Influence of transformation temperature on microtexture formation associated with α precipitation at β grain boundaries in a β metastable titanium alloy

Abstract

The influence of transformation temperature on microtexture development associated with a precipitation at b/b grain boundaries (GB) in the near-b Ti17 alloy was studied using electron backscatter diffraction and considering isothermal treatments. For the alloy studied and the temperature range considered, decreasing the transformation temperature decreased the local microtexture strength within each prior b grain because of a larger number of a WGB colonies (standing for a Widmanstätten GB) formed per b grain, each colony increasing by one the number of a orientations inside each prior b grain. This larger number of a WGB colonies was a consequence of faster formation along b/b GB of their precursors, the allotriomorphic a GB grains (standing for a-GB) at lower transformation temperatures, as evidenced by detailed examination of the first stages of a GB formation. a GB crystallographic orientations frequently followed a variant selection (VS) criterion based on the alignment of (0 1 1)b//(0 0 0 1)a GB //(0 1 1)b. From a statistically relevant number of observations, VS was found to be more frequent at a lower transformation duration and a lower temperature, but the effect was not significant enough to influence the final a microtexture, considered at the scale of one prior b grain. a GB grains that followed the VS criterion emitted two a WGB colonies on either side of the b/b GB more frequently than those with no particular orientation.

Influence of β‐Forging on Texture Development In Ti 6246 Alloy

“…In their work, Salib et al, pointed out that the GB nucleation starts at a triple or quadruple grains junction and then grow most frequently along only one grain boundary, according the BOR. There is competition between grain boundaries link at a same grains junction (triple or quadruple) [16]. These criteria totally agree with the growth of the GB observed on this area.…”

“…As it is widely report in the literature. Grain boundaries are not always covered by GB and several nucleation criteria have been proposed [14][15][16]. According to Bhattacharyya et al, GB can nucleates between two grains when they have a 110 pole in common.…”

Influence of phase transformation kinetics on the formation of α in a β-quenched Ti–5Al–5Mo–5V–3Cr–1Zr alloy

“…The transformation of a from b begins through the formation of a at the b grain boundaries (a GB ) and follows by the growth of Widmanstätten a colonies (a WGB ) from a GB /b interfaces by depletion of b stabilizer elements (e.g. vanadium) [15,25,75]. The present results show that the direct formation of a via b ?…”

“…The characteristics of the a phase, i.e. its morphology, volume fraction, size and distribution, are strongly influenced by the phase transformation kinetics during thermal treatments [12][13][14][15]. Although important insights regarding the formation of a in metastable b titanium alloys have been reported, most studies are focused on isothermal ageing (e.g.…”

Microstructure and transformation texture evolution during α precipitation in polycrystalline α/β titanium alloys – A simulation study

“…VS of GB a arises from differences in orientation relationships of GB a with respect to both adjacent b grains and in habit plane orientations of GB a relative to the grain boundary inclination among all 12 candidate GB a variants. Some empirical rules have been proposed to explain the effect of these grain boundary parameters on VS of GB a [55,[67][68][69]. Nevertheless, not a single rule or even a combination of different rules is general, i.e., they are not always followed and could all be violated [24,67].…”