Microtwin formation in deformed nickel

Abstract

Faults in nickel, which exhibit a fringe contrast behaviour similar to that predicted for stacking faults, are shown to be microtwins. Microtwins are seen to form at stress concentrations prior to crack nucleation during in situ transmission electron microscopy deformation experiments that were performed in vacuum and a hydrogen-gas environment. The presence of environmental hydrogen does not increase the propensity for forming these faults. The formation of the microtwins can be accounted for by the three-layer microtwin mechanism proposed by Mahajan and Chin in 1973.