Effect of Holding Time of the Al/TiB₂ Melt at the Pouring Temperature on the Formation and Size of TiB₂ Particles Formed

In this work, A356 based metal matrix composite with a maximum of 6% TiB₂ was synthesized in-situ by mixing the halide salts viz., potassium hexa fluro titanate and potassium tetra fluro borate in calculated quantities based on the chemical reaction equation with molten A356 aluminium alloy. Nine ingots of Al/TiB₂ MMC were fabricated by maintaining the mixture of molten aluminium and the exothermic halide salts at three different melt temperatures of 750 °C, 780 °C and 810 °C and with three different holding times of 10 minutes, 20 minutes and 30 minutes after complete mixing and cast in permanent molds. In all the resulting nine number of castings, at a location where least cooling rate was observed specimens were cut for scanning electron microscopy. The size of the TiB₂ particles was found from the SEM micrographs. It was found that the TiB₂ particles were observed to grow in size both with increasing pouring temperature and increasing holding time.