Semisolid metal processing

Semisolid metal (SSM) processing is a relatively new technology for metal forming. Different from the conventional metal forming technologies which use either solid metals (solid state processing) or liquid metals (casting) as starting materials, SSM processing deals with semisolid slurries, in which non-dendritic solid particles are dispersed in a liquid matrix. Semisolid metal slurries exhibit distinctive rheological characteristics: the steady state behaviour is pseudoplastic or shear thinning while the transient state behaviour is thixotropic. All the currently available technologies for SSM processing have been developed based on those unique rheological properties, which in turn originate from their non-dendritic microstructures. Year 2001 marks the 30th anniversary of the concept of SSM processing. Today, SSM processing has established itself as a scientifically sound and commercially viable technology for production of metallic components with high integrity, improved mechanical properties, complex shape, and tight dimensional control. Perhaps more importantly, it has demonstrated its great potential for further technological development and commercial exploitation. In this paper, progress made on the scientific understanding, technological development, and industrial applications of SSM processing are reviewed. The areas for further research and development are also discussed. (C) 2002 IoM Communications Ltd and ASM International.