Grain refining performance for Al and Al–Si alloy casts by addition of equal-channel angular pressed Al–5 mass% Ti alloy

This paper investigated the microstructural evolution and the grain refining performance of an Al–5 mass% Ti alloy that was fabricated by the equal-channel angular pressing (ECAP) method. The microstructures were observed by a scanning electron microscopy (SEM). Platelet-shaped Al3Ti particles cracked severely with repetitive ECAP passes, and the mean size of the Al3Ti particles decreased from 70 to 3.2 μm after 15 ECAP passes. Energy dispersive X-ray spectroscopy (EDXS) and X-ray diffraction (XRD) analysis showed an Al–Ti supersaturated solid solution was formed during the ECAP process. Moreover, when the ECAPed Al–Ti alloy with the Al–Ti supersaturated solid solution was added to pure Al and Al–Si eutectic alloy melts, a better grain refining effect was obtained compared to that of the same alloy without the ECAP. It is considered that the fine Al3Ti particles and the Al3Ti precipitates from the supersaturated solid solution probably contribute to the grain refinement. The pure Al and Al–12.6 mass% Si alloy that was refined by the ECAPed Al–5 mass% Ti refiner had a high Vickers microhardness and good wear resistance. It is suggested that the ECAPed Al–5 mass% Ti alloy could become an effective refiner in commercial Al cast production.