Warm consolidation of spray-quenched amorphous NiFe-based alloy powders

Abstract

Spray-quenched amorphous powders of the alloy Ni 49Fe 29P 14B 6Al 2 were consolidated by uniaxial warm die pressing into disc samples at different temperatures T below the crystallization temperature T x under a compacting pressure σ of 0.98 GPa. The homogeneous-to-inhomogeneous transition temperature T x of deformation of the powders was determined from analysis for the ln ε vs. 1/T plot (where ε is the strain rate of the powders during compaction). Densification of compacts of the present alloy has been found to proceed markedly as the compacting temperature exceeds the temperature T p , from observations of the cross-sections of compacts; there were only a few voids in the compacts produced from amorphous powders below 46 μm in size at a temperature approximately 30 K above T p . These results suggest that densification of the compact of an amorphous alloy powder by warm consolidation is achieved even at temperatures several tens of kelvins above T p , i.e. well below T p , if, in particular, the size and shape of the powder used and the compacting pressure and time are appropriate.