Abstract
Coarse crystals of martensite can form by the coalescence of thin individual platelets of martensite under appropriate circumstances. Although these coarse grains are essentially single crystals, there exist significant orientation gradients across their dimensions. It is demonstrated that these gradients arise because of the plasticity induced in austenite due to the transformation strain associated with martensite growth. The resulting localised change in austenite orientation is then inherited by the new martensite growth, which consumes the deformed austenite.
The authors are grateful to the technical staff at the NCNT-POSTECH for help with the TEM and FIB work, and to J. H. Kang and J. H. Ryu for discussions. The present work was funded by the Steel Innovation Program of POSCO and the World Class University under programme no. R32-2008-000-10147-0 of the National Research Foundation of Korea.