HIGH TEMPERATURE DEFORMATION BEHAVIOR OF Al-SiCp METAL MATRIX COMPOSITES

Aluminum-silicon carbide (Al-SiCp) metal matrix composite (MMC) materials were fabricated using the powder metallurgy (PM) techniques of hot compaction followed by hot extrusion. Different reinforcement weight fractions were used, i.e. 0, 2.5, 5, and 10 wt% SiCp. Hot tensile deformation tests were used to characterize the ductility deformation and strength at different temperatures, i.e. T = 0.3 Tm, 0.4 Tm, 0.5 Tm, and 0.6 Tm (where Tm is the absolute melting point of the matrix material), and at different strain rates, i.e. ε• = 2 x10-3 s-1, and 0.6 Tm 100x 10-3 s-1. Brief microscopic examination was used to support the analysis of results. It was found that the stress-strain behavior is dominated by work-hardening at the lower temperature range. The work-hardening exponent (n) decreased as T increased and as reinforcement weight fraction increased but increased as ε• increased. As reinforcement weight fraction increased, considerable strengthening was achieved compared to the unreinforced matrix. The reinforcement particles dominated the plastic flow and reduced the effect of high temperature in reducing the flow stress. However, as reinforcement weight fraction increased, the tensile strength σu, as well as the yieled strength, σy were negatively affected specially at high deformation temperatures and at high strain rates. σu was found to be more negatively affected than σy. σy and σu of the unreinforced material increased as ε• increased, for all tested temperatures. As reinforcement particles were introduced to the matrix, the two parameters increased with strain rate up to ε• = 50 x 10-3 s-1, then decreased as ε• = 100 x 10-3 S-1. Maximum reduction in σy was obtained at T = 0.4 Tm at ε• = 100 x 10-3 s-1. Ductility expressed by the strain to facture, εf, decreased with the increase in ε•, for all investigated materials. Minimum εf was obtained for Al-10 wt% SiCp as T = 0.4 tm and ε• = 100 x 10-3 s-1 was applied.