Abstract :
This paper reports an experimental investigation on the effect of multiple twinning on the
interface population in two low stacking-fault alloys. This is an important topic for grain
boundary engineering because annealing twinning is the indirect cause of improved
intergranular corrosion resistance in this class of materials. Proportions of 3n (n = 1–5)
boundaries were analysed in both a brass specimen and a superalloy specimen where the
boundaries had been processed so as to be very mobile and less mobile respectively. When
3 twin boundaries (as distinct from 3 grain boundaries) are discounted, the 3n
distribution for both specimens had a peak at 9, because 3 + 9 → 3 occurs more
frequently than 3+ 9 → 27. The distributions and reactions between various 3n values
are described and discussed in detail. A novel trace analysis procedure is used to extract
information from 3 boundaries to decide whether or not they are annealing twins, and so
provide a convenient means to assess proportions of twin and non-twin 3s. The data show
unambiguously that a significant proportion of 3s are not on {111}, and these boundaries
have on average higher angular deviations from the exact 3 reference misorientation than
do other 3s. A population of 3s which were vicinal to annealing twins were also
recorded. These data support the contention that profuse annealing twinning produces
concurrently many not-twin 3s, which are pivotal in grain boundary engineering.
C 2005 Springer Science + Business Media, Inc.
