含Ca,Si镁合金的铸态组织及其形成机制

AS-CAST MICROSTRUCTURE AND ITS FORMATION MECHANISM IN Mg-BASED ALLOYS CONTAINING Ca AND Si

利用金相、电子显微镜、X射线衍射仪和X射线能谱仪研究了含Ca,Si镁合金的铸态组织特征.结果表明:含Si较低的合金由镁基体及CaMgSi相组成,而含Si较高的合金由镁基体及CaMgSi和Mg2Si两种相组成. CaMgSi相呈三种不同的形态:离散块状、微细点状和针状,而本身是针状的Mg2Si则以"汉字形"团块的形态存在.根据Mg-Mg2Si-CaMgSi赝三元相图,详细讨论了铸态组织的形成机制.

The as-cast microstructure of Mg-based alloys containing Ca and Si was investigated using optical microscopy, XRD, SEM/EDS and TEM. It was found, that the alloy containing low Si consisted of Mg-rich matrix and CaMgSi phase, while the alloy containing higher Si consisted Of Mg2Si besides the Mg-rich matrix and CaMgSi. The phase CaMgSi existed in three different morphologies, namely discrete large angular, dispersive dot-like, and needle-like, while the Mg2Si, also needle-like, existed in the 'Chinese-script' colonies. The formation mechanism Of the as-cast microstructure was discussed in details based on a proposed pseudo-ternary Mg-Mg2Si-CaMgSi phase diagram.