Precipitation of β particles in a fully lamellar Ti-47Al-2Nb-1Mn-0.5W-0.5Mo-0.2Si (at.%) alloy

摘要

The precipitation of β (B2) particles at intermediate temperatures, between 760°C and 1050°C, is investigated in a fully lamellar TiAl-WMoSi alloy. The β particles, having a thin-plate shape, usually precipitate on the α2 side of α2/γ interfaces at low aging temperatures in an uneven two-dimensional growth mode. While those formed at higher aging temperatures, growing extensively within the α2 plate and into the adjacent γ lamellae, have an ellipsoid shape. The growth of β particles at low aging temperatures yields an activation energy of about 366 kJ/mol. It is suggested that at low aging temperatures the growth of β particles proceeds via an α2 → β precipitation process controlled by diffusion of W and Mo along the β/α2 and β/γ interfaces.