Heterogeneous microstructure and unpredictable porosity distribution in Al–Si high-pressure die-castings give rise to a significant variation in their mechanical properties. This study investigated the influence of porosity distribution, volume of the largest pore, eutectic phase morphology and Mn-containing intermetallics on the tensile properties of Al–Si–Mn–Mg high-pressure die-castings. The as-cast material has a “network” of fine coralloid eutectic Si as well as blocky AlSiFeMn intermetallics in interdendritic area. The solution treatment step of the T7 heat treatment spheroidized the eutectic silicon. Tensile samples were tested in both the as-cast and T7 conditions. The yield strength (YS), ultimate tensile strength (UTS) and elongation (%E) of as-cast samples were in the ranges of 129-146 MPa, 242–282 MPa and 2.6–4.7%, respectively. After T7 heat treatment the YS, UTS and %E had ranged from 124-142 MPa, 195–207 MPa and 4.6–12.1%, respectively. The T7 heat treatment had little effect on the YS but reduced the UTS considerably. The enhanced %E can be ascribed to the spheroidization of eutectic Si. The largest pore by volume in the sample also plays an important role in determining the ductility according to three-dimensional (3D) pore morphologies obtained via computed tomography (CT). The sample with largest pore by volume has the lowest %E, indicating the %E can be estimated prior to tensile test based on the size of the largest pore by volume in the sample.

Al-Si高压压铸件的异质组织和不可预测的孔隙率分布导致其机械性能发生重大变化。这项研究调查了孔隙分布，最大孔隙体积，共晶相形态和含Mn的金属间化合物对Al–Si–Mn–Mg高压压铸件的拉伸性能的影响。铸态材料在枝晶间区域具有细珊瑚共晶硅以及块状AlSiFeMn金属间化合物的“网络”。T7热处理的固溶处理步骤将共晶硅球化。在铸态和T7条件下测试拉伸样品。铸态样品的屈服强度（YS），极限抗拉强度（UTS）和伸长率（％E）分别在129-146 MPa，242-282 MPa和2.6-4.7％的范围内。经过T7热处理后，YS，UTS和％E的范围分别为124-142 MPa，195-207 MPa和4.6-12.1％。T7热处理对YS影响不大，但大大降低了UTS。增强的％E可以归因于共晶Si的球化。根据通过计算机断层扫描（CT）获得的三维（3D）孔形态，样品中体积最大的孔在确定延展性方面也起着重要作用。具有最大体积孔的样品具有最低的％E，表明可以基于样品中最大体积孔的大小在拉伸试验之前估算％E。增强的％E可以归因于共晶Si的球化。根据通过计算机断层扫描（CT）获得的三维（3D）孔形态，样品中体积最大的孔在确定延展性方面也起着重要作用。具有最大体积孔的样品具有最低的％E，表明可以基于样品中最大体积孔的尺寸在拉伸试验之前估算％E。增强的％E可以归因于共晶Si的球化。根据通过计算机断层扫描（CT）获得的三维（3D）孔形态，样品中体积最大的孔在确定延展性方面也起着重要作用。具有最大体积孔的样品具有最低的％E，表明可以基于样品中最大体积孔的大小在拉伸试验之前估算％E。