The effect of twinning interactions up to the seventh generation on the evolution of microstructure
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The investigation reported here extends the conventional approach to the study of the interface network, by consideration of Σ3 n values up to n = 7 in alpha-brass. All 24 crystallographically-related solutions for each Σ3 n misorientation are included. The study has shown that multiple annealing twinning does not result in aggregation of higher Σ3 n values and concomitant reduction in Σ3s. When a 5° deviation from the exact reference misorientation was used, 20% and 27% of the interface length was Σ729 and Σ2187 respectively. This is a consequence of the increasing number of Σ3 n variants as n increases. Interactions of Σ3 n , often Σ3 + Σ3 n ↔Σ3 n +1, were observed frequently in the microstructure. The prevalence of boundaries near to high order Σ3 n attests their importance in the evolution of microstructure. Analysis of all 24 equivalent solutions for Σ3 n boundaries has shown that approximately half of these are misoriented on \(\langle 110\rangle\), compared to less than one-third on \(\langle 111\rangle\). The promulgation of Σ3 n boundaries via multiple twinning interaction events promotes and increases the proportion of \(\langle 110\rangle\) tilt boundaries, and to a lesser extent \(\langle 111\rangle\) boundaries. These misorientations have been shown to be associated with low-index boundary planes, and therefore multiple twinning is instrumental in promoting these ‘special’ planes.
KeywordsTriple Junction Interface Network Coincidence Site Lattice Twist Boundary Tilt Boundary
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