Stress-assisted nucleation and growth of γ″ and γ′ precipitates in a Cu–1.2 wt%Be–0.1 wt%Co alloy aged at 320°C

Growth kinetics of ellipsoidal ω-precipitates in a Ti–20 wt%Mo alloy under compressive stress

“…Similar stress-oriented precipitation was observed for the disk-shaped GP zones in a Cu-0.9Be single crystal [6], and the plate-shaped γ′′ phase in a Cu-1.2Be-0.1Co alloy [7].…”

“…Many investigators have examined the effects of applied external stress on the precipitation of plate-shaped second phases or disk-shaped Guinier-Preston (GP) zones in Al−Cu [1−4], Al−Zn−Mg [5], and Cu−Be [6,7] alloys for many decades. For example, Eto et al [2] investigated the effect of external stress on the precipitation of disk-shaped GP zones and plate-shaped θ' phase in single crystals of an Al−3.71Cu alloy (All compositions in this text are expressed by weight per cent, wt%).…”

Effect of external stress on nucleation of ellipsoidal ω precipitates in a Ti–20 wt% Mo alloy

“…The structure of the ω phase in an aged Ti-14Mo alloy is hexagonal with a=0.2820 nm and c=0.4606 nm [9]. Since the ω precipitates have an ellipsoidal shape slightly elongated along <111> β of the β-Ti matrix [10], in contrast to the disk-shaped GP zones and γ" phase in Cu-Be alloys [5,6] and the disk-shaped GP [1] zones and θ' phase in Al-Cu alloys [1][2][3][4], it is interesting to examine how crystallographically-equivalent four ω variants are formed under an applied external stress. We have found the stress-oriented nucleation of the ω precipitates, which depends on the sense of the applied stress, and furthermore found the promotion of the nucleation of ω precipitates under an applied tensile stress but almost no effect of an applied compressive stress on the nucleation, as will be shown later.…”

“…3c that aging under tension and compression accelerates the growth of the precipitates. The average sizes r and l of ω precipitates in the specimen FA at 300 °C follow a parabolic growth law ( and ∝ 1 2 ), whereas aging at 300 °C under tension generates an increase in precipitate size that is linear with t. Consequently, while the growth of ω precipitates is governed by the diffusion of Mo atoms in ω precipitates from the interface between the β-Ti 7 matrix and the ω precipitates to the β-Ti matrix [12], precipitate growth is instead interface-controlled under tensile stress [6]. The result of a more detailed investigation of this phenomenon will be reported in a future paper.…”

“…In addition, the misfit strains, ε 11 =ε 22 and ε 33 , of the GP zone in directions, respectively, parallel and perpendicular to the plate plane have been estimated from measurements of the length change and lattice parameter during aging. Moreover, Monzen et al [6] have examined the effects of an external stress on the nucleation and growth of disk-shaped γ" phase for a Cu-1.2Be-0.1Co alloy aged at 320°C. The metastable γ" phase is composed of alternate Be and Cu matrix layers parallel to the {100} α planes.…”