Abstract
In this research, in-situ Al-SrB6 composites were prepared and employed to inoculate A356.2(Al-7Si-0.3Mg) alloy. Al-SrB6 ingot and ribbon composites were fabricated by high-frequency melting and melt-spinning, respectively. They both have α-Al and SrB6 phases. In the ribbons, the SrB6 particles have nano-sized dimensions and distribute homogeneously in the Al matrix. With the addition of 1.0% Al-SrB6 ribbons (S4 alloy), A356.2 alloy show the optimal microstructures and properties. The YS, UTS, EL and HV of S4 alloy are 30.0%, 16.0%, 38.8% and 17.7% greater than those of A356.2 alloy (S0), respectively. Furthermore, Al-SrB6 ribbons with nanoparticles demonstrate better inoculant effects than ingots at the same additive content. After adding Al-SrB6 composites, the base alloy exhibits more pronounced ductile fracture characteristics. The clean and stable SrB6/Al interface, formed by Al and SrB6, facilitates heterogeneous nucleation, grain refining and strengthening for A356.2 alloy. It has a low interface crystallographic misfit and a few orientation relationships (ORs), which will be described and calculated. The synergistic effect of free elements Sr and B ultimately increases the formation of twins, which results in fine fibrous and granular Si.
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