中文摘要：

AZ81镁合金在汽车行业应用广泛,但存在组织粗大,力学性能差等缺点。等通道转角挤压渊ECAP冤法是细化晶粒,提高镁合金性能的有效途径。在300℃下对AZ81镁合金进行了1～6道次ECAP挤压,并分析了AZ81镁合金在ECAP挤压变形过程中微观组织与力学性能随挤压道次的变化规律。结果表明,随着挤压道次的增加,基体晶粒尺寸先减小后增加,4道次时细化程度最高；合金硬度先增大后减小,4道次时合金硬度最高,达到142HL；合金的抗拉强度﹑伸长率逐渐增强后减小,再增大,6道次时合金的综合拉伸性能达到最高,抗拉强度210 MPa,伸长率15.8%。

英文摘要：

AZ81 magnesium alloy is widely used in the automotive industry,but there are disadvantages of coarse microstructures and poor mechanical properties. Equal channel angular pressing （ECAP） technology is an effective way to refine grain and improve mechanical properties of the magnesium alloys. AZ81 magnesium alloy was extruded by 1-6 passes ECAP at 300℃. The microstructure and mechanical properties of AZ81 magnesium alloy changing with the extrusion pass were analyzed in ECAP the extrusion de forming process. The results show that with the extrusion pass increasing, the grain size decreases first and then increases, and the degree of refinement is the highest at 4 passes; the hardness of the alloys first increases and then decreases, and hardness is the highest （142HL） at 4 passes; the tensile strength and elongation of the alloy first gradually increase, then decrease and then increase again, and comprehensive tensile properties are the highest （tensile strength of 210 MPa and elongation of 15.8%） at 6 passes.