Optimisation of microstructure and mechanical properties of new low silicon cast aluminum alloy by Sr modification and B refinement

Abstract

ABSTRACT In order to investigate the optimum refinement and modification scheme of the new low-silicon cast aluminum alloy, experiments were carried out on macroscopic grain size statistics, eutectic silicon phase morphology observation and tensile properties test for aluminum alloys with different contents of Al-3B refiner and Al-10Sr modifier. The results showed that when the amount of B added in the low-silicon cast aluminum alloy was 200 ppm, the AlB2 particle which can act as the ideal substrate for grain nucleation in the alloy can be saturated, and the alloy was distributed with fine uniform equiaxed grains while the grain size was minimised. Moreover, when the amount of Sr addition was 250 ppm, the eutectic silicon can exhibit a branched and dense coral branch because the Sr in free form was sufficiently adsorbed on the eutectic silicon. The effect of SrB6 formed by the interaction between Sr and B was the smallest. The alloy exhibited a uniform distribution of fine round grains after heat treatment, and obtained the optimum comprehensive mechanical properties. And the tensile strength reached 370.3 MPa, the yield strength was 307.3 MPa, and the elongation increased to 8.3%.