Tensile flow and work-hardening behavior of a Ti-modified austenitic stainless steel

Abstract

The flow-stress data of a 15Cr-15Ni-2.2Mo-Ti modified austenitic stainless steel in the temperature range 300 to 1023 K was analyzed in terms of Ludwigson and Voce equations. The parameters of these equations were critically examined with respect to the effect of Ti/C ratio and test temperature. It was found that the Ludwigson equation described the flow behavior adequately up to the test temperature of 923 K, whereas the Voce equation could be employed in the full temperature range. The peaks/plateaus observed in the variation of these parameters as a function of temperature in the intermediate temperature range have been identified as one of the manifestations of dynamic strain aging (DSA). Also, the variation of these parameters with temperature clearly could bring out the different domains of DSA observed in this alloy. The work-hardening analysis of the flow-stress data revealed that in the DSA regime, the onset of stage III hardening is athermal.

Comparative tensile flow and work hardening behaviour of thin section and forged thick section 9Cr–1Mo ferritic steel in the framework of Voce equation and Kocks–Mecking approach

“…8) and hr-r and in the variations of work hardening parameters associated with Voce equation (Figs. 9-11) and K-M approach with temperature observed for plate and tubeplate forging are in agreement with those reported for ferritic and austenitic steels [11][12][13][14][15]24].…”

“…n V describes the rate at which the stress from its initial value tends to reach steady state or saturation stress value [6]. The applicability of Voce relationship for describing stress-strain behaviour useful for engineering applications has been demonstrated for ferritic, pearlitic-ferritic and austenitic stainless steels [11][12][13][14][15]. In the Kocks-Mecking phenomenological approach [7,8], the evolution of dislocation structure with strain at constant strain rate is assumed as a single structural parameter responsible for plastic flow.…”

Work-Hardening Behavior of the Ni-Fe Based Superalloy IN718

“…[30] This stage has been attributed to stabilization of the plastic strain rate associated with the dislocation source density in the austenitic stainless steels. [21,30] The transient stage observed here is different from stage I in the case of single crystals for which the h values are so narrow that it is almost reduced to a starting baseline point. In fact, in polycrystals the transient stage occurs only at low initial plastic strain, the value of which depends on the stacking fault energy (SFE).…”

“…Ludwigson and Voce relationships are known to describe the flow behavior of materials, exhibiting similar nonlinear behavior of log r vs log e p , such as Nimonic 263 and austenitic stainless steels. [20][21][22] The Ludwigson equation is simply a best-fit mathematical model based on the deviation of stress at low strain from that resulting from extrapolation of the linear high strain data. The physical interpretation of flow curve parameters has been given earlier.…”

“…The various stages of hardening observed in this article are consistent with those reported for other metals and alloys. [21,[27][28][29][30][31][32] In the transient stage, and with an increase in stress, both dislocation velocity and mobile dislocation density increase, leading to rapid rise in plastic strain rate immediately after the elastic limit. [30] This stage has been attributed to stabilization of the plastic strain rate associated with the dislocation source density in the austenitic stainless steels.…”