THE EFFECT OF REINFORCEMENT STABILITY ON COMPOSITION REDISTRIBUTION IN CAST-ALUMINUM METAL MATRIX COMPOSITES

[摘要] A detailed microstructural characterization was performed on cast Al-7Si particulate-reinforced metal matrix composites (where the composition is in approximate weight per cent) which included extensive examination of particulate-matrix interfacial precipitation reactions. Essentially no reaction products were observed at the interface of SiC particulates. In sharp contrast, however, an extensive reaction product zone was observed at the interface and at near-interface regions of B4C reinforcement. The type of reinforcement was shown to have a profound effect on the interfacial precipitation, the elemental composition distribution and the as-cast and solution-treated-and-aged microstructures of the matrix alloy. The stability of SiC particulates in the A356 matrix alloy (Al-7Si-0.35Mg-0.2Ti) was substantially greater in comparison with highly reactive B4C particulates. Electron microprobe, scanning electron microscopy and scanning transmission electron microscopy were used to identify and analyze phases associated with the bulk matrix microstructure and the particulate-matrix interfacial reaction zones. The extensive matrix-reinforcement reactions caused selective partitioning of matrix alloying elements, thereby modifying the matrix microstructure in the composites by compositional redistribution in the matrix. B4C significantly modified the matrix microstructure of the composite, whereas the matrix containing SiC particulates remained essentially unchanged.

[发布日期] 1991-01-20