Interface structure and solute segregation behavior in SiC/2124 and SiC/6061 Al composites exhibiting high-strain-rate superplasticity

Interface structure and solute-segregation behavior in the high-strain-rate superplastic SiCp/2124 and SiCP/6061 Al composites were investigated. Evid ence for interfacial reaction between reinforcement and Al matrix, which wa s evident in the superplastic Si3N4p,w/2124 Al and Si3N4p,w/6061 Al composi tes, could not be detected in the current SiC-reinforced Al composites. Ins tead, strong solute segregation was observed at SiC/Al interfaces. Extensiv e formation of whiskerlike fibers was observed at the fractured surface of tensile samples above the critical temperature where particle weakening beg an to be seen. These results suggest that partial melting occurs at the sol ute-enriched region near SiC interfaces and is responsible for the particle weakening. The absence of reaction phase in the SiC-reinforced composite m ay explain why no endothermic peak for partial melting appears in its diffe rential scanning calorimetry curve and why its optimum temperature for supe rplasticity is generally higher than that of the Si3N4-reinforced composite .