A357合金夹杂物的形态分析

Analysis on Inclusions Morphology in A357 Alloy Melting

采用金相、电镜、能谱以及原子力显微分析等方法研究了A357合金熔炼过程中坩锅熔体表面的浮渣。观察了熔体表面合金浮渣微观形貌、组织及其中的夹杂物形态,并作了成分分析。结果表明,熔体表面浮渣中的夹杂物主要呈条块状和长线状,夹杂物中含较多的Al2O3、MgO或MgAl2O4、ZnO、SiO2,还有较少的铁相;含钙相主要是Ca-Si-O复杂相夹杂物。熔体表面氧化膜有较多的显微裂纹和γ-Al2O3转变成α-Al2O3颗粒后脱落而形成的凹坑。浮渣的AFM照片中条带状和絮状的特征与基体性能相差较大,为疏松的氧化夹杂。

The optical microscope （OM）, scanning electric microscope （SEM）, energy dispersive spectrometer （EDS） and Atomic Force microscope （AFM） were used to characterize the floating scum of melt surface. The morphology, microstructure, and inclusions composition of these floating scum were investigated. The results show that the floating scum of melt surface includes Al2O3, MgO or MgAl2O4, ZnO, SiO2, and small amount of Fe phase, also includes the complicated Ca phase of Ca-Si-O. The oxide film of melt surface contains many micro-cracks and spherical pits that result from the transformation of γ-Al2O3 to α-Al2O3 and γ-Al2O3 peeling off. The features like strip and floe are porous oxide inclusions with different properties contrasted to matrix metal in AFM analysis images.