A one-step mechanism for new twinning modes in magnesium and titanium alloys modelled by the obliquity correction of a (58 degrees, a+2b) prototype stretch twin

The {11-22} and {11-26} twinning modes were recently discovered by Ostapovets et al. [Philos. Mag. (2017), 97, 1088-1101] and interpreted as {10-12}-{10-12} double twins formed by the simultaneous action of two twinning shears. Another interpretation is proposed here in which the two conjugate twinning modes result from a one-step mechanism based on a (58 degrees, a + 2b) prototype stretch twin and differ from each other only by their obliquity correction. The results are also compared with the classical theory of twinning and with the Westlake-Rosenbaum model.