A Deformation Mechanism Map for Incoloy 800H Optimized Using the Genetic Algorithm

A total of fifty-eight Incoloy 800H samples were creep tested between temperatures of 1023 K and 1293 K, stresses of 14.1 to 105 MPa, and average grain sizes of 87.7 to 315 mu m. Combined with data obtained by the National Institute for Materials Science (NIMS), a deformation mechanism map (DMM) for Incoloy 800H was produced. Optimization of the fit of the constitutive creep equations to the experimental data was performed using a global search iterative numerical optimization tool called a genetic algorithm (GA). It was found that the data were well represented by both high-temperature and low-temperature power-law creep mechanisms, but the extent of the influence of diffusion-based creep mechanisms, most specifically Coble creep, will require further investigation. A training and test method was performed to validate the solution and to test the extrapolability of the dataset. It was determined that the extrapolability of the data in all directions of the DMM was generally low.