Improving the Microstructures and Mechanical Properties of Hypereutectic Al-Si Alloys by Spray Forming Technique

摘要

The hypereutectic Al-Si alloys with different Cr additions have been prepared by spray forming and cast processes. With adding Cr into Al-25Si-5Fe-3Cu (wt.%, denoted as 3C) alloy, the long needle-like δ-Al_4FeSi_2 phases in the cast 3C alloy were almost substituted by skeletal α-Al(Fe,Cr)Si phase, which was refined into granular α-Al(Fe,Cr)Si phase (≤ 3-5 μm) in Cr-added deposits. By using hot extrusion almost full densification of the deposits can be made, but induces coarsening of Fe-bearing phases in as-deposited 3C and CIO (adding 1.0 wt.% Cr into 3C alloy) alloys. The size of the granular α-Al(Fe,Cr)Si phase is still less than 5 μm after hot extrusion of the as-deposited C20 alloy, while some plate-like β-Al_5(Fe,Cr)Si phases (～20 μm) disappeared. The thermal stability, mechanical properties were also evaluated.