Preparation of TiB2-20 Wt Pct MoSi2 Composite Material by Mechanochemical Synthesis and Spark Plasma Sintering

Abstract

The mechanosynthesis process of composite powders for the preparation of a TiB2-20 wt pct MoSi2 composite material from reaction mixtures Ti + B + Mo + Si and Ti + B + MoSi2 in an argon atmosphere has been investigated. Synthesis proceeds according to mechanically stimulated reactions, and, in both cases, ultradisperse composite powders, along with the main phases, contain traces of lower silicides. The mathematical modeling of the distribution of interparticle contacts in the mixtures during solid-phase interaction has revealed a good agreement between the calculated and experimental data of mechanosynthesis. Spark plasma sintering in nonlinear regimes with a sequential increase in the sintering pressure from 6 MPa up to 50 MPa, accompanied by a decrease in the heating rate from 150 °C/min down to 50 °C/min, enables us to reduce the sintering temperature down to 1550 °C and obtain a dense composite with a mean size of TiB2 grains of about 200 nm. The TiB2-20 wt pct MoSi2 composite sintered at 1550 °C surpasses the composite sintered at 1750 °C in Vickers hardness (27.5 ± 3.2 GPa and 24.6 ± 2.2 GPa, respectively) but ranks below it in bending strength (480 ± 32 MPa and 571 ± 24 MPa, respectively).