Microstructure development in finely atomized droplets of copper-iron alloys

The solidification behavior of Cu(100-X)FeX (X = 15, 20, 30, and 40) alloys was investigated by gas atomization technology. The effects of the size and composition of the atomized droplet on the microstructure development during cooling through the metastable miscibility gap have been discussed. A smaller atomized droplet achieves a finer dispersed microstructure. Alloys of composition close to the critical composition of the alloy system are relatively easy to undercool into the miscibility gap. The forces acting on the Fe-rich sphere during the liquid-liquid phase transformation were analyzed. The formation of an Fe-poor layer on the powder surface is the result of the common action of the Fe-rich sphere's Marangoni migration and the repulsive interaction between the cellular solid/liquid interface and the solidified Fe-rich sphere. The Fe-rich spheres in the center part of the powder are entrapped between the equiaxed grains of Cu-rich phase and finally distributed at the grain boundaries and triple junctions.