挤压温度对AZ91D合金组织性能的影响

为提高AZ91D镁合金的综合性能,对其进行热挤压变形。分别采用300、330、360、390、420℃五个挤压温度,挤压比为45,在6300kN快速成形油压机上进行正挤压,并对挤压试样进行拉伸测试和金相观察。结果表明,热挤压变形过程发生动态再结晶,晶粒细化并均匀化,有效提高了合金综合性能。并且随温度升高,抗拉强度和屈服强度都有升高趋势,但是自390℃之后,虽然再结晶彻底,但晶粒逐渐长大,所以屈服强度继续增大而抗拉强度降低。390℃下挤压,其抗拉强度可达390MPa,屈服强度达288MPa,伸长率达11%,为较好的工艺方案。

Influences of Extrusion Temperature on Microstructure and Properties of AZ91D Alloy

In order to improve integrated mechanical properties of AZ91D alloy, its hot extrusion deformation was done. The five temperature (300,330,360,390 and 420℃) and extrusion ratio of 45 were adopted. The forward extrusion was done on prompt forming oil-pressed machine of 6400 kN. The tensile test and metallographic structure observation of the samples were done after extruding. The results show that dynamic recrystallization occurs during hot extrusion deformation, and makes grains fine and microstructure homogeneous, therefore hot extrusion can improve mechanical properties of the alloy effectively. Meanwhile, with the increase of temperature, the tensile strength and yield strength improve. But when beyond 390℃, recrystallization continues to the end, while grains grow up too, so yield strength keeps going up, while tensile strength reduces. When temperature is 390℃, tensile strength reaches 390 MPa, yield strength goes up to 288 MPa and the elongation rate is 11%. It is the optimum extrusion program.