Experimental assessment of the contribution of annealing twins to CSL distributions in FCC materials

Abstract

The correlation between CSL distributions and annealing twins was assessed for a wide range of fcc materials using the electron backscattered diffraction technique. The maximum frequency of twin boundaries determined experimentally (≈61%) is consistent with the previously proposed theoretical limit of 2 3 . The frequency of special grain boundaries (∑1–∑29) was found to lie within limits defined by (1) an upper limit based upon twin energetics leading to the creation of additional special grain boundaries, and (2) a lower limit arising from isolated twinning events. Moreover, the occurrence of ∑3 n grain boundaries is attributed to the geometric interaction of twin related variants. Its effect is shown to be minimal at low frequencies of ∑3, but significantly higher at twin densities greater than approximately 40%. These experimental observations are consistent with the previously proposed model of Palumbo et al.[1]which predicts a ‘Twin-Limited Microstructure’ consisting entirely of special grain boundaries.