基于挤压铸造过程微观孔洞的形成机理, 建立了模拟铝合金挤压铸造过程微观孔洞的数学模型. 该模型考虑了传热、凝固收缩、补缩流动、压力传递、氢(H)的再分配等因素, 通过计算凝固收缩导致的补缩流动与压力降低, 以及挤压过程的压力传递, 获得挤压铸造过程糊状区的压力分布, 结合微观孔洞形成条件及H的守恒方程, 计算微观孔洞的体积分数. 对不同工艺条件下铝合金挤压铸造微观孔洞进行了模拟计算, 计算结果与实验结果基本吻合. 计算结果还表明, 适当提高模具温度和挤压压力有利于减少微观孔洞缺陷.
A mathematical model for simulating the microporosity in squeeze casting of aluminum alloy has been developed, in which the heat transfer, solidification shrinkage, feeding flow, pressure transfer, and hydrogen conservation were taken into account. The shrinkage induced flow and the pressure drop in the mushy zone were calculated by solving continuity and momentum equations. A mechanical model was solved for obtaining the pressure transferred into the central area of the casting. By coupling the pressure drop with the pressure transferred into the central area, the pressure distribution in the mushy zone was calculated. Based on the hydrogen conservation equation, the microporosity volume fraction was calculated by referring to the pressure value in the mushy zone. The squeeze casting processes of aluminum alloy under different process conditions were simulated and the simulation results were compared with experimental results. It was shown that the simulation results agree well with the experimental results, and the increases in applied pressure and mould temperature tend to reduce the microporosity in the castings.
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