Research and development of gas induced semi-solid process for industrial applications

Several rheocasting processes are developed or applied worldwide in the metal forming industry.One of the new rheocasting processes is the gas induced semi-solid(GISS) process.The GISS process utilizes the principle of rapid heat extraction and vigorous local extraction using the injection of fine gas bubbles through a graphite diffuser.Several forming processes such as die casting,squeeze casting,gravity casting,and rheo-extrusion of the semi-solid slurries prepared by the GISS process have also been conducted.The GISS process is capable of processing various alloys including cast aluminum alloys,die casting aluminum alloys,wrought aluminum alloys,and zinc alloys.The GISS process is currently developed to be used commercially in the industry with the focus on forming semi-solid slurries containing low fractions solid(< 0.25) into parts.The research and development activities of the GISS process were discussed and the status of the industrial developments of this process was reported.

Effects of primary phase morphology on mechanical properties of Al-Si-Mg-Fe alloy in semi-solid slurry casting process

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).

Semi-solid gravity sand casting using gas induced semi-solid process

The semi-solid metal forming using high pressures has been applied for several years.In contrast,low pressure casting,such as gravity sand casting,has not been widely studied even though it may help reduce porosity defects and offer a better casting yield.A semi-solid gravity sand casting process using the Gas Induced Semi-Solid process was investigated.The results show that the process can produce complete parts with no observable defects.The ultimate tensile strength and elongation data of semi-solid cast samples are higher than those of the liquid cast samples.In addition,the semi-solid sand casting process gives a better casting yield.It can be concluded that the semi-solid sand casting of an aluminum alloy using the GISS process is a feasible process.