Study on Austenitization Kinetics of SA508 Gr.3 Steel Based on Isoconversional Method

Abstract

Abstract:The austenitization kinetics of SA508 Gr.3 steel during heating was studied using the isoconversional method combined with continuous thermal dilatometric tests for the first time. The model-free austenitization kinetics was built and the effective activation energy as a function of transformed austenite fraction was determined without transformation models. Then, the corresponding regression validation was carried out. The time-temperature-austenitization (TTA) diagram of SA508 Gr.3 steel, which is very difficult to be obtained using experiment measures, was constructed. Finally, the austenitization kinetics in a more realistic case, i.e., under non-constant heating rates, was predicted, which is found to agree well with the experimental results.

Modified Arrhenius Equation in Materials Science, Chemistry and Biology

“…The austenitization kinetics of SA 508 Gr.3 steel was studied by Luo et al [ 2 ] using an isoconversional method. They described the dependence of the phase transformation rate on temperature using the Arrhenius equation (see Figure 5 in [ 2 ]): where α is the extent of conversion.…”

“…The austenitization kinetics of SA 508 Gr.3 steel was studied by Luo et al [ 2 ] using an isoconversional method. They described the dependence of the phase transformation rate on temperature using the Arrhenius equation (see Figure 5 in [ 2 ]): where α is the extent of conversion. The authors replaced the product Af ( α ) by a new pre-exponential factor B ( α ) and took into account the dependence of effective activation energy on the extent of conversion E ( α ): Results of regression using the modified regression function: are shown in Figure 5 ; the temperature T 0 values (means and standard deviations) for different extents of conversion α are given in Table 1 .…”

“… Arrhenius plot for austenitization of SA 508 Gr.3 steel using isoconversional method [ 2 ] (reduced data) based on the modified Arrhenius equation in the form of Equation (27), with common regression parameter T 0 for all α values. …”

“…According to the Arrhenius equation, the reaction rates at very low temperatures are very small but non-zero. The Arrhenius equation is also used in materials science and biology, for example in describing the kinetics of austenitization [ 2 ], the respiration rate of plant leaves [ 3 ], or the heartbeat rate of terrapins [ 4 ]. In these cases, kinetics at low temperatures are meaningless: austenitization can only take place at temperatures above Ac 1 and many living organisms die or at least their bodily processes stop at body temperatures below freezing.…”

Fast simulation of temperature and phase transitions in directed energy deposition additive manufacturing

“…Where ∆X mar is the phase proportion variation. Usually, the JMAK equation is used for austenitization, which depends on the heating rate [49,50]. However, as heating rates are very high during LMPDED, it seems sufficient to use a KM type interpolation similar to (19).…”