Si相尺寸对快凝Al－20Si－1．3Cu－1Mg合金机械性能的影响

Effect of Si Phase Particle Size on the Mechanical Properties of Rapidly Solidified Al-20Si-1.3Cu-1Mg Alloy

研究了快速凝固Ａｌ－２０Ｓｉ－１．３Ｃｕ－１Ｍｇ合金在４００℃热暴露不同时间Ｓｉ相在尺寸上的变化及其对挤压态合金室温、高温性能的影响．试验结果表明，Ｓｉ相尺寸对合金的室温性能有一定影响，经４０℃×１０２４小时暴露后，室温拉伸强度从挤压态的３３５ＭＰａ降到２２０ＭＰａ．热暴露后材料的高温（３００℃）拉伸强度开始急骤下降，但随后σｂ下降速度变缓，说明Ｓｉ相尺寸对材料高温拉伸性能的影响不是高温拉伸强度下降的主要因素．较大的Ｓｉ相颗粒是导致材料室温断裂的主要原因．

The changes of St phase size after high temperature exposure at 400 t for different length of time and its effect on the tensile properties of rapidly soliddedAl--20St-- 1. 3Cu-- 1Mg alloy have been investigated. The results show that St phaseparticle size has definite effect on the room temperature tensile properties. The tensilestrength of as --extruded alloy dectreased from 335MPa to 220MPa after exposured for1024h. at 400℃。The high temperature tensile strength(300 ℃) dramatically decreased after 4hrs exposure at 400 ℃and then the decreasing rate became slow. This indicates that the effects of Si particle size on high temperature tensile properties is weak, however, largeSi particle contribute to the room temperature fracture of alloy.