Semi-Solid Processing of Metallic Materials

Semi-solid processing involves forming metallic alloys between the solidus and the liquidus. For the process to operate, the microstructure must consist of solid spheroids in the liquid matrix, rather than dendrites. The material then flows when it is sheared but thickens again when allowed to stand, i.e. it behaves thixotropically. This type of behaviour was first discovered by Flemings and co-workers in the 1970s and is utilized in a family of processes, some now applied commercially. Here the current status of semi-solid processing, both technologically and from a research point of view, will be reviewed.