Observation of partial dislocations on a coherent twin boundary

Dislocations observed on a coherent twin boundary in an austenitic stainless steel are shown to be pairs of the Shockley partial α/6 ⟨ 211 ⟩ type. The twin boundary stacking-fault energy is measured from the separation (∼ 1400 Å) of the partials as ∼ 1 erg cm−2. This is much lower than the reported matrix stacking-fault energy (∼ 60 erg cm−2) and is attributed to the stacking sequence of atom planes across a coherent twin. The significance of this observation is discussed.