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Abstract
A comprehensive mechanism-based crystallographic constitutive model has been developed for L12-structured Ni3Al-based intermetallic single crystals. This model represents the unusual thermomechanical behaviours of Ni3Al, such as the anomalous temperature dependence of both the flow stress and strain-hardening rate (SHR), the strain dependence of these anomalous behaviours and an orientation-dependent tension–compression asymmetry. The model framework was based on two major contributions to plastic flow, namely the repeated cross-slip exhaustion and athermal defeat of screw-character dislocations, and the motion of macro-kinks (MKs). The contribution of irreversible obstacle storage was incorporated into the constitutive formulations as a resistance against the glide of MKs. The model was implemented in a finite element method numerical framework, and the simulation results showed qualitative agreement with experimental observations.
§This paper is dedicated to Dr. Peter M. Hazzledine (1940–2005), one of few pioneers who brought the unique dislocation behaviour of L12 intermetallics to scientific attention.
Acknowledgements
The present work was supported by the U.S. 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 contract #FA8650-04-D-5233 F33615-96-C-5258 and F33615-01-5214. The authors acknowledge fruitful discussion with Drs. S. Rao, UES, Inc, and C. Woodward, AFRL/MLLM. The computations described in this study were performed using computer resources at the Ohio Supercomputer Centre (grant #'s PAS0191 and PAS0647) with the collaboration of Professors S. Ghosh and G. Daehn of The Ohio State University.
Notes
§This paper is dedicated to Dr. Peter M. Hazzledine (1940–2005), one of few pioneers who brought the unique dislocation behaviour of L12 intermetallics to scientific attention.
