纯铂的热塑性变形行为及微观结构演变规律研究

用热模拟试验机研究了纯铂在真应变量为0.9、变形温度为550℃～950℃和应变速率为0.01～1 s~(-1)的热塑性变形行为,并对热压缩后的样品进行了金相观察和显微硬度测量。结果表明,纯铂的流变应力随变形温度的升高和应变速率的降低而降低;其热压缩变形过程中软化行为由变形温度和变形速率共同作用决定,一般以动态回复为主,而在低应变速率和高形变温度下以动态再结晶为主,动态再结晶发生造成的软化使纯铂样品的硬度迅速下降。利用Zener-Hollomon参数方程获得了热塑性变形流变应力本构方程,得到纯铂的热变形激活能为208.51 kJ/mol,流变应力拟合公式计算值与实验值的平均误差为5.9%。

Study on the hot plastic deformation behavior and microstructure of pure Pt

The hot thermoplastic deformation behavior of pure Pt was studied by a thermal simulator at a true strain of 0.9, a deformation temperature of 550°C~950°C and a strain rate of 0.01~1 s^-1. Its microstructure was observed by metallographic microscope and its microhardness was measured after the hot compression experiment. The results showed that the flow stress of pure Pt decreased with the increase of deformation temperature and decrease of strain rate. During the process of hot compression deformation, the softening behavior of pure Pt was determined by the combination effect of deformation temperature and strain rate. Dynamic recovery was generally dominated, while dynamic recrystallization dominated at low strain rate and high deformation temperature. The softening caused by dynamic recrystallization resulted in the rapid decrease of microhardness. Using Zener-Hollomon parameter equation to obtain the thermoplastic deformation flow stress constitutive equation, and the obtained thermal deformation activation energy of pure Pt was 208.51 kJ/mol. The average error of flow stress between fitting and experimental values was 5.9%.