LZ61镁锂合金热变形行为及微观组织研究

通过熔炼得到了铸态LZ61镁锂合金,对其进行了热压缩变形行为研究,分析了变形温度及应变速率对其热变形行为的影响,并建立了本构方程。结果表明,合金的应变速率敏感指数m=0.218,平均热变形激活能Q=99.21kJ/mol,合金的流变曲线均属于动态再结晶型,流变应力随着温度升高(应变速率降低)而减小。温度及应变速率对合金的动态再结晶影响显著;显微组织的变化证明了动态回复和动态再结晶的发生。铸态合金组织由α-Mg相基体及弥散分布在晶界上的β相组成。经热压缩后,在相同温度下,随着应变速率降低,组织由粗细相间的晶粒转变为细小均匀的再结晶晶粒。在同一应变速率下,随着温度升高,再结晶区域逐渐增大,晶粒明显细化。

Hot Deformation Behavior and Microstructure of LZ61 Alloy

The as-cast LZ61magnesium-lithium alloy was fabricated by smelting.The hot compressive deformation behavior and effects of deformation temperature and strain rate were analyzed.Meanwhile,the constitutive equation was established.The results show that the strain rate sensitivity index of the alloy is m=0.218,and the average hot deformation activation energy is Q=99.21kJ/mol.The rheological curves of the alloys are characterized by dynamic recrystallization,and the flow stress is decreased with increasing in temperature and decreasing in strain rate.Temperature and strain rate have a significant effect on the dynamic recrystallization of the alloy.Changes in the microstructure confirm the occurrence of dynamic recovery and dynamic recrystallization.The ascast alloy consists ofβ-phase dispersedly distributed on theα-phase matrix and grain boundaries.After thermocompression,at the same temperature,as the strain rate decreases,the microstructure is changed from heterogeneous grains to fine uniform recrystallized grains.At the same strain rate,as the temperature increase,the recrystallized region is increased gradually and the grains are refined remarkably.