The role of twin boundaries (TBs) in the dynamic recrystallization (DRX) of Ni-30Cu (Monel400) was investigated through hot compression tests in the temperature interval of 750–1150 °C and strain rate of 0.01 s−1. Electron Back Scattered Diffraction (EBSD) analysis showed that DRX at 750 and 950 °C was limited to bulging and sparse nucleation on random high angle grain boundaries (HAGBs) while the primary coherent twin boundaries (TBs), with a length density of 55% in the starting microstructure, did not take part in the bulging process before conversion into HAGBs. The sluggish DRX was therefore attributed to the necessary conversion of primary TBs into HAGBs. The investigation also revealed that a new variant of TBs formed behind the protruding grain boundaries separated the bulges from the parent grains, indicating that unlike primary TBs, the newly formed TBs contributed to the occurrence of DRX. The formation of the new TBs was related to the dissociation of well-developed subgrains and the migration of random HAGBs. A mechanism for the occurrence of DRX in hot deformed Monel 400 is proposed that takes into account the contribution from the new TBs.

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