Modeling the direct powder semi-solid molding (DPSM) of a particle metal matrix composite

A novel processing route is being developed using semi-solid forming technology to consolidate and form a metal-matrix composite from powder in a single stage. Direct powder semi-solid molding (DPSM) allows the production of near net-shape automotive components, which are currently produced via a complex, low volume powder metallurgy process, followed by machining operations. Semi-solid processing combines lower temperatures than casting with forming loads that are lower than forging, resulting in reduced tooling costs. The non-turbulent die filling reduces the amount of trapped oxides, giving a sound microstructure. Subsequent machining costs can be minimized by producing components to near net shape. However, in order to maximize these benefits it is important to avoid processing defects such as incomplete filling or folding. A model was developed of the DPSM of AMC225xe, a mechanically alloyed aluminum alloy (AA2124) containing 25-vol% of ∼3μm SiC particles. The simulations are compared to a series of "short-shot" experiments, where the forming process is stopped at various stages during filling. The results show that the treatment of the material rheology is a key factor for accurate simulation. After validation the model was applied to the process design for complex industrial components.