Processing of aluminium alloys in semi-solid state: A competitive technology for automotive components

The achievement of lighter automotive components is an important driving force in the development and optimization of casting techniques. Among these, Thixocasting and Squeeze Casting of aluminium alloys are presently used in the production of security components. In the present work, several production routes and aluminium alloys are considered. A die has been designed to produce a standard security component: an automotive brake caliper. Simulation studies have been carried out to detect possible filling or solidification problems during casting and to solve them beforehand. Afterwards, automotive components have been produced with both a commercial globular structured A357 alloy through a semi-solid technology (Thixocasting) and a conventional A357 alloy by Squeeze Casting. General considerations of both casting processes are presented and some specific problems encountered are outlined. For comparison purposes, the automotive component selected has been also manufactured by means of other conventional casting technologies: sand casting, gravity die casting and low pressure die casting. Components from both sets of experiments have been heat treated and metallographic samples from problematic areas of the component selected have been thoroughly analyzed. Mechanical properties have been measured from tensile samples and the results compared for the different casting techniques evaluated.