圧縮ねじり加工による過共晶Al-Si合金の組織微細化

抄録

Hypereutectic Al-Si alloy has excellent properties such as high temperature strength and high wear resistance owing to the presence of dispersed Si particles. However, its ductility and formability are reduced by such precipitates. To solve this problem, the microstructure refinement and homogeneous dispersion of a fine Si phase are necessary. The authors have investigated the microstructure refining method for hypereutectic Al-Si alloy by compressive torsion processing (CTP). It is an effective severe plastic deformation process which entails the simultaneous application of compressive and torsional loading to a cylindrical work piece. In this study, the effects of compressive torsion processing temperature and torsion number on the microstructure refinement of hypereutectic Al-Si alloy are dealt with. When CTP was applied on Al-Si alloy, primary Si and eutectic Si were refined more effectively at lower temperatures but they were dispersed more uniformly at higher processing temperatures. As torsion number increased, primary Si and eutectic Si were refined not only near the upper and lower dies but also inside the specimen.