Numerical visualization of viscosity in phase transformation forming process with controlled liquid fraction

Actual trends in the automotive industry lead to an increasing use of lightweight structures imposing the need for high strength aluminium alloys combined with complex shape. In this study, for the development of aluminium upper arm part with semi-solid die casting, series of studies have been performed. In semi-solid casting process, various defects are strongly affected by die shape than fabrication parameters because the semi-solid materials have to travel relatively long distance to fill the die cavity through a gate during filling time. To reduce the time and cost in part and die design, die filling and solidification simulation were carried out with Ostwald–de Waele rheological model. In order to propose the proper overflow position, two cavity geometry models were proposed for the variation of the overflow number and position considered in the die design by the numerical simulation. Their filling and solidification characteristics were calculated in order to propose the proper overflow position. On the basis of the computer simulation results, upper arm parts were fabricated, and defects were analysed by observing the microstructures.