Microstructure and Mechanical Properties of Mg-12Al- 0.7Si Magnesium Alloy Processed by Equal Channel Angular Pressing

摘要:

研究了Mg-12Al-0.7Si镁合金在等通道转角挤压过程中微观组织与力学性能随着挤压道次的变化行为。结果表明，随着挤压道次的增加，基体晶粒不断细化。6道次细化效果最佳，从铸态约90 μm细化至约8 μm，连续网状分布的β-Mg17Al12相被挤碎至约4 μm，汉字状Mg2Si相破碎且趋于均匀分布，8道次挤压后平均尺寸为2~3 μm。室温抗拉强度和伸长率在6道次和8道次挤压后达到最高，分别为293 MPa和5.1%。高温抗拉强度和伸长率在2道次和6道次挤压后最佳，分别为204 MPa和34.4%。基面(0002)晶面取向随挤压道次增加而逐渐增强，形成基面变形织构

Abstract:

Equal-channel angular pressing (ECAP) experiments were conducted on a Mg-12Al-0.7Si magnesium alloy to investigate the influence of extrusion pass on its microstructure and mechanical properties. Homogeneously refined grains and secondary Mg17Al12 particles have been observed after multiple pass ECAP processing at 573 K. Mg2Si phase with size of about 2~3 μm has been observed after 8-pass ECAP processing; its morphology changes from initial coarse Chinese script shape to fine granule polygonal shape and its distribution tends to dispersing. The ultimate strength and the elongation of the alloy at room temperature remarkably increase to 293 MPa (after 6-pass processing) and 5.1% (after 8-pass processing), respectively. During the high temperature (200 °C) test, 2-pass processed specimen exhibits high strength of 204 MPa, and the 6-pass processed specimen has better elongation of 34.4%. The high strength of ECAPed alloy is attributed to grain refinement and modification of the second phase during ECAP, especially the Mg2Si phase. It is also shown that the basal plane texture (0002) developed by repetitive ECAP pressing influences the mechanical behavior of the ECAP-processed alloy