In this paper, the effects of the Mg content on the microstructure, mechanical properties and fracture behavior of wrought Al–8Si–(<0.01~1.32)Mg (mass fraction, %) alloy sheets in T6 temper were systematically studied by OM, SEM/EDS, EBSD, LSCM, DSC, TEM and tensile tests. The results show that the size of Si particles decreased slightly with the increase of Mg content, and the recrystallized grain size of experimental alloy sheets was refined from about 16 µm to about 11 µm. The size of β" phases did not change obviously, but its volume fraction increased gradually and then became stable. When Mg content was 1.32%, there were many associated aggregation areas of Mg₂Si particles and Si particles in alloy sheet. In addition, the strength of experimental alloy sheets showed an initial increase followed by a slight decrease as the Mg content increased, while the elongation gradually decreased. The finite element model accurately predicted the yield strength of Al–8Si–(<0.01~1.32)Mg alloy sheets in T6 temper, and the model was able to quantify the contribution of various strengthening mechanisms to the yield strength of the alloy sheets. The predicted results were in good agreement with the actual measured results. The tensile fracture mode of Al–8Si alloy sheet was ductile fracture. When Mg content was greater than 0.51%, the fracture pattern of the sheets comprised a combination of ductile and brittle fractures. With the increase of Mg content, the number of dimples in experimental alloy sheets increased slightly, the depth gradually became shallow and the size slightly decreased. Meanwhile, most secondary cracks on the surface of the Al–8Si alloy sheets after tensile fracture bypassed the Si particles and a few sheared the Si particles. With the Mg content gradually increasing to 0.78%, the number of Si particles sheared by secondary cracks gradually increased. However, When Mg content was 1.32%, the intergranular fracture phenomenon of Al–8Si–1.32Mg in T6 temper was weakened or even disappeared. There were multiple particles embedded in the same dimples in the tensile fracture. The particles in the associated aggregation areas were more easily broken.

本文采用光学显微镜、扫描电镜系统研究了Mg含量对变形Al-8Si-(<0.01~1.32)Mg(质量分数,%)合金板材在T6状态下显微组织、力学性能和断裂行为的影响。 /EDS、EBSD、LSCM、DSC、TEM 和拉伸测试。结果表明，随着Mg含量的增加，Si颗粒尺寸略有减小，实验合金薄板的再结晶晶粒尺寸从16 µm左右细化到 11  µm左右。β"相尺寸变化不明显,但其体积分数逐渐增大后趋于稳定。当Mg含量为1.32%时,Mg 2 伴生聚集区较多_。Si颗粒和合金薄板中的Si颗粒。此外，随着镁含量的增加，实验合金板的强度呈现出先升高后略有下降的趋势，而延伸率则逐渐下降。有限元模型准确预测了 T6 状态下 Al–8Si–(<0.01~1.32)Mg 合金板材的屈服强度，该模型能够量化各种强化机制对合金板材屈服强度的贡献。预测结果与实际测量结果吻合较好。Al-8Si合金薄板的拉伸断裂模式为延性断裂。当 Mg 含量大于 0.51% 时，板材的断裂模式为韧性断裂和脆性断裂的组合。随着Mg含量的增加，实验合金板的韧窝数量略有增加，深度逐渐变浅，尺寸略有减小。同时，Al-8Si 合金薄板拉伸断裂后表面的二次裂纹大部分绕过 Si 颗粒，少数剪切 Si 颗粒。随着Mg含量逐渐增加到0.78%，被二次裂纹剪切的Si颗粒数量逐渐增加。但是，当Mg含量为1.32%时，Al-8Si-1.32Mg在T6状态下的沿晶断裂现象减弱甚至消失。在拉伸断裂中，有多个颗粒嵌在同一个凹窝中。相关聚集区域中的颗粒更容易破碎。拉伸断裂后 Al-8Si 合金板材表面的大部分二次裂纹绕过 Si 颗粒，少数剪切 Si 颗粒。随着Mg含量逐渐增加到0.78%，被二次裂纹剪切的Si颗粒数量逐渐增加。但是，当Mg含量为1.32%时，Al-8Si-1.32Mg在T6状态下的沿晶断裂现象减弱甚至消失。在拉伸断裂中，有多个颗粒嵌在同一个凹窝中。相关聚集区域中的颗粒更容易破碎。拉伸断裂后 Al-8Si 合金板材表面的大部分二次裂纹绕过 Si 颗粒，少数剪切 Si 颗粒。随着Mg含量逐渐增加到0.78%，被二次裂纹剪切的Si颗粒数量逐渐增加。但是，当Mg含量为1.32%时，Al-8Si-1.32Mg在T6状态下的沿晶断裂现象减弱甚至消失。在拉伸断裂中，有多个颗粒嵌在同一个凹窝中。相关聚集区域中的颗粒更容易破碎。T6回火Al-8Si-1.32Mg的晶间断裂现象减弱甚至消失。在拉伸断裂中，有多个颗粒嵌在同一个凹窝中。相关聚集区域中的颗粒更容易破碎。T6回火Al-8Si-1.32Mg的晶间断裂现象减弱甚至消失。在拉伸断裂中，有多个颗粒嵌在同一个凹窝中。相关聚集区域中的颗粒更容易破碎。