Grain Refining Efficiency of SHS Al–Ti–B–C Master Alloy for Pure Aluminum and Its Effect on Mechanical Properties

A new Al–5Ti–0.75B–0.2C master alloy was successfully prepared by self-propagating high-temperature (SHS) reaction from an Al–Ti–B4C system with molten Al. Microstructure and phase characterization of the prepared Al–5Ti–0.75B–0.2C master alloy show that the nearly spherical TiC particles, hexagonal or rectangular TiB2 particles, and block-like TiAl3 particles distribute uniformly in the aluminum matrix. Grain refining test on commercial pure aluminum indicates that Al–5Ti–0.75B–0.2C master alloy exhibits a better grain refining performance than Al–5Ti–1B master alloy. By addition of 0.2 wt% Al–5Ti–0.75B–0.2C master alloy, the average grain size of α-Al can be effectively refined to 160 ± 5 μm from about 3000 μm, and the tensile strength and elongation are increased by about 20% and 14.1% due to the grain refinement.