Direct semi-solid forming of a powder SiC-A1 PMMC: Flow analysis

Particle reinforced aluminium alloy matrix composites have proven to be one of the advanced materials capable of replacing conventional structural alloys. However, the demand for such materials has been confined to high cost applications due to their complex processing. In this paper direct semi-solid forming of the powder is explored as a low cost processing route capable of producing high quality material to near net shape. Both experimental and computational studies were performed to determine the processability of the composite. The material studied in this paper is 225xe (AA2124 reinforced with 25 vol% of 3 μm SiC particulate), which is formed into a simple test shape when semi-solid. By stopping the process at intervals before completion a series of part formed specimens (short-shots) was produced allowing the filling process to be investigated. Experimental results were compared with those from a commercial fluid flow and heat transfer model using three different viscosity functions. Accurately incorporating the viscosity as a function of solid fraction was found to be the key to successful simulations.