Development of a Novel Cast 6351 Al-Al4SiC4 In Situ Composite

In this research work 6351 Al-Al4SiC4 composite has been developed through stir casting route with incorporation of fine TiC powder in 6351 Al melt. During stir casting, round shaped Al4SiC4 particles were generated as TiC reacted with molten aluminum. These Al4SiC4 particles were found to be acting as nucleation sites for primary α (causing grain refinement) along with engulfment effects promoting particle distribution without clustering. Furthermore, as the volume fraction of Al4SiC4 particles increased, the proportion of dendritic region decreased (more equiaxed grains appeared) and the overall grain size of the matrix decreased. This resulted in an improved strength and ductility of the composite. Equations were developed with a reasonable accuracy correlating the strength with microstructural parameters. An excellent combination of strength (UTS = 215 MPa) and ductility (%Elongation = 10) was obtained for 6351 Al-7 vol.% Al4SiC4 composite as compared to base cast 6351 Al alloy (UTS = 121 MPa, %Elongation = 3).