(1. 重庆大学 材料科学与工程学院, 重庆 400045；
2. 重庆大学 国家镁合金材料工程技术中心, 重庆 400045)
摘 要: 在不同温度下，采用双向双通道变通径挤压(DDE)对AZ31镁合金进行挤压，研究该工艺对其组织、力学性能、拉压不对称性和断裂行为的影响。结果表明：与均匀态AZ31镁合金相比，挤压后所得试样的晶粒显著细化，力学性能和拉压不对称性得到改善；与采用等通道角挤压工艺多道次挤压试样的力学性能相比，该工艺具有一定的优势。此外，随着挤压温度的升高，晶粒尺寸逐渐增大，显微硬度、抗拉强度和压缩率逐渐降低。从250 ℃到450 ℃，晶粒尺寸从6 μm增大到26 μm，硬度值(HV)从67降低到56，抗压强度从400 MPa降低到343MPa，压缩率从14.8%降低到9.7%。均匀态AZ31和挤压态AZ31的压缩断口均为穿晶断裂，前者断裂机理为脆性解理断裂，后者为韧脆结合型准解理断裂。
关键字: AZ31镁合金；双向双通道变通径挤压；显微组织；力学性能；断裂行为
（1. College of Materials Science and Engineering, Chongqing University, Chongqing 400045, China;
2. National Engineering Research Center for Magnesium Alloys, Chongqing University, Chongqing 400045, China）
Abstract:The AZ31 magnesium alloy was extruded by dual-directional extrusion (DDE) at different temperatures. Then, the microstructures, mechanical properties, tension and compression asymmetry and the rupture behaviors were studied. The results indicate that, compared with homogenized samples, the grain sizes of the extruded ones are all refined, thereby improving the mechanical properties and tension and compression asymmetry. The improved mechanical properties are comparable or even superior to those of the alloys subjected to the equal-channel angular extrusion several passes. Further more, with the increase of extrusion temperature from 250 to 450 ℃, the grain size increases from 6 to 26 μm, and the microhardness, ultimate compressive strength(UCS) and compressive ratio decrease from 67 to 56(HV), 400 to 343 MPa, 14.8% to 9.7%, respectively. The microstructures of fracture show that both homogenized and as-extruded AZ31 alloys cut through the grains, while the fracture mechanism of homogenized AZ31 and as-extruded AZ31 are brittle cleavage fracture and ductile-brittle quasi-cleavage fracture, respectively.
Key words: AZ31 magnesium alloy; dual-directional extrusion; microstructure; mechanical property; rupture behavior
