Effect of heat treatment on structure formation of pre-compacted titanium and silicon powder mixtures

Metal matrix titanium composites reinforced with a silicide phase are produced by hot compaction and subsequent high-temperature annealing of titanium and 5 wt.% silicon powder mixtures. An X‑ray diffraction analysis and optical and scanning electron microscopy are used to study their microstructure and the elemental and phase compositions. The strength properties of the annealed samples are evaluated by measuring the microhardness. It is found out that the annealing temperature affects the microstructure, the phase composition and the microhardness of the powder compacts. An increase in the annealing temperature within the range of 800–1200 °C results in the completed silicon and titanium reaction and the formation of Ti₅Si₃ silicide, which constitute a net-like structure along the boundaries of the titanium grains. The structure evolution with the increasing temperature results in a progressive hardness increase. In order to increase the strength properties, the hardening phase distribution homogeneity and a more uniform material density, a fine titanium powder and a high hot compaction pressure are required.