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用水冷铜模吸铸法制备Ti86.5Nb7.5Mo4Sn2(at%,下同)合金,将合金在室温下进行了冷轧(变形量为80%),然后在973 K,不同保温时间下对合金进行了退火。研究了退火时间对合金显微组织及其超弹性的影响。结果表明,冷轧后得到了晶粒细长的变形组织,该组织在973 K下固溶处理后发生了再结晶,形成了细小的等轴晶粒组织。冷轧后的合金组织主要由β相以及少量的α′′相组成,而固溶后的合金组织主要由β相以及少量的α相和α′′相组成。随着固溶时间延长,合金的晶粒尺寸逐渐增大。固溶处理后的合金在室温下表现出超弹性,其马氏体诱发临界应力σSIM与晶粒尺寸的关系满足Hall-Petch方程。因此,减小合金晶粒尺寸,可有效提高合金的超弹性性能。
Ti86.5Nb7.5Mo4Sn2 (at%, the same below) alloy was prepared by water-cooled copper die-casting method, the alloy was cold rolled at room temperature (deformation amount of 80%) and then alloyed at 973 K for different holding time Annealed. The effect of annealing time on the microstructure and superelasticity of the alloy was studied. The results show that after the cold rolling, the elongated and deformed microstructure of the grain is obtained. The microstructure recrystallizes after solution treatment at 973 K, forming fine equiaxed grain structure. The cold-rolled alloy is mainly composed of β phase and a small amount of α “phase, while the solid solution alloy structure mainly consists of β phase and a small amount of α phase and α” phase. As the solution time increases, the grain size of the alloy gradually increases. The solution treated alloys showed superelasticity at room temperature. The martensite-induced critical stress σSIM and the grain size satisfy the Hall-Petch equation. Therefore, reducing the alloy grain size can effectively improve the superelastic properties of the alloy.