Si和Mg的添加量对Al-Mg-Si合金的显微组织和Mg2Si相形貌的影响

采用光学显微镜(OM)、扫描电子显微镜(SEM)等方法研究Al-8.8Mg-9.2Si、Al-12.6Mg-7.4Si、Al-15.4Mg-9.8Si三种不同计算Mg2Si含量的合金在金属型下的铸态凝固组织演化,结果表明,合金的凝固路径为,室温下的凝固组织为一定量的初生Mg2Si相、二元共晶和三元共晶集群构成。随着Si含量和Mg含量的增加,初生Mg2Si相的数量增加,其生长形态由八面体多边形向二次枝晶壁较为发达的树枝晶状转变,共晶Mg2Si相的形态并没有明显的转变。通过对比Al-12.6Mg-7.4Si、Al-15.4Mg-9.8Si合金的凝固组织形貌,发现共晶晶胞的纵横比率累积值随着计算Mg2Si含量的增加而下降。

Effects of varying Si and Mg levels on the microstructural and eutectic Mg2Si morphology in die-cast Al-Mg-Si alloys

Solidification microstructure evolution of as-cast Al-8.8Mg-9.2Si, Al-12.6Mg-7.4Si and Al-15.4Mg-9.8Si with different calculated Mg₂Si content in the ferrous mold were studied by optical microscope(OM) and scanning electron microscope (SEM).The results show that the solidification path of the three alloys are . The solidification microstructure at room temperature is composed of a certain amount of primary Mg₂Si phase, binary eutectic and ternary eutectic clusters. With the increase of Si content and Mg content, the number of primary Mg₂Si phase increases, its growth morphology changes from octahedral polygon to dendritic with more developed secondary dendritic walls, but the morphology of the eutectic Mg₂Si phase did not change significantly. The solidification microstructure morphology of Al-12.6Mg-7.4Si and Al-15.4Mg-9.8Si alloys was compared, it was found that the cumulative value of the aspect ratio of eutectic cells decreased with the increase of Mg₂Si content.