Process window for manufacturing of semi-solid aluminium alloys

Abstract

The demands of the automotive industry for lightweight technologies stimulate research on new materials and the development of corresponding innovative production methods. The thixocasting process is based on standard high pressure die casting with the exception that mould filling takes place in the semi-solid state. In comparison to other processes, thixocast parts generally have better mechanical properties. For an industrial application and for the safe handling of the partially solidified alloys in series manufacturing, an exact knowledge of the material behaviour is necessary. This paper attempts to give an overview of the relevant parameters influencing the successful processing of semisolid metals with thixotropic properties. With this aim, several parameters considered to be of major importance for the process were selected and analysed and correlated with the desired end properties. The influence of temperature to obtain an optimally heated semi-solid billet with thixotropic properties was the first parameter to be evaluated. Subsequently, the effect of wall thickness (25–0.5 mm) and metal velocity during mould filling on the mechanical properties, grain texture development and segregation phenomena was studied and analysed. As a result of the investigations, a preliminary process window for the successful processing of semi-solid aluminium alloys was defined.