EVALUATION OF THE INTRINSIC AND EXTRINSIC FRACTURE BEHAVIOR OF IRON ALUMINIDES
In this paper, we first present the status of our computational modeling study of the thermal expansion coefficient of Fe{sub 3}Al over a wide range of temperature and evaluate its dependence on selected additives. This will be accomplished by applying an isobaric Monte Carlo technique. The required total energy of the sample will be computed by using a tight-binding (TB) method that allows us to significantly increase the size of the computational data base without reducing the accuracy of the calculations. The parameters of the TB Hamiltonian are fitted to reproduce the band structure obtained by our quantum mechanical full-potential LMTO calculations. The combination of the three methods mentioned above creates an effective approach to the computation of the physical properties of the transition-metal aluminides and it can be extended to alloys with more than two components. At present, we are using a simplified approach for a first-round of results; and as a test of the simplified approach, have obtained excellent agreement with experiment for aluminum. Our previous experimental results showed that, because of their smaller grain size, FA-187 and FA-189 are extrinsically more susceptible to environmental embrittlement than FA-186 under low strain loading condition. To further investigate the grain boundary size effect as related to the susceptibility of hydrogen embrittlement, we conducted comparative finite element modeling simulations of initial intergranular fracture of two iron aluminides (FA186 and FA189) due to hydrogen embrittlement. Sequentially coupled stress and mass diffusion analyses are carried out to determine crack-tip stress state and the extent of hydrogen diffusion at the crack tip region, and a proper failure criteria is then adopted to simulate the intergranular fracture. Good qualitative agreement between the modeling predictions and experimental results is observed.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- AC05-00OR22725
- OSTI ID:
- 814281
- Report Number(s):
- ORNL/SUB/95-ST547/04; TRN: US200317%%143
- Resource Relation:
- Other Information: PBD: 16 May 2000
- Country of Publication:
- United States
- Language:
- English
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EVALUATION OF THE INTRINSIC AND EXTRINSIC FRACTURE BEHAVIOR OF IRON ALUMINIDES
Evaluation of the Intrinsic and Extrinsic Fracture Behavior of Iron Aluminides