Effect of castings modulus on the microstructure of Al/ SiCp metal matrix composites; fabricated via Narrow Melt Stream (NMS) method

In this study, for the first time Narrow Melt Stream (NMS) as a relatively new semi solid technique was utilized for producing globular structures in Al/SiCP metal matrix composites. Al-10 vol. %SiC composite reinforced with 76 μm sized SiC particles produced by SL version of compocasting was used as the starting material. These ingots were re-melted and poured at 660ºC through a 10 mm sized nozzle into three cylindrical shaped cast iron moulds with an identical volume of 200 cm3 and various modulus of 1, 1.2 and 1.3 cm, located at 1500 mm under the crucible. The as-cast composites exhibited non-dendritic microstructure which could be converted into a globular structure after partial re-melting. It was concluded that by decreasing the casting modulus, more spherical globules with smaller average sizes were generated. Also, the decreased casting modulus resulted in a more uniform distribution of SiC particles in the matrix alloy at the expense of higher porosity levels.

Keywords:

Narrow melt Stream (NMS) method , Al-10vol. %SiCp , castings modulus , globular structure