Thixocasting and low-pressure/counter-pressure diecasting: processes for production of high-quality casting of Al-alloys

摘要

Thixocasting of semi-solid Al-alloys, as well as low-pressure and counter-pressure diecasting of selectively ceramic reinforced aluminum, i.e., with gradient microstructure, belong to the group of innovative process and materials combinations. Incompetition with various manufacturing processes, they are opening up new possibilities for the production of cast parts. This paper reports on both basic and application-related research on these processes and contains and assessment of their potential.In the field of thixocasting, an analytical process, based on a conventional penetration testing method, has been used to investigate the flow behavior in the semi-solid state. The experiments show that a basic change in the consistency of the semisolidmetallic material occurs within the relevant temperatures for thixoforming. The microstructure and properties of a thixocast rib-structured part have been investigated by processing the A357 alloy and the high-strength AMZ 62 alloy. An analysis of theflow behavior during the filling was carried out by means of step-shooting experiments.In the field of low-pressure/counter-pressure diecasting, a hollow half-sphere type casting was chosen to investigate the influence of process parameters. For the selectively reinforced casting, a good infiltration of the preforms, on the one hand, andadequate quality in the non-reinforced areas, on the other hand, were achieved. The influence of the different parameters, like die temperature and pressure difference during filling and solidification, on the properties and the porosity was shown.