高挤压比下挤压工艺对AZ31B镁合金组织与力学性能的影响

研究了高挤压比条件下挤压温度、速度对AZ31B镁合金微观组织、力学性能的影响。采用光学显微镜观察了显微组织,拉伸试验测试了力学性能,并配合扫描电镜观察了拉伸试样的断口形貌。结果表明,高挤压比条件下,动态再结晶较为充分,少量晶粒长大,混晶组织消失。低温、高速挤压有助于晶粒细化,并使晶粒尺寸分布均匀,因而可获得高的抗拉强度、屈服强度以及良好的塑性。350℃,2 m/min条件下挤压,试样抗拉强度与延伸率最高,为336.5 MPa与23%。低温、高速下的挤压试样的拉伸断口韧窝较深且细密,呈现明显的韧性断裂特征,而高温、低速的断口为混合断裂。

Impact of extrusion process on microstructure and mechanical properties of high extrusion ratio AZ31B magnesium alloy

We addressed the impact of extrusion temperature and velocity on microstructure and mechanical properties of high extrusion ratio AZ31B magnesium alloy.We employed optical microscopy (OM) to observe its microstructure, indoor temperature tensile test to determine its mechanical properties, and scanning electron microscopy (SEM) to observe its fracture morphology. Results show that dynamic recrystallization is complete, a few grains grow and mixed grain structure disappears for high extrusion ratio. Low temperature and high speed extrusion are benefit for fine grain and even grain distribution, so we can get high tensile and yield strength and better ductility.Its optimal tensile strength and elongation rate are 336.5 MPa and 22.5% for 350 ℃ and 2 m/min extrusion. For low temperature and high speed extrusion, its tensile fracture has finer and deep dimples, obvious ductile fracture characteristic. However, mixed fracture exists for high temperature and low speed extrusion.