Forming of thin-walled cylindrical cup by impact backward extrusion of Al-Si alloys processed by semi-solid cast and ECAP

Abstract

Although impact backward extrusion has advantages in manufacturing of thin-walled cup at high productivity, applications are limited to materials with low strength. In order to manufacture thin-walled cup with high strength, the authors prepared JIS AC4CH cast alloys (Al-7.14%Si-0.41%Mg) having various eutectic microstructures by combination of two refinement methods: semi-solid casting and ECAP process. Thin-walled aluminum cylindrical cups were successfully formed by impact backward extrusion from the modified cast alloy. Improvement of workability for the extrusion was achieved by grain refinement. However, an unavoidable eccentricity of cup occurred without depending on workpiece materials. It is found that workability of the workpiece can be evaluated by maximum eccentricity without causing cracks. It is concluded that the ECAPed semi-solid cast alloy has workability next to annealed AA3003 alloys; a product of the ECAPed semi-solid cast alloy has high strength and ductility compared with that of annealed AA3003.