Spark Plasma Sintering and Microstructural Characterization of Nb–Cr Eutectic Alloy

Abstract

Bulk NbCr2 Laves phase composites are fabricated via spark plasma sintering using coarse Cr and Nb powders. The sintering behavior and phase morphological evolution of the Nb–Cr eutectic alloy along the sintering temperature are investigated. The results show that the microstructures of the samples sintered at different temperatures consist of Nbss, Crss, and NbCr2 Laves phase without any formation of eutectics. The phase transformation and microstructural evolution are analyzed by considering the inhomogeneous temperature distribution and the accelerated atomic diffusion induced by the applied pulsed electric current. While the absence of eutectic and the grain refinement of NbCr2 Laves phase are mainly attributed to the in situ precipitation from the supersaturated Nb solid solution and the transient thermal compressive stress caused by the nonsynchronous of temperature increment and thermal expansion during spark plasma sintering.