Effects of boron, carbon and silicon additions on microstructure and properties of a Ti15Mo based beta titanium alloy

Additions of boron, carbon, and silicon have been made to a series of Ti-15Mo based beta titanium alloys prepared by plasma are melting and subjected to various processing and characterisation techniques. The purpose of these additions was to investigate their grain refining effect in the as cast, as forged, and heat treated states. The boron and carbon additions promoted dendritic solidification. Boride and carbide particles were present in the interdendritic regions. However, a fully equiaxed fine grained structure could not be obtained even at the highest levels of addition (1.0 wt-%), These additions resulted in substantial microstructural refinement after forging and the particles stimulated the nucleation of recrystallised grains. Significant retardation of grain growth was observed after solution treatment and attributed to the Zener pinning effects of the boride and carbide particles. Despite the microstructural refinement, the ductility of the alloys containing boron and carbon was severely impaired. (C) 2001 IoM Communications Ltd.