Fabrication of TiC and ZrC reinforced Al-4 wt% Cu composite droplets using impulse atomization

In this study, Al-4 wt% Cu alloy and its composites reinforced with different initial particle sizes of ZrC (8 mu m and 157 mu m) and TiC (13 mu m and 93 mu m) were fabricated by impulse atomization, and the microstructure of composite and unreinforced alloy droplets were examined by scanning electron microscopy, x-ray diffraction and cell size analyses. Scanning electron microscopic observations of composite droplets indicated that fine ZrC particles (8 mu m) were mostly clustered while the other composites of the present investigation were distributed rather uniformly within the fine microstructure of droplets. The relationship between the cell size and the amount of carbide particles reveals that the presence of carbide particles in the alloy powders yields a finer structure. This could be due to the role of the carbide particles as heterogeneous sites for nucleation and to some extent due to particle restricted growth of matrix cells during solidification.