Microstructural characteristics of thixoforged A356 alloy in mushy state

Tensile properties of a thixoforged A356 alloy were measured and compared with those of rheocast and gravity cast alloys with the same composition. In the thixoforging process, A356 rheocast alloy produced by stirring method was reheated to 600 °C or 610 °C, held for 10 min, and then 50% deformation was applied. Microstructure, tensile properties and fracture surfaces of produced specimens were then investigated. Results obtained show that tensile strength, yield strength and elongation-to-failure of thixoforged samples formed at lower temperature are higher than those of samples formed at higher temperature. By increasing temperature, in the case of thixoforged samples, tensile fracture path is changed from trans-primary alpha phase to inter-primary alpha phase. Differences observed in the tensile fracture path and improvement in the mechanical properties due to thixoforging process is attributed to microstructural changes as well as morphological aspects of silicon phase.