Synthesis of Dual Two-Phase Ni₃Al-Ni₃V Intermetallic Alloys Containing Nb by Pulse Current Sintering

Abstract

A dual two-phase Ni₃Al-Ni₃V intermetallic alloy with a nominal composition of Ni_75.0Al_7.5V_15.0Nb_2.5 (at%) doped with 50 mass ppm boron was synthesized by the powder metallurgy process using elemental powders. Raw powder mixture was sintered at temperatures from 1073 K to 1373 K by the pulse current sintering method and then annealed in a vacuum at 1553 K for 3 h. The dual two-phase intermetallic alloy whose microstructure exhibits the cuboidal primary Ni₃Al phase and the surrounding channel region composed of Ni₃Al and Ni₃V phases, and contains neither voids nor intermediate products were obtained by sintering at a high temperature of 1373 K and by subsequent annealing at 1553 K. Also, the well synthesized and annealed samples showed finer grain sizes, i.e., about 30 μm than the cast alloys fabricated by the ingot metallurgy process. The hardness of the synthesized samples increased with increasing sintering temperature and also by the subsequent annealing at 1553 K.