The effect of boron addition on brittle-to-ductile transition temperature and its strain rate sensitivity in gamma titanium aluminide

Temperature dependence of tensile properties of Ti-47Al-2Mn-2Nb-0.8TiB(2) a lloy was investigated and brittle-to-ductile transition temperature (T-BD) was evaluated accordingly within the strain rate range from 10(-5) to 10(-1 ) s(-1). T-BD and its strain rate sensitivity in Ti-47Al-2Mn-2Nb- 0.8TiB(2) alloy were compared with those in Ti-47Al-2Mn-2Nb alloy. It is found that the minor addition of 1.0 at% boron reduces T-BD by more than 100 K and tha t T-BD in both alloys shows a positive sensitivity to the strain rate. But the B-doped alloy has a lower BDT activation energy (256 kJ/mol) than that of B-free alloy (324 kJ/mol). The effect of boron on TBD and its strain rat e sensitivity is attributed to the reduction in the grain size. (C) 2000 Kl uwer Academic Publishers.