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研究了低挤压比(挤压比8)下挤压温度和挤压速度对AZ31B镁合金微观组织和力学性能的影响。采用光学显微镜观察了显微组织,采用材料拉伸试验测试了力学性能,并用扫描电镜观察了拉伸试样的断口形貌。结果表明:低挤压比时棒材的组织为典型的混晶组织——由发生再结晶的细小晶粒包裹未发生再结晶的粗大晶粒;300~400℃时,随挤压温度的提高,材料的伸长率升高,抗拉强度下降;在300℃挤压时,随挤压速度的提高,材料的伸长率升高,抗拉强度下降,挤压棒的拉伸断口由混合断裂转变为明显韧性断裂;250℃时综合力学性能最好,抗拉强度340 MPa,屈服强度280 MPa,伸长率23%。
The effects of extrusion temperature and extrusion speed on the microstructure and mechanical properties of AZ31B magnesium alloy were investigated at low extrusion ratio (extrusion ratio 8). The microstructure was observed by optical microscope. The mechanical properties were tested by the tensile test of the material. The fracture appearance of the tensile specimen was observed by scanning electron microscope. The results show that the microstructure of the bar is a typical mixed crystal structure at low extrusion ratio. The coarse grains without recrystallization are surrounded by the recrystallized grains. When the extrusion temperature is increased from 300 to 400 ℃, , The elongation of the material increased, the tensile strength decreased; extrusion at 300 ℃, with the extrusion speed increases, the elongation of the material increases, the tensile strength decreases, the tensile fracture of the extruded rod by mixing The fracture changed to obvious ductile fracture. The best mechanical properties were obtained at 250 ℃, the tensile strength was 340 MPa, the yield strength was 280 MPa and the elongation was 23%.