基于多材质复合铸型的A356铝合金性能调控机制研究

Study on performance control mechanism of A356 aluminum alloy based on multi-material composite casting

摘要:

本文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度处凝固时间成阶梯状递减；且锆英砂与石英砂过度处与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。其次通过对石英砂、铬铁矿砂、锆英砂复合铸型在重力铸造下A356铝合金铸件进行电子背散射衍射分析（EBSD）、电子显微探针分析（EPMA）、抗拉强度及扫描断口分析。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等元素集中度低、力学性能增大，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尺寸细小、元素集中度低、力学性能增大，断口呈现韧性断裂的特征。

Abstract:

In this paper, a multi-material composite casting model with variable wall thickness structure is builded. 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 decreased progressively. The solidification time of casting is shorter at the Connection position of zircon sand with silica sand and chromite sand with silica sand, and the solidification speed of metal liquid is faster. Secondly, analysis the Electron Backscatter Diffraction Analysis (EBSD), electron microprobe analysis (EPMA), tensile strength and scanning fracture of A356 alloy casting with silica sand, chromite sand and zircon sand composite casting in gravity casting. The results show that at the same wall thickness, the grain size of chromite sand and zircon sand castings is better, the concentration ratio of Al, Mg, Si and other elements is lower, the mechanical properties are increased, 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 fine, the concentration ratio of elements is reduce, the mechanical properties are increase, and the fracture surface presents the characteristics of ductile fracture.