Twinning plays an important role in phase transformations and
can have significant effects on microstructural evolution.
Different roles of twinning in the development of microstructures
during precipitation and phase transformations are reviewed
and illustrated with examples from investigations by
high-resolution electron microscopy, including the effect of
multiple twinning on the development of Ge precipitates in Al-Ge
and Ag-Ge alloys, the twin dissociation of grain boundaries
in Au, the formation of hexagonal Si at twin intersections and
the effect of twin boundaries on the equilibrium shape of Pb
inclusions in Al.
