Nano-scaled Ti5Si3 evolution and Strength Enhancement of titanium matrix composites with two-scale architecture via heat treatment

To further improve the mechanical properties of Ti5Si3 and TiBw reinforced Ti6Al4V ((Ti5Si3 + TiBw)/Ti6Al4V) composites with a two-scale network structure, heat treatments were carried out to adjust nano-scaled Ti5Si3 (n-Ti5Si3) particles and matrix characteristics. The fraction of Ti5Si3 particles in the vicinity of first-scale TiBw reinforcements decreases with increasing quenching temperatures. When the quenching temperature is elevated to 1200 °C, the Ti5Si3 particles dissolve and re-solute into the matrix. Both the size and fraction of n-Ti5Si3 particles increase with increasing aging temperatures. The size of n-Ti5Si3 particles in the β phase can be refined from 400-500 nm (as-sintered) to 10-60 nm after heat treatments. The strength of the heat-treated composites was significantly enhanced through heat treatments, when compared with the composites with one-scale architecture and Ti6Al4V alloy. The room temperature compressive strength and high temperature (600 °C) tensile strength can reach 2245 MPa and 880 MPa, respectively. This can be attributed to the heat treatments adjustment of n-Ti5Si3 particles, supersaturated martensite α' phase and two-scale network structure.