Effect of Thixoforming on the Microstructure and Tensile Properties of A356 Alloy and A356-5TiB2 In-situ Composite

Abstract

In the present work, A356 alloy and in situ A356-5TiB2 composite feedstock was produced by employing Cooling slope casting technique. The technique resulted in near spherical morphology of primary ?-Al phase in the feedstock of both the alloy and composite. A fine distribution of eutectic Si phase within the matrix was observed in the composite feedstock. The rheocast billets of both the alloy and composite were then thixoformed successfully at 50�% solid fraction temperatures of 580 and 585��C respectively. Further, tensile properties of thixoformed alloy and composite were measured and compared with those of gravity-cast samples. It was observed that the % increase in yield strength and tensile strength of thixoformed alloy increased by 43 and 36�% respectively with respect to the gravity-cast alloy. The thixoformed composite attained the highest ultimate tensile strength of 211�MPa which is about 40�% higher as compared to gravity-cast alloy. Interestingly, the ductility of the composites is comparable to that of alloy after thixoforming. � 2015, The Indian Institute of Metals - IIM.