Microstructural refinement and property enhancement of cast light alloys via friction stir processing

Friction stir processing (FSP) is a novel metal-working technique that provides microstructural modification and control in the near-surface layer of metal components. FSP of cast Al and Mg alloys resulted in the break-up of coarse dendrites and secondary phases, refinement of matrix grains, dissolution of precipitates and elimination of porosity, thereby improving the mechanical properties of the castings significantly. Cast Ti alloys do not contain harmful secondary phases and the dendritic structure is masked by the beta to alpha allotropic transformation, but the coarse lamellar structure is undesirable. In this article, microstructure and particle refinement, accelerated dissolution of precipitates and alloy systems suitable for FSP were addressed. (c) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.