Modeling gas diffusion into metals with a moving-boundary phase transformation

A fixed-grid, finite-difference model is developed to investigate the movin g-boundary phase transformation that occurs during gas charging or discharg ing from finite specimens. The model is developed in a nondimensional form, and solutions are calculated for plane sheets, cylinders, and spheres. Num erical predictions are compared with existing analytical solutions, as well as experimental data for the beta/alpha transformation of titanium induced by diffusion of oxygen from the surface of a plane sheet. Finally, a param etric study is performed to elucidate the effect of several input parameter s on phase transformation kinetics, and simple empirical relations for the transformation time are developed based on this study.