Rheological properties of alloys near solidus point intended for thixoforming

Abstract

Thixoforming processes are more and more popular in automotive industry. At present, the shaping a lot of components from cast aluminium alloys in the semi-solid state is performed and possibility of application of both wrought aluminium and steel alloys is investigated. The main goal of this work is the analysis of the rheological properties of metal alloys at high temperatures, just below the solidus point, and in the semi-solid state with low liquid phase content. The data obtained from the analysis can form the basis of numerical simulation for designing and optimizing the thixoforming processes. The rheological properties should be known over a wide temperature range so that the simulations could also predict defects such as incomplete die filling. The analysis concerned both aluminium alloys (A356, 7075) and a steel alloy (M2). The paper also discusses development of globular microstructure in partially melted alloys.