Nucleation of Bar-Like α-Precipitates in a Ti-20 mass%Mo Alloy under External Stress

The effects of external stress on the nucleation of bar-like alpha-precipitates were examined for a Ti-20 mass%Mo alloy aged at 773 K. Overall, the application of a tensile stress accelerated the nucleation of alpha-precipitates, whereas a compressive stress did not significantly affect it. Specifically, the tensile stress promoted the formation of alpha-precipitates when the misfit strain epsilon(M) of the precipitates along the loading direction was greater than 0; however, it did not significantly affect the precipitate nucleation in ease where epsilon(M) < 0. In contrast, the compressive stress promoted the precipitate nucleation when epsilon(M) < 0 and did not significantly influence it when epsilon(M) > 0. The average misfit strain of the alpha-precipitate was estimated as 0.019 from measurements of length change and lattice parameter of the beta-Ti matrix.