Phase Formation in the SHS of a Ti–B Mixture with the Addition of Si3N4

Abstract

The structure and phase composition of a material obtained via SHS in the combustion of a 87% Ti + 13% B powder mixture with the addition of Si3N4 is under study. The phase formation mechanism in this system is discussed. It is established that the material contains 64% of the TiB phase with an orthorhombic structure and 36% of the solid boron solution in titanium ( $$\alpha$$ -Ti[B]). The boron content in $$\alpha$$ -Ti significantly exceeds its equilibrium content according to a state diagram. In the case of combustion of an 87% Ti + 13% B mixture with the addition of 5% Si3N4, the finite product contains TiB, $$\alpha$$ -Ti[B], TiB2, and Ti5Si3 phase. The TiB phase is present in the form of two modifications: orthorhombic and cubic. The completeness of a structural transition of the cubic modification of TiB into an orthorhombic one is determined by the cooling rate of a sample. It is assumed that the combustion of the mixture with the addition of Si3N4 forms the dispersed discharges of TiN, which are the crystallization centers of cubic TiB.