热挤压AZ91D镁合金线材的组织与性能研究

Microstructure and properties of hot extruded AZ91D magnesium alloy wire

对铸态AZ91D合金进行400~460℃不同温度下的正挤压,制备出直径为3~4 mm的线材。利用光学显微镜分析线材的组织,测试其拉伸力学性能和热膨胀系数。结果表明,在不同挤压温度下均可制备出AZ91D镁合金线材,挤压温度越低,线材晶粒越细小。线材具有优异的力学性能,经400℃热挤压成形的线材抗拉强度和伸长率高达285.6 MPa和5.3%,明显高于同牌号铸态合金的性能。线材的平均线膨胀系数为（21.3~27.4）×10-6K-1。较低挤压温度下制备的线材具有较高的力学性能与较小的线膨胀系数。

As-cast AZ91D alloy was hot extruded to fabricate wires of 3-4 millimeter in diameter.The microstructure of the wires was observed by optical microscope,and tensile properties and coefficient of thermal expansion were also measured.The results show that the AZ91D wires of 4 mm diameter can be successfully produced at the temperature range of 400 ℃ and 460 ℃.The fine equiaxed grained wires can be obtained at lower extrusion temperature.The wires possess excellent mechanical properties,the ultimate tensile strength and elongation of the wires extruded at 400 ℃ are as high as 285.6 MPa and 5.3%,respectively,and are clearly higher than that of As-cast same alloys.The average coefficient of thermal expansion of the wires are in the range of（21.3-27.4）×10-6 K-1.Hot extrusion at lower temperature is helpful for fabricating wires with high mechanical properties and small coefficient of thermal expansion.