Mechanical behavior of cast particulate SiC/AI (A356) metal matrix composites

Abstract

Mechanical tests were carried out to study the deformation behavior of particulate SiC-reinforced Al (A356) matrix composites produced through direct casting using the molten metal mixing method. The matrix alloy-Al (A356) was also tested as a control material for comparison. The elastic constant and yield strength of the composite material were found higher than those of the control alloy, but the ultimate tensile strength (UTS) and the ductility were lower. The Tsai-Halpin equation was found applicable for calculating the elastic constant if an average particle aspect ratio could be determined. The strain-hardening behavior of the tested composite material appeared very different from that of the control alloy. The high strain-hardening rate in the early stage of plastic deformation of the composite was rationalized by the interaction between the hard particles and the ductile metal matrix; on the other hand, the low hardening rate recorded from intermediate strain amplitude to fracture was attributed to the early coalescence of voids and other microdamages. Particle-matrix interface debonding, particle cracking, and void for-mation in the metal matrix were considered to be responsible for the low ductility. Deformation asymmetry of the composites was noticed, not only through the Bauschinger effect, but also through the difference in virgin specimens’ yield stresses in tension and compression.