Design of powder metallurgy titanium alloys and composites

Low cost and good performance are two major factors virtually important for Ti alloy development. In this paper, we have studied the effects of alloying elements, thermo-mechanical treatment and particle reinforcement on microstructures and mechanical properties of powder metallurgy (PM) Ti alloys and their composites. Our results indicate that low cost PM Ti alloys and their composites with attractive properties can be fabricated through a single compaction-sintering process, although secondary treatments are required for high performance applications. Three new PM Ti alloys and one TiC/Ti composite of high performance are developed, and new design principles are also proposed. For design of PM Ti alloys, addition of alloying elements has the beneficial effect of enhanced sintering and/or improved mechanical properties. For example, Fe element accelerates the sintering process, Mo and Al are good candidates for solution strengthening, and rare earth elements effectively increase the material ductility by scavenging oxygen from the Ti matrix. For the design of Ti-based composites, in situ formation of strengthening particles and solid solution hardening of the matrix both should be considered simultaneously for alloy development. Cr3C2 is found to be a very suitable additive for processing particle reinforced Ti composites.