热变形提高Mg-3Al-1Zn-0.1Mn-0.2Ca合金的热加工性和耐蚀性

Improvement of Hot Workability and Corrosion Resistance of Mg-3Al-1Zn-0.1Mn-0.2Ca Alloy Through Hot Deformation

研究了功率耗散系数对AZ31合金热加工性和腐蚀行为的影响。结果表明:微量的Ca元素可以促进动态再结晶(DRX)而细化晶粒和形成掺杂微量Ca(OH)2更具保护性的腐蚀产物层从而提高合金热加工性和耐蚀性。失稳区由于不均匀的组织和明显的楔形裂纹耐蚀性差于DRX区域。而且流动局部带造成的楔形裂纹为侵蚀性Cl-的扩散提供了通道并加速了镁基体的进一步腐蚀。Mg-Al-Zn-Mn-Ca合金在400℃/0.001 s^(-1)热压缩得到大功率耗散系数和均匀细小组织的DRX区域同时具有优异的热加工性和耐蚀性。

The effect of efficiency of power dissipation on hot workability and corrosion behavior of AZ31 alloy was investigated.The results indicate that minor Ca-addition can significantly improve the hot workability and corrosion resistance due to grain refinement by facilitating recrystallization and formation of a more protective corrosion product layer doped with a trace amount of Ca(OH)2. The instability zone exhibits worse corrosion resistance than dynamic recrystallization(DRX) domain due to heterogeneous microstructure and obvious wedge cracks. Moreover, wedge cracks caused by flow localization band can serve as channels for the diffusion of aggressive Cl-and accelerate further corrosion of Mg matrix. The DRX domain with homogeneous fine grain microstructure and high efficiency of power dissipation obtained by hot deformation at 400 ℃/0.001 s^(-1) of Mg-Al-Zn-Mn-Ca alloy simultaneously performs superior corrosion resistance and good hot workability.