高速挤压Mg-8Al-0.4Zn-0.9Ca-0.2Gd-0.2Mn合金微观组织与力学性能研究

Microstructure and Mechanical Properties of High-speed Extruded Mg-8Al-0.4Zn-0.9Ca-0.2Gd-0.2Mn Alloy

摘要:

为解决商用AZ80镁合金难以高速挤压加工的瓶颈问题，本研究采用微量Ca、Gd对其进行复合合金化，在Mg-8Al-0.4Zn-0.9Ca-0.2Gd-0.2Mn（AZXVM80100, wt.%）微观组织中原位生成大量高熔点Al2Ca相、Al2Gd与Al8Mn5相。这些高熔点第二相在高速（32.4 m/min）挤压过程中稳定存在，避免了热裂纹的产生，同时显著细化动态再结晶晶粒。高速挤压AZXVM80100合金发生了完全再结晶，表现出典型的基面纤维织构，其平均晶粒尺寸为8.6±1.7 μm。归因于显著的细晶强化作用与以位错滑移为主导的塑性变形机制，挤压态AZXVM80100合金表现出优异的强度与塑性匹配，其屈服强度与延伸率分别达到257.4±4.1 MPa与14.9±0.8%。兼具优异挤压加工性能与强韧性能的AZXVM80100合金在制备低成本高强韧挤压镁合金产品方面展现出巨大潜力。

Abstract:

Improving the extrusion speed of Mg alloys is crucial for expanding their applications. Here we show a novel heavily alloyed Mg-8Al-0.4Zn-0.9Ca-0.2Gd-0.2Mn (AZXVM80100, wt.%) alloy having outstanding extrudability and good mechanical performance. It can be extruded at a die exit speed of 32.4 m/min without any hot cracks. The excellent extrudability is mainly attributed to the dominant presence of Al2Ca, Al2Gd and Al8Mn5 phases with high thermal stability, which did not melt despite the substantial amount of deformation heat generated during the high-speed (32.4 m/min) extrusion, avoidiing hot cracking. Meanwhile, these thermally stable Al2Ca, Al2Gd, and Al8Mn5 phases exerted a remarkable refining effect on the recrystallized grains. Besides, the as-extruded AZXVM80100 alloy displays a fully dynamic recrystallized microstructure. It has a typical basal texture and fine grains with an average grain size of 8.6±1.7 μm. Owing to the significant grain boundary strengthening, the as-extruded AZXVM80100 alloy demonstrates a high tensile yield strength of 257.4±4.1 MPa. Furthermore, the as-extruded AZXVM80100 alloy also exhibits a high elongation of 14.9±0.8%, which is dominantly coordinated by dislocation slip. The newly developed high speed extrudable AZXVM80100 alloy, containing large amounts of cheap elements (Al, Zn, Ca, Mn) and trace amounts of rare earth (Gd), has great potential in manufacturing extrusion profiles because of its good strength-ductility synergy.