| The deformation induced martensitic transformation phenomena in 304 stainless steel have been investigated in this study in relation to the inelastic deformation theory. A new kinetics equation for deformation induced martensitic transformation has been formulated based on the inelastic deformation theory as f/f_s=1-exp(-βεⁿ) with the parameter β characterizing the stability of austenite, n denoting a deformation mode parameter, and f_s the saturation value of transformed martensites. The value of n was determined as n = 2.2 for this steel, while the stability parameter β was found to be inversely proportional to the test temperature. Consequently the M_d temperature, above which martensitic transformation can not occur regardless. of the amount of plastic deformation, can be determined indirectly as the temperature with β=0. The true stress-true strain curves at lower temperatures showed low work hardening rate region followed by rapid increase in work hardening rate, while the curves at near room temperature showed a continuously decreasing low work hardening rate. As the test temperature increased, the maximum transformation rate (df/dε) decreased, but the inelastic strain Corresponding to the peak transformation rate increased resulting in a substantial ductility enhancement. |
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