往复挤压Mg-4Al-2Si-0.75Sb镁合金的显微组织与力学性能

Microstructure and mechanical properties of Mg-4Al-2Si-0.75Sb magnesium alloy by reciprocating extrusion

研究了在Mg-4Al-2Si-0.75Sb合金中加入微量Sb及往复挤压对其组织与性能的影响,重点探讨了基体组织和Mg2Si相颗粒的细化机制,分析了Mg2Si颗粒对再结晶的影响规律。结果表明:加入0.75wt%Sb后的Mg-4Al-2Si-0.75Sb合金中形成Mg3Sb2相,能有效细化粗大的α(Mg)基体组织和汉字状共晶Mg2Si相颗粒,并抑制粗大的块状初生Mg2Si相颗粒的形成;Mg-4Al-2Si-0.75Sb合金在往复挤压过程中发生受位错攀移控制的动态再结晶,通过晶界迁移、亚晶合并与转动机制形成了更为细小的α(Mg)再结晶等轴晶;随着挤压道次的增加,动态再结晶速度加快,晶粒尺寸迅速减小;挤压8道次后,α(Mg)基体和汉字状Mg2Si颗粒尺寸分别由铸态时的30μm和10μm减小到1μm和0.8μm,形成了细小、均匀的α(Mg)等轴晶组织;挤压过程中,汉字状Mg2Si依弯曲机制而破碎成块状或条状,条状Mg2Si依短纤维加载机制而破碎成块状,块状Mg2Si依剪切机制发生破碎,并随挤压道次的增加而呈细小、弥散分布;合金的力学性能随往复挤压道次的增加而显著提高。

The effects of Sb addition and reciprocating extrusion（RE） deformation on microstructure and properties of Mg-4Al-2Si-0.75Sb alloy were studied.The refinement mechanisms of α（Mg） matrix and the Mg2Si particles,as well as the effect of Mg2Si particles on the recrystallization were discussed.The results show that the addition of 0.75wt%Sb causes the formation of the precipitates Mg3Sb2 phase in alloy,which can effectively refine both α（Mg） matrix and Chinese characters-shaped eutectic Mg2Si particles,and restrain the formation of the coarse massive primary Mg2Si particles.The dynamic recrystallization which was controlled by dislocation climbing takes place during the RE process for Mg-4Al-2Si-0.75Sb alloy.The equiaxed grains were formed by crystal boundary migration,subgrain merge and twist rotation by recrystallization.The grain size decrease and the rate of dynamic recrystallization increase with the increasing of the RE passes.The grain size of as-cast α（Mg） matrix and Chinese characters-shaped Mg2Si decrease from 30 μm and 10 μm to 1 μm and 0.8 μm after 8 passes of RE,respectively.The microstructure is characterized by the fine equiaxed α（Mg） grain with homogeneous distribution of fine Mg2Si particles.The Chinese characters-shaped Mg2Si particles could break into massive or strip particles by the bending mechanism,the strip Mg2Si particles could crake by the short-fiber loading mechanism,and the massive Mg2Si particles crake by the shear mechanism during RE process.The mechanical properties of the alloy are improved obviously with the increasing of the RE passes.