Structure and Phase Composition of SHS Products in Powder Mixtures of Titanium, Carbon, and Aluminum

Abstract

TiC + Al binder metal-matrix composites are fabricated by self-propagating high-temperature synthesis (SHS) in reaction power mixtures of titanium, carbon (ash), and aluminum. It is established that stable combustion in a steady wave mode is possible with a content up to 50 wt % aluminum powder in a reaction mixture. Crushing of synthesized loose cakes and subsequent sieve scattering gave composite powders with a cloddy shape close to equilibrium. This shape is favorable for good looseness, which is necessary when using powders for surfacing and sputtering of wear-resistant coatings. Synthesis products are investigated by scanning electron microscopy and X-ray structural (XRS) and energy-dispersive X-ray (EDX) analysis. It is established that the average size of carbide inclusions in the composite structure decreases monotonically with an increase in the content of the aluminum powder inert in the thermal aspect in reaction mixtures. The lattice parameter of titanium carbide determined by the XRS method turned out much smaller than known values for equiatomic-composition carbide. Herewith, no dependence of the lattice parameter on the aluminum content is found for composites. Carbide inclusions in the composite structure are investigated by the EDX method, and it is established that the titanium content corresponds to its concentration in equiatomic-composition carbide. In addition to titanium and carbon, carbide contains up to 2.5 wt % dissolved aluminum, which can affect the carbide lattice parameter.