Processing of glass former alloys by spray forming

Spray forming (SF) can be classified as a two-stage manufacturing process in which solidification begins during particle flight, a relatively rapid solidification step that ends as the deposit builds up, with the remaining liquid droplets solidifying at considerably slower rates. Due to the high cooling rate of the atomization step and the special conditions of deposit buildup, with incoming materials dynamically refining the solidifying material, as-sprayed deposits typically display a fine-scale microstructure which may also exhibit some extended solid solubility and metastable phases. Our group has studied several alloys in order to investigate the potential formation of novel microstructures by this process. This paper describes some of the results obtained by spray forming of aluminum- and iron-based alloys, whose compositions derive from rapid solidification studies aimed at obtaining amorphous structures. Al85Y8Ni5Co2, Fe83Zr3.5Nb3.5B9Cu1, [(Fe0.6Co0.4)0.75B0.2Si0.05]96Nb4, and Fe63Nb10Al4Si3B20 glass-forming alloys were processed. Formation of amorphous phase was observed throughout the deposit of the Al-based alloy processed at a high G/M ratio, which was not observed in the Fe-based alloys. In addition, the [(Fe0.6Co0.4)0.75B0.2Si0.05]96Nb4 alloy, which displayed the highest glass-forming ability among the Fe-based alloys, showed a high volume percent of amorphous phase formation up to 4mm thickness of the deposit, a similar value obtained for this alloy when processed by copper mold casting.