钛镍形状记忆合金加热过程中的晶粒长大行为

Grain Growth Behavior of Ti-Ni Shape Memory Alloy in Heating Process

通过真空感应炉制备了Ti-50.9Ni(at%)形状记忆合金铸锭,经锻造、轧制及热拉拔至φ2.0 mm丝材。830℃退火后,对其进行42.4%变形量的冷拉拔,然后对冷拉拔后的钛镍合金丝材进行650~950℃加热并保温15~120 min。借助金相显微镜研究了加热温度和时间对Ti-50.9Ni形状记忆合金晶粒尺寸的影响,推导并验证了Ti-50.9Ni形状记忆合金加热过程的晶粒长大模型。结果表明:钛镍合金晶粒尺寸呈抛物线长大,加热温度越高,晶粒长大速率越快。钛镍合金在650~950℃加热时晶粒生长指数n=4.32,晶粒长大激活能Q=195.942 k J/mol,高于晶粒生长指数的理论值。使用建立的晶粒长大模型预测的晶粒尺寸与实测晶粒尺寸吻合良好。

Ti-50.9Ni （at%） shape memory alloy ingot was prepared by the vacuum induction furnace, and was changed into 4,2.0 mm wire after forging, rolling and hot drawing. After annealing at 830 ℃, the cold drawing with 42.4% deformations was carried out. After the cold drawing were the Ti-Ni alloy wires heated at 650-950 ℃ and insulated for 15-120min. The effects of heating temperature and holding time on the grain size of Ti-50.gNi shape memory alloy were researched by means of metallographic microscope. The grain growth model of Ti-50.9Ni shape memory alloy in heating process was deduced and verified. The results indicate that the grain size growth of Ti-Ni alloy is parabolic, the higher the heating temperature is, the faster the grain growth rate is. When the Ti-Ni alloy is heated at 650-950℃, the grain growth index is n =4.32, and the activation energy of the grain growth is Q=195.942 kJ/mol, which is higher than the theoretical value of the grain growth index. Grain size predicted by the established model of grain growth is in good agreement with the measured grain size.