Preparation of a novel Al-3B-5Sr master alloy and its modification and refinement performance on A356 alloy

A novel Al-3B-5Sr master alloy has been prepared through in situ synthesis method in Al melt. The as-prepared master alloy was then used to modify A356 alloy. The microstructures of the Al-3B-5Sr alloy and modified A356 alloy were investigated. The results showed that the Al-3B-5Sr alloy mainly consisted of phases of alpha-Al and granular SrB6, while the Al-3B-5Sr-7Si alloy contained irregular blocky Al4Sr phase, AlB2 and Si besides the above-mentioned phases. Satisfactory grain refining and modifying effects were obtained by the addition of Al-3B-5Sr alloy (0.5 wt.%) to the A356 alloy. Meanwhile, the morphology of eutectic silicon was changed from needle/platelike form to fibrous/globular form. The sizes of the alpha-Al dendrites decreased from similar to 1000 mu m to similar to 300 mu m. The mechanical properties of A356 alloy has been improved significantly with 0.5 wt.% Al-3B-5Sr alloy addition. (C) 2014 Elsevier B.V. All rights reserved.