Development of a novel 6351 Al-(Al4SiC4+SiC) hybrid composite with enhanced mechanical properties

In this research work 6351 Al alloy based hybrid composites were developed in order to get improved properties of cast 6351 Al. On ex situ incorporation of SiC and Al2O3 through stir casting at 760 °C, a hybrid 6351 Al-(SiC+Al2O3) composite has been developed that exhibited massive segregation of particles and marginal improvement in strength and ductility with respect to cast 6351 Al. However, addition of fine TiC resulted in the generation of round shaped Al4SiC4 particles and when TiC and SiC were incorporated together in 6351 Al through stir casting, a novel hybrid composite consisting of in situ Al4SiC4 and ex situ SiC reinforcements in 6351 Al matrix was developed. Both the reinforcements were found to act as the nucleation sites for primary α (causing extensive grain refinement) along with the evident engulfment effects promoting uniform particle distribution. Furthermore, Al3Ti precipitates of nano-size evolved in the microstructure. Accordingly, the 6351 Al-(4 vol% TiC+4 vol% SiC) added composite exhibited a reasonable combination of strength (UTS=205 MPa) and ductility (%elongation=12).