Modeling interstitial diffusion controlled twinning in alpha titanium during low-temperature creep

Solid solution strengthening of hexagonal titanium alloys: Restoring forces and stacking faults calculated from first principles

“…It should be emphasized that increased number of NEB images does not change the energy gradient or USFE, indicating the absence of any energetically important intermediate O positions. This new phenomenon is similar to model presented by Oberson et al [49,50] who showed that lattice reorientation during a-and b-Ti twining eliminates octahedral sites leading to O diffusion. An additional nonequilibrium interstitial site in prism SF was also illustrated by M. Ghazisaeidi et al [18].…”

The effect of ageing on microstructure and mechanical properties of powder Ti–5Al–5Mo–5V–1Cr–1Fe alloy

“…Solid state diffusion is the mechanism responsible for mass transfer resulting in the observed compositional difference in the phases with the ageing time. The effective diffusion distance of an element can be estimated by the following equation [37]:…”

Time Dependent Twinning and the Role of Oxygen in the Low Temperature (<0.25 Tm) Creep Behavior of Alpha Titanium Alloys

“…Ankem et al first noted that oxygen (O), which has high solubility in -Ti [4], may interfere with twin growth and produce the observed time-dependence [2]. Subsequent experimental work coupled with crystallographic/hard-sphere modeling further suggests that O interstitials could interfere with atomic shuffling during twinning in -Ti [5,6], however the measured activation barrier for twinning of 0.684 eV [5] is not in agreement with the measured activation barrier for O diffusion in bulk -Ti of 1.75 ± 0.52 eV [7]. Part of this discrepancy could be due to complicated interactions between O interstitials and deformation twins that are not captured by hard-sphere modeling and it therefore necessary to study the effects of deformation twins on the thermodynamic and kinetic properties of O.…”

“…It is not possible for atoms to move from the matrix positions to the twinned positions via a homogeneous shear; instead, a combination of shear and shuffle is required [11]. During the shuffling step for twin growth, some Ti atoms must move across the interstitial octahedral sites where O is known to exist [5,6]. Experimental evidence demonstrates the significance of twin-O interactions in determining mechanical properties in some Ti alloys.…”