不同工艺状态下AZ31B镁合金热压缩变形行为研究

Deformation behavior research of AZ31B magnesium alloys with different process states under thermal compression

摘要:

镁合金在热加工过程中的变形机制复杂,且容易受到材料初始工艺状态和变形条件影响,因此呈现出不同的应力应变关系。采用铸态和变形态的AZ31B作为研究对象,通过Gleeble-1500获取坯料的应力应变曲线随温度和应变率的变化关系,基于Arrhenius双曲正弦型函数构建两种不同工艺状态下镁合金的本构模型,分析初始加工状态对镁合金应力应变关系及变形机制的影响。实验结果表明：当应变速率大于0.1s_^-1,变形态镁合金在低温下由于变形织构及大量孪生产生而出现45°剪切断裂；在高温和低应变速率下两种工艺状态的镁合金变形机制相同,应力应变曲线基本相似；变形态镁合金的硬化指数n及变形激活能Q相比铸态镁合金更低。

Abstract:

Deformation mechanism of magnesium alloys is complex and prone to be affected by initial process states and deformation conditions of materials during the thermal process, therefore, exhibits different stress-strain relationships. Stress-strain curves of casting and wrought magnesium alloys AZ31B were obtained by Gleeble-1500, and the constitutive models of magnesium alloys under two different initial process states were constructed based on the Arrhenius hyperbolic sine function, the effect of initial process states on stress-strain curves and deformation mechanism of magnesium alloy were analyzed. Experimental results show that wrought magnesium alloy appears shear fracture along 45° direction due to deformation texture and amounts of twins at low temperature when the strain rate is greater than 0.1s_^-1. However, The deformation mechanisms of casting and wrought magnesium alloys AZ31B keep the same at high temperatures and low strain rates, therefore, the stress-strain curves of them are basically similar. The hardening index n and activation energy Q of wrought magnesium alloys are smaller than casting magnesium alloys.