopy (TEM), dynamic thermomechanical analysis (DMA) and differential scanning calorimetry (DSC) 500 ℃ / 1 h, 600 ℃ / 1 h, 700 ℃ / 1 h annealed microstructure, martensitic transformation characteristics and mechanical properties were analyzed, and in the experiment using the DSC and DMA compared to the two test methods Martensitic transformation test. The results show that the strength and hardness of Ti50Ni45Cu5 alloy decrease with the increase of annealing temperature. The highest strength and hardness of Ti50Ni45Cu5 alloy annealed at 400 ℃ for 1 h are 996 MPa and HV 280 and 700 ℃ / 1 h respectively Alloy has the best elongation of 27.8%. With the increase of annealing temperature, the martensitic transformation temperature of the alloy gradually decreased from 54.5 ℃ to 37.7 ℃ because of the decrease of the dislocation density, the decrease of twin grain boundaries and the decrease of internal stress. B19-B19 ’martensitic transformation occurred in the annealed alloys at 400 ℃ / 1 h, 500 ℃ / 1 h and 700 ℃ / 1 h, respectively. However, the as-deposited Ti3Ni4 phase at 600 ℃ for 1 h precipitated B2-B19’ Martensitic transformation into B2-B19-B19 ’two-step martensitic transformation. The B2-B19 phase transition and the B19-B19 ’phase transition of the two-step martensitic transformation were both tested in the DMA mode while the DSC mode only detected the B2-B19 phase transition. The DMA mode was more suitable for this experiment Martensitic transformation.