摘要
研究了壳型预热温度、壁厚和变质处理对A356合金显微组织和力学性能的影响,分析了工艺参数和变质剂的作用机理。结果表明,不同壳型预热温度下未变质A356合金的金相组织都为枝晶α-Al和共晶硅相,且随着壳型预热温度的升高,枝晶α-Al不断粗化、共晶硅相不断聚集和长大,未变质A356合金的抗拉强度、断后伸长率和硬度都呈现为逐渐降低的趋势;随着壁厚的增加,La变质和Sr变质A356合金的α-Al枝晶不断粗化,共晶硅相也逐渐发生聚集和长大,抗拉强度、断后伸长率和硬度都呈现为逐渐降低的趋势;采用La或者Sr变质能够细化A356合金组织,并且相对未变质A356合金具有更高的强塑性,但是La变质A356合金对壁厚的敏感性相对Sr变质A356合金更小。
The effects of shell preheating temperature,wall thickness and modification on microstructure and mechanical properties of A356 alloy were studied,and the process parameters and mechanism of modification were analyzed.The results show that the microstructure of unmodified A356 alloy with different shell preheat temperatures is dendritic α-Al and eutectic silicon phase,and the dendritic α-Al coarsening,eutectic silicon phase accumulation and growth with increasing of shell preheat temperature,the tensile strength,elongation and the hardness are decreased gradually of unmodified A356 alloy;the dendritic α-Al continuous coarsening,eutectic silicon phase gradually agglomerate and grow up,the tensile strength,elongation and hardness are gradually decreased with the increasing of thickness;La or Sr modification can refine the microstructure of A356 alloy and has higher strength and plasticity than the unmodified A356 alloy,but the sensitivity of La modified A356 alloy to wall thickness is smaller than that of Sr modified A356 alloy.
引文
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