Grain refinement and eutectic modification of A356 casting alloy by adding Al-B-Sr master alloys and its effect on tensile properties

The effects of the grain refinement and eutectic Si modification on tensile properties by using Al-B-Sr master alloys in A356 cast alloy were investigated. Two different master alloys, Al-4%B-1%Sr (4B1Sr) and Al-3%B-3%Sr (3B3Sr), were developed. In microstructure observation, the master alloys were consisted of AlB 2 , SrB 6 , AlSrF, KAlF 4 and Al 4 Sr compounds. It should be noted that the α-Al phase also exists in two master alloy. The result showed that the AlB 2 area fraction in the 4B1Sr alloy was higher than the 3B3Sr alloy. The 4B1Sr alloy has better efficiencies of α -Al grain refinement and eutectic Si modification than the 3B3Sr alloy, and α -Al grains are refined from 3035 to 312 μ m and the eutectic Si is modified from the acicular to fibrous morphology. The tensile properties of 4 wt% treated with 4B1Sr alloy has higher UTS and elongation compared to the treated with 3B3Sr alloy.