Effect of pouring temperature on cast Al/SiCp and Al/TiB2 metal matrix composites

Abstract

The effect of pouring temperatures of an ex situ (Al/SiCp) and in situ (Al/TiB2) metal matrix composites (MMCs) synthesized using stir casting method were studied. The Al/SiCp composite were fabricated by mixing of 6wt.% of SiCp into cast A356 aluminium alloy melt and poured at diverse pouring temperatures (730°C, 750°C and 770°C). The Al/TiB2 MMCs were obtained by melting A356 aluminium alloy and mixing of KBF4 and K2TiF6 precursor salts whose stoichiometric ratio composition corresponds to 6wt.% of TiB2 reinforcement and other parameters were constant (stirring speed 300 RPM and holding time 30 minutes). The composite melt was poured into the permanent mould with varied pouring temperatures (800°C, 820°C and 840°C). Coarser and homogenous SiC particles were presented in the Al/SiCp MMCs, whereas, finer and uniformly distributed TiB2 particles were appeared at the MMCs of Al/TiB2. The mechanical properties viz. tensile strength, fracture toughness and hardness of Al/SiCp and Al/TiB2 MMCs were experimentally determined as per the ASTM standards and compared. Higher tensile and fracture strength were occurred at the MMCs of Al/TiB2 as compared to Al/SiCp MMCs and base alloy of aluminium as well. Maximum hardness was attained at the pouring temperatures of 820°C and 750°C in the MMCs of Al/ TiB2 and Al/SiCp, respectively.