纯铌体材料的热压缩本构关系研究

Investigation on the Constitutive Relationship of Nb Bulk Materialsduring Hot Compression

摘要:

采用Gleeble-3500热模拟机测试了纯铌体材料的热压缩变形曲线,研究了200～700℃变形温度和0.001~10S_-1 应变速率条件下材料的流变应力行为和热压缩变形组织特征,结果表明：材料的流变应力随变形温度的升高和应变速率的降低而减小。随着变形温度的升高,材料中拉长的晶粒粗化,材料发生动态回复,材料的软化主要通过动态回复得以实现。进而通过修正的Arrhenius双曲正弦关系式,结合zener-Hollomon参数因子推导了材料应变速率随材料变形温度、应力和激活能等参数变化的本构方程,采用简化的关系式拟合了不同变形温度下的材料流变应力应变曲线,拟合效果较好。

Abstract:

The hot compression curves of Nb bulk materials were measured by Gleeble-3500 thermal simulation machine. The flow stress behavior and the deformation microstructures of the materials were analyzed at the temperature range of 350-480 ℃ and the strain rate range of 0.001-10 S_-1. It is shown that the flow stress reduces with the increasing of the deformation temperature and the strain rate. The elongated grains coarsen with the decreasing of the temperature. And dynamic recovery occurs during the hot compression. The soften mechanism also works by the dynamic recovery. Moreover, the constitutive equation of the strain rate affected by the temperature, strain and the hot deformation activation energy was deduced by the help of the modified hyperbolic sine function of Arrhenius and factor of Zener-HolIomon parameters. The simplified relation was adopted to fit the curves of the flow stress versus the strain at different temperature resulting in good effect.