Deformation twinning at aluminum crack tips
S. Hai and E. B. Tadmor
Acta Materialia, 51, 117-131 (2003).

ABSTRACT
Recent experimental evidence has shown that
even fcc materials that are not normally associated with deformation twinning,
such as aluminum, will twin given a sufficiently high stress concentration such
as at a crack tip. In this paper we present a computational study of the
atomic structures that form at the tips of atomically-sharp cracks in aluminum
single crystals under loading. The simulations were carried out using the
quasicontinuum method - a mixed continuum and atomistic approach.  A variety
of loading modes and orientations were examined. It was found that for certain
combinations of loading mode and orientation, deformation twinning does occur
at aluminum crack tips in agreement with experimental observation.
For other configurations, either dislocation emission or in one case
the formation of an intrinsic-extrinsic fault pair was observed.
It was also found that the response at the crack tip can depend on the crack-tip
morphology in addition to the applied loading and crystallographic orientation.