Most metal parts are manufactured by either fully-liquid (e.g., casting) or fully-solid (e.g., forging) processes. Semi-Solid Metalworking (SSM) incorporates elements of both casting and forging for the manufacture of near-net-shape discrete parts. Applications are fuel rails, suspension arms, engine brackets, steering Knuckles,rear axle components and motor cycle upper fork plates.
SSM casting was selected for each of these applications for different reasons - high integrity, pressure tightness and design simplification. In each case SSM processing provides several unique advantages over other candidates
The process capitalises on thixotropy, a physical state wherein a solid material behaves like a fluid when a shear force is applied. The SSM process requires a nondendritic feedstock that can be produced by applying mechanical or electromechanical stirring during alloy solidification at a controlled rate, or from fine-grained materials produced by powder metallurgy or spray forming methods. This feedstock, usually in billet form, is then heated to a temperature between its solidus and liquidus and formed in dies to make near-net-shape parts.