Effect of Grain Modifier on Mechanical and Tribological Properties of Al-Si Alloy and Composite

This study investigates the effect of Strontium (Sr) grain modifier addition on Al-9Si alloy and B4C reinforced composite fabricated by two step gravity casting technique. The optimum level of Sr was identified as 0.08 wt.% for complete modification. The modified cast components were thermally treated by T6 temper to enhance the tribo-mechanical properties. Metallographic observation revealed the transformation of acicular Si grains to fine fibrous in as-cast condition, which later transformed to spheroidised eutectic Si after heat treatment. The combined effect of grain modification by Sr and the influence of spheroidised eutectic Si enhanced the mechanical properties. Heat treated modified composite exhibited superior tribological properties when compared to other components under varying applied normal loads and sliding distances. Worn mechanism of heat treated modified composite was observed to be minor delamination wear regime at high load (55 N) and sliding distance (1500 m).