Microstructural evolution and mechanical properties of severely deformed Al-12Si casting alloy by equal-channel angular extrusion

Abstract

Microstructural evolution and mechanical properties of Al-12Si alloy subjected to equal-channel angular extrusion (ECAE) were investigated. The high stresses imposed in ECAE led to the fragmentation of the needle-shaped eutectic silicon plates into smaller particles. The length and width of the Si particles decreased from 35.5±31.8 μm and 13.7±8.9 μm without ECAE to 2.7±1.1 μm and 1.3±0.4 μm after six ECAE passes, respectively. The average aspect ratio of 3.2±1.8 for the Si particles in the as-cast condition decreased to 1.18±0.8 after six ECAE passes with a corresponding increase in the average roundness of 0.26±0.19 to 0.61±0.19. ECAE increased the strength, ductility, and impact toughness of the alloy. The increase in the tensile and yield strengths after six passes was about 68 % and 100 %, respectively. The alloy after six ECAE passes exhibited 12 % elongation to failure, which was almost eight times higher than that of the as-cast alloy. The absorbed energy increased with an increase in the number of passes, finally reaching 11. 5 J/cm2 after six passes, which is about four times higher than that of the as-cast alloy.