Production of Al-based amorphous alloy powders by close-coupled gas atomization

Theoretical and experimental studies on the production of M-based amorphous alloy powders by close-coupled gas atomization were carried out. The particle size, surface morphology and microstructure of the atomized powders were analyzed by XRD, SEM, TEM and DTA. The critical cooling rate for glass formation and corresponding powder diameter of the M-based alloy were determined in terms of the breakup mode and cooling behavior of melt during atomization. It is indicated that there are amorphous particles in the atomized M-based powders, which are basically below 26μm in diameter. The critical cooling rate for glass formation of the M-based alloy is about 10⁶ K·^s-1 Melt atomization is such a complicated process that powders form under the coupling interaction of breakup and solidification, where rapid solidification (>10⁴ K·s^-1) restrains the breakup of melt; meanwhile, the breakup mode of melt has great influences on solidification. The present close-coupled gas atomization can only produce the mixture powders of crystal and amorphous particles.