粉末冶金高纯铱金属的热变形行为及本构方程

Thermal Deformation Behavior and Constitutive Equation of High Purity Iridium Metal in Powder Metallurgy

粉末冶金金属铱是铱制品热加工的重要原材料。利用Gleeble-3500型热模拟实验机,在变形温度1000~1300℃、应变速率0.001~0.1 s-1的变形参数下对粉末冶金态纯铱金属进行了动态热模拟压缩实验,建立了基于峰值应力的粉末冶金高纯铱金属本构方程,以及应变修正后的高精度热变形本构方程及在实验范围内的热加工图。结果表明:纯铱金属在热加工过程中经历了加工硬化、动态回复和动态再结晶三种变形。随变形温度的升高和应变速率的降低,流动应力减小。变形温度1200~1300℃、应变速率0.01~0.001 s-1时,高纯铱的流动应力表现出明显的动态再结晶特征,此时耗散值达到最大0.28~0.33,成为此变形范围内最佳热加工区域。

Powder metallurgy metal iridium is an important raw material for hot processing of its products.Under the deformation temperature of 1000-1300℃and strain rate of 0.001-0.1 s-1,the dynamic thermal simulation compression experiments of pure iridium metal in powder metallurgy state were carried out by Gleeble 3500 thermo-mechanical simulator.The constitutive equation of pure iridium based on peak stress,the high-precision thermal deformation constitutive equation after strain correction and its thermal processing map in the experimental range were established.The results show that the pure iridium metal undergoes three deformation:work hardening,dynamic recovery and dynamic recrystallization.The flow stress decreases with deformation temperature increasing and strain rate reducing.The flow stress of pure iridium exhibits obviously dynamic recrystallization characteristics at the rage of temperature 1200-1300℃and strain rate 0.01-0.001 s-1.At this time the dissipation value reaches the maximum of 0.28-0.33,which becomes the best hot working area in this deformation range.