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为了确定挤压态Mg-5Sn-2Si-2Sr合金合适的热处理方案,分别采用硬度计、X射线衍射仪、力学性能试验机、光学显微镜,研究了该合金经T4(固溶处理)、T5(200℃×12 h时效)和T6(固溶+时效)热处理后显微组织及力学性能的变化。结果表明:挤压态Mg-5Sn-2Si-2Sr合金宜采用T5热处理工艺。经T5热处理后,在晶界处析出大量Mg2Si强化相,使合金的屈服强度、抗拉强度分别达210.9 MPa、257.0 MPa,高于挤压态、T4和T6热处理工艺下的合金强度。T4热处理时,固溶强化作用远小于退火软化作用,致使合金力学性能的下降。T6热处理时,析出相及晶粒尺寸的长大使得合金力学性能的提高受到了限制。
In order to determine the suitable heat treatment scheme of Mg-5Sn-2Si-2Sr alloy, the hardness, X-ray diffraction, mechanical properties testing machine and optical microscope of the alloy were studied respectively. 200 ℃ × 12 h aging) and T6 (solution + aging) microstructure and mechanical properties after heat treatment. The results show that the T5 heat treatment process should be adopted for the as-extruded Mg-5Sn-2Si-2Sr alloy. After T5 heat treatment, a large amount of Mg2Si precipitates were precipitated at grain boundaries, yield strength and tensile strength of the alloy reached 210.9 MPa and 257.0 MPa, respectively, which were higher than that of the alloy under extrusion and T4 and T6 heat treatments. T4 heat treatment, the role of solid solution strengthening is far less than annealing softening, resulting in decreased mechanical properties of the alloy. T6 heat treatment, the precipitated phase and the growth of grain size makes the improvement of the mechanical properties of the alloy has been limited.