急冷凝固Al-Si系粉末合金の高速超塑性

抄録

Al-17Si-4.5Cu-0.5Mg-(0∼6)Fe-(0∼2)Mm (Mm: misch metal) rapidly solidified powder metallurgy (RSP) alloys were prepared by the hot extrusion method. High temperature tensile properties and deformation behavior of these alloys at 773 K were investigated. In the Al-17Si-4.5Cu-0.5Mg alloy with various Si particle sizes, typical superplastic behavior is obtained at the same strain rate of 1×10⁻² s⁻¹. The superplastic tensile elongation increased with decreasing Si particle size. With increasing Fe content, the average matrix grain size decreased and the optimum superplastic strain rate increased, but the maximum tensile elongation decreased. The grain-size sensitivity on the superplastic strain rate is about 3, as that of other superplastic Al alloys. Misch metal addition has a significant effect of retardation of coarsening of matrix grains by uniformly precipitated Al₂(Si, Cu)₂RE (RE: Lanthanoid) particles finer than compounds including Fe, and the maximum tensile elongation was obtained at a high strain rate of 1×10⁰ s⁻¹. It is generally concluded that the superplastic elongation of Al-Si RSP alloys is affected by the size of dispersing particulates.