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 degrees 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 beta 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 degrees 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 alpha' phase and two-scale network structure.