Effect of Post Deformation on the Structure and Properties of Sintered Al-Cu-SiC Composites

Abstract

Sintered composites of Al-8wt%Cu-10vol%SiCp were deformed by repressing or equal channel angular pressing(ECAP) at room temperature, 500°C and 600°C. Their microstructures and transverse rupture properties were compared. Repressing produced more densification than ECAP but ECAP resulted in much higher strengths than repressing. In both cases, the transverse rupture strengths, after deformation at room temperature and 500°C, are much lower than those deformed at 600°C, despite of only slight differences in density. Fractured SiC particles were observed after the deformation, very frequently at room temperature, less frequently at 500°C and rarely at 600°C. Some interfacial de-bonding between the matrix and SiC particles were also observed particularly in the ECAPed specimens. The higher bend strengths and less SiC fracturing at 600°C are attributable to the presence of an Al-Cu liquid phase during deformation. ECAP at 500°C and 600°C caused recrystallization and produced very fine grain structures. Grain refinement, as well as enhanced bonding between particles due to high shear deformation associated with ECAP, is considered the major reason for the much higher strengths. The employment of copper coated SiC instead of bare SiC particles for preparing the composites was found not beneficial neither for minimizing the particle fracturing nor for improving the properties.