SYNTHESIS OF NiAl INTERMETALLIC COMPOUND NANOSIZED POWDERS BY PULSED WIRE DISCHARGE

NiAl nanosized powders were synthesized by pulsed wire discharge (PWD) using twisted Ni and Al wires with various number of turns (N-t). The X-ray diffraction (XRD) patterns indicated that the optimum conditions for synthesized NiAl nanosized powders were usage of a twisted Ni and Al wire with 0.4 turn/mm discharged in N-2 gas. For clarifying the dependence of N-t on the powder purity, waveforms of current, voltage and deposited energy during the discharges were measured. From the waveforms, deposited energy ratio until a voltage peak (K-p), which is an index to evaluate volume fraction of evaporated wire, was calculated. In low K-p conditions, nanoparticles with low composition ratio of Ni (C-Ni) and large particles with high C-Ni were frequently observed. This result indicated that the Ni wire had a high boiling point than that of Al so that unevaporated Ni remained as large liquid droplets in the discharge. Decrease of K-p was thought that the increase of N-t introduced lattice defects by plastic deformation to increase the resistance and to evaporate the wire partially. From the results above, a method to synthesize NiAl intermetallic compound nanosized powders by PWD was successfully developed using Ni and Al twisted wires. In addition, K-p turned out to be important in synthesizing single-phase nanosized powders.