2023 年 64 巻 9 号 p. 2246-2253
In this study, the effect of the initial phases of the Si-bearing near-α titanium alloy Ti–6Al–2.75Sn–4Zr–0.4Mo–0.45Si (Ti-1100) on Vickers microhardness during aging at 600°C from 5 min to 42 days was investigated by transmission electron microscopy. The initial phases included α′ martensite and α phases. The variation in the hardness of the specimen with the initial α′ martensite phase occurred in the following order: the decrease caused by dislocation recovery, the increase caused by silicide precipitation, the decrease caused by silicide coarsening, and the increase caused by α2 precipitation. As for the initial α phase, hardness initially decreased and then increased because of dislocation recovery and silicide/α2 precipitation, respectively. The difference in age-hardening behavior resulted from the difference between the dislocation amounts in the two initial phases. Silicide precipitation was promoted by dislocations, whereas α2 precipitation occurred via homogeneous nucleation irrespective of the dislocations.
