Effects of Al–3Ti–3B–1Y master alloy on the microstructure, mechanical properties and electrical properties of Al–9Si–0.5Mg casting alloy

Abstract

In this paper, the correlations among the addition content of Al–3Ti–3B–1Y refiner, microstructure, mechanical performances and electrical properties were investigated. The prepared refiner was constituted of α–Al, TiAl3, TiB2, AlB2 and Ti4Al43Y6 phases. The 3.0 wt% refiner-reinforced Al–9Si–0.5Mg alloy had the highest resistivity and the optimal mechanical properties: the tensile strength of 236 MPa, yield strength of 121 MPa, elongation of 3.2% and hardness of 90 HB. They successively increased by 16.8%, 14.2%, 32.1% and 15.4%. The strengthening effect mainly originated from the refinement of α–Al phase. The grain size of α–Al phase decreased from 62.3 to 47.8 and then increased to 49.0 μm with the increase of adding amount from 0 to 3.0 and 4.0 wt%. In addition, the resistivity can be used to further determine the structural evolution and strengthening mechanism. Based on the microstructure and resistivity, it can be deduced that the enhancement of mechanical properties results from the grain refinement of α–Al phase, the eutectic refinement, the solid solution strengthening effect and the precipitation strengthening effect. Besides, the toxic effect of Y on the Al–Ti–B refiner can be avoided via regulating the adding amount of refiner.