Abstract:The gas induced semi-solid (GISS) process was developed to create semi-solid slurry with fine and uniform globular structure. The combination of local rapid heat extraction and vigorous agitation by the injection of fine inert gas bubbles through a graphite diffuser in molten metal held at a temperature above its liquidus temperature changes the morphology of primary α(Al) from coarse dendritic to rosette-like and finally to fine globular. The GISS process produced semi-solid slurry at low solid fractions and then formed the slurry by a squeeze casting process to produce casting parts. The effects of primary phase morphology on the mechanical properties of Al-Si-Mg-Fe alloy were investigated. The results show that the ultimate tensile strength and elongation are affected by the shape factor and particle size of the primary α(Al).

Key words: gas induced semi-solid (GISS); microstructure; mechanical properties; semi-solid slurry casting; rheocasting