Semi-Solid Casting of Aluminium - Scandium (Zr) Foundry Alloys

The New Rheocasting (NRC) process was applied to cast test specimens of the alloy AlSi7Mg plus minor additions of Scandium and Zirconium. In this paper the process for manufacturing of complex shaped components in semi-solid state is introduced. The semi-solid slurry is made from conventional melts by controlled cooling. There is no on - cost on the material. For comparison reasons the classical AlSi7Mg (A356) alloy was cast in a step plate die, heat treated and tested. The same treatment was given to A356 + Sc alloys. Small variations of chemical composition were chosen for the investigation of the formation of intermetallic phases and their behaviour during heat treatment.

Microstructural aspects and mechanical properties will be presented. It can be shown that additions of Scandium have a positive influence on hardness and strength of manufactured samples. The alloys show good castability and a fine grain structure which could be caused by the refining effect of Scandium in combination with Strontium. The adaptation of the well known alloy A356 with minor amounts of Scandium lead to new perspectives about using transition metals in semi-solid manufactured products.