Rapid self-sustaining consolidation of titanium silicide (Ti5Si3) via transient liquid phase reaction induced by an electric discharge

Abstract

The fabrication of Ti5Si3 in the form of a solid product directly from an elemental 37.5 at.% Si and 62.5 at.% Ti powder mixture was carried out by two different powder metallurgy routes. The first was by uniaxial pressing of the reactant powder mixture with sequent vacuum-sintering, and the second was by electric discharge sintering (EDS) of reactant powder mixture. The pressing process combined with vacuum-sintering produced a porous compact with multi phases of titanium silicide such as Ti5Si3, Ti5Si4, TiSi2, and TiSi, including elemental Ti, which indicated an incomplete phase transformation into Ti5Si3. On the other hand, the EDS induced the phase transformation mostly into Ti5Si3 with a small amount of Ti5Si4 in < 180 mu sec, which had a sequent consolidation into a solid compact with an average crystallite size of 30.4 nm and a lattice parameter of a = 7.42 angstrom and c = 4.91 angstrom. The significantly higher hardness value of the EDS compacts can be the result of the high density and the fine microstructure stemming from the homogeneous dissolution of the elements and the constrained grain growth. The formation of Ti5Si3 solid compact from the stoichiometric Ti and Si powder mixture by EDS can be dominated by the solid to liquid phase transformation mechanism.