The Study On Microstructure And Mechanical Property Of High Performance Hypoeutectic Casting Al-Si Alloy

Hypoeutectic Al-Si alloy has many excellent properties, such as low specific density,high specific strength, good casting property and machinability, etc. It is widely used inindustrial production and has great potential for development。In this paper, the effect of melt process （including melt purity，refinement andmodification） on the mechanical property of hypoeutectic Al-Si alloy was researched. Themicrostructure changes after adding Mg, Cu alloying elements and T6heat treatment havebeen analyzed. The phase structure and fracture morphology are studied by means ofXRD、SEM、TEM.The results show that Ti, Zr, rare earth element has an significant effect on grainrefinement, can enhance mechanical properties. But Rare Earth Elements has an effect onAl-Si casting alloys in many aspects, not only can refine primary α phase particle, but alsoon eutectic silicon phase, Rare earth elements can also form some intermetallic compoundswith a variety of elements in the alloy, can significantly enhance mechanical properties.The microstructure morphology of Al-Si alloy began to change after adding Cu andMg elements. The mechanical property was improved, because Cu could cause latticedistortion of solid solution in the base of α-Al. There are two kinds of existing form of Mgelement in Al-Si alloy, one is dissolve into α-Al matrix and the second form isintermetallic compounds. XRD analysis showed that the Cu and Mg elements mainlyformed θ-Al₂Cu, Q/W-Al_xCu₂Mg₈Si₆phase and so on in the Al-Si-Cu-Mg alloy. Thosephases partially dissolve and form supersaturated solid solution during solution treatmentand re-precipitating dispersed precipitation phaseθ-Al₂Cu、Q/W etc during agingtreatment, this can enhance the mechanical properties of the alloy.