基于多材质复合铸型的A356铝合金性能调控机制研究

Performance Control Mechanism of A356 Aluminum Alloy Based on Multi-Material Composite Casting

建立变壁厚回字形结构多材质复合铸型,首先,通过对A356铝合金在多材质复合铸型的充型、凝固过程模拟仿真,获得多材质复合铸型铸件充型时间和温度场结果,锆英砂与石英砂、铬铁矿砂与石英砂过渡处凝固时间呈阶梯状递减;且锆英砂与石英砂过渡处及铬铁矿砂与石英砂过渡处铸件凝固时间更短,金属液凝固速度更快。其次,采用电子背散射衍射(EBSD)分析、电子显微探针(EPMA)分析对石英砂、铬铁矿砂、锆英砂复合铸型在重力铸造下A356铝合金铸件断口进行分析并进行抗拉强度测试。结果表明:在相同壁厚时,铬铁矿砂、锆英砂型铸件的晶粒尺寸细小,Al、Mg、Si等元素分布均匀、力学性能提高,断口呈现韧性断裂的特征;同时随着壁厚减小,同种材质砂型铸件晶粒细化、元素分布均匀、力学性能提高,断口呈韧性断裂特征。

A multi-material composite casting model with variable wall thickness structure was built. Firstly, by simulating the filling and solidification process of A356 alloy in the multi-material composite casting mold, the filling time and temperature field results of the multi-material composite casting mold were obtained. The solidification time of zircon sand with silica sand, chromite sand with silica sand decreases progressively. The solidification time of casting is shorter at the transition of zircon sand with silica sand and chromite sand with silica sand, and the solidification speed of metal liquid is faster. Fracture morphology of A356 alloy casting with silica sand, chromite sand and zircon sand composite casting in gravity casting was investigated by EBSD and EPMA, and the tensile strength test was carried out. The results show that at the same wall thickness, the grain size of chromite sand and zircon sand castings is smaller, the concentration ratio of Al, Mg, Si and other elements is lower, the mechanical properties are improved, and the fracture is characterized by ductile fracture. At the same time, with the decrease of wall thickness, the grain size of sand castings of the same material is refined, the concentration ratio of elements is reduced, the mechanical properties are improved, and the fracture surface presents the characteristics of ductile fracture.