Simple rheocasting processes

Abstract

This work describes two recently invented simple rheocasting processes. One process used a cooling slope and the other low superheat casting in order to generate semisolid slurries with spheroidal microstructures that are amenable to thixoforming. In the former process, A356 aluminum alloy was poured into the lower part of a die and immediately an upper die, containing an internal cavity, was inserted in the lower die half. The A356 alloy was in a semisolid slurry form when it flowed into the lower die via a cooling slope. In the latter process, the A356 changed from fully liquid to semisolid slurry condition by cooling in the lower die half after being poured into it as low superheat casting. The primary crystals of the cast metal in the both processes became spheroidal. There was no major observable difference between conventional thixocasting microstructures and those of the two processes used in the present study. The mechanical properties obtained in the present study were: tensile strengths of 310 MPa and 18% elongation for the process using the cooling slope, and tensile strengths of 290 MPa and 12% elongation for the process using the low superheat casting.