Deformation processed IMC-reinforced metal matrix composites

Abstract

The feasibility of utilizing TiB₂-reinforced near-gamma TiAl intermetallic matrix composites (IMCs) as a reinforcing entity within a commercially pure Ti matrix was investigated. IMCs are "ceramic-like" at ambient to moderate temperatures, and “metallic-like" in their deformation behavior above their brittle-to-ductile transition temperature, thus IMCs create opportunities to create unique in-situ composite microstructures otherwise unattainable using conventional ceramic reinforcements.

CP titanium composites reinforced with 20 vol% of near-gamma TiAl IMC were produced by powder blending and densifying via high temperature extrusion deformation processing. The microstructures of the in-situ processed composites were characterized in terms of size, aspect ratio and average spacing of the IMC reinforcement. The microstructural features were correlated to observed mechanical behavior of the composites relative to the unreinforced matrix. The results indicate that the strengthening is derived from microstructural changes within the matrix due to the presence of the IMC particles, and solid solution strengthening due to the diffusion of Al from the reinforcing IMC phase into the Ti matrix. The increase in flow strength due to the former contribution correlates with the inverse square root of the IMC interparticle spacing.