In this thesis,an investigation of a THX540 (AlMg5Si2Mn) alloy with respect to the entire Thixocasting process was examined. The aim was to optimize the Thixocasting process and thus improve the quality of the as-cast part. To successfully produce a Thixocast part the choice of appropriate alloy composition, the appropriate microstructure in the billet and the appropriate heating of billets into the semi-solid state, were found to be critical. In order to determine the influence of the alloy composition on fraction solid, simulations using Thermocalc were conducted. Energy profiles and heating curves from heat treatments were analysed to optimize the heating of billets. The special microstructure of billets were examined for grain size and cell size. To determine the characteristics of the as-cast part the grain size, circularity, the intermetallic phases (examined with SEM), the casting defects, and mechanical properties e.g. hardness and tensile strength, were investigated. The casting examined was manufactured for use in the automobile industry. The Thixocasting process was comprehensively described. Problem areas were identified and solutions proposed.