Effect of sintering temperature on phase transformation during consolidation of mechanically alloyed Al86Ni6Y6Co2 amorphous powders by spark plasma sintering

Mechanically alloyed Al86Ni6Y6Co2 amorphous powders (170 h) were consolidated via spark plasma sintering in the temperature range of 300-500 °C. Various phase transformations caused during mechanical alloying of the Al86Ni6Y6Co2 powders and the effect of sintering temperature on the consolidation and devitrification behavior during the sintering of the amorphous powders were investigated. XRD and TEM study confirmed a decrease in amorphous phase content with increased amount of nanocrystalline FCC-Al and nano-sized intermetallic precipitates as the sintering temperature was increased. High current density at irregular particle contact surfaces during spark plasma sintering resulted in intense Joule heating with rapid temperature rise, which caused localized devitrification along with improved consolidation. Amorphous alloy sintered at 500 °C yielded higher hardness (298 ± 9 Hv) in comparison to the lower temperature sintered alloys, attributed to better densification and uniformly distributed nanocrystalline phases in the amorphous matrix.