Influence of Thermal Aging on Tensile-Plastic Flow Behavior of Indian Steel RAFM (F82H)

Influence of thermal aging (873 K, 5000 h) on microstructure and tensile-plastic flow behavior of normalized and tempered (N&T) 1.4W - 0.06Ta IN-RAFM steel is investigated. The Ludwigson and Voce equations are used to elucidate the tensile-plastic flow response of the IN-RAFM steel over a wide temperature range of 298 - 873 K. Both the yield strength and the tensile strength are fitted by the initial stress and saturation stress, respectively, as per the Voce constitutive equation. The strain hardening exponent increases under aging due to the increase in the work hardening capability of the aged steel, while the strain hardening coefficient decreases with the aging. TEM specimens extracted from a tensile tested sample are used to correlate the formation and the movement of dislocation debris in the structure of both N&T and thermally aged steel. The absolute value of nv decreases due to the aging exhibiting a two-stage behavior. The acceleration of the recovery process is lower at the high temperature in the steel subjected to thermal aging as compared to the N&T steel. The Voce relation is used successfully to predict the yield stress and the ultimate tensile strength of both thermally aged and N&T IN-RAFM steel at different temperatures.