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Abstract
The two-step (T 1 and T 2) deformation behaviour of Ni3Al-based single crystals was modelled under the framework of a new constitutive model proposed by Y.S. Choi, D.M. Dimiduk, M.D. Uchic, et al. [Phil. Mag. 87 1939 (2007)]. A new set of formulations and criteria, which identify thermally reversible and irreversible components of the constitutive variables and define the relative significance of those components, was developed and implemented within the new constitutive framework. The simulation results well captured the general qualitative trends of the flow behaviour upon re-straining at T 2 after pre-straining at T 1 for both T 1 > T 2 and T 1 < T 2. Modelling results suggested that the dislocation substructures generated at T 1 need to be treated as partially or fully transferable to plastic flow at T 2, at least through the early stage of re-straining, to capture all major pre-strain effects. In particular, the large strengthening effect at T 2 for even a few percent of pre-strain at T 1 was obtainable only by controlling the availability of mobile dislocations and sources at T 2.
Acknowledgements
This study was supported by the US Defense Advanced Research Projects Agency and the Air Force Office of Scientific Research. YSC and TAP acknowledge support from the Materials and Manufacturing Directorate under the contract # FA8650-04-D-5233. The authors acknowledge fruitful discussion with Dr S. Rao of UES, Inc. and Dr C. Woodward of AFRL/MLLM. The computations described in this study were performed using computer resources at the Ohio Supercomputer Centre (grant #s PAS0647 and PAS0191) with the collaboration of Professor G. Daehn and Professor S. Ghosh of Ohio State University.