Activation Energy Of Static Recrystallization Research Articles

Kinetics for static recrystallization after hot working of 0.38C-0.99Cr-0.16Mo steel

The restoration mechanisms for static recrystallization of work-hardened austenite were investigated by using double-pass compression tests performed on medium-carbon steel containing chromium and molybdenum. The softening fraction was defined by 2% offset method. The results show that Avrami exponent of about 0.21 is insensitive to deformation temperature, indicating that the action of steel grade should be considered. The time of 50% recrystallization (t0.5) decreases noteworthily with the increase of deformation temperature. Apparent activation energy for static recrystallization of 195 kJ/mol, which is close to that of vanadium microalloyed steel, is obtained by calculating. The increasing trend of the driving force for recrystallization is opposite to that of the deformation temperature, which is attributed to the number of operative slip system increasing as temperature increasing.

Hot strength and microstructural evolution of 316 stainless steel during simulated multistage deformation by torsion

From a torsional simulation of bar-mill rolling with declining temperature in the range 1200-900°C, constant pass strain (= 0.2), varying strain rate (= 0.1–2.0 s −1) and holding time (= 20 or 40 s) , the hot strength and softening characteristics of worked 316 austenitic stainless steel were determined. In isothermal tests, fractional softening by static recovery and static recrystallization augments with temperature, strain rate and holding time; moreover, it increases in successive passes due to accumulated strain. When temperature is declining, the pass flow stresses rise successively, most notably in the passes below 1100°C. Part of the rise is due to the lower temperature but another part is due to the decreased softening in the intervals especially below 960°C due to inhibition of grain boundary migration by solute segregation. The activation energy in this industrial simulation as calculated by sinh-Arrhenius analysis is lower at 393 kJ.mol than 454 kJ/mol determined under continuous isothermal conditions. Furthermore, while the activation energy for static recrystallization is 364 kJ/mol in declining temperature tests, it is lower than 418 kJ/mol determined in isothermal tests. However, when deformation heating and accumulated strain are considered, it becomes 418 kJ/mol. Metallographic analysis revealed that dynamic recrystallization is operative during the last four passes where only static recovery is operational during the intervals. Moreover, the original grain size is refined from 60 μm to 10 μm.

Bar Mill Torsional Simulation of 304 Stainless Steel

AbstractSimulations of bar mill rolling were performed on worked 304 steel by torsion tests with declining temperature Ti , constant pass strain e i , varying strain rate e i and holding time Ti . In the range 1200–900°C and 2.0–0.1 s−1, the activation energy for the maximum pass flow stresses under these simulated industrial conditions was calculated by sinh-Arrhenius analysis to be 361 kJ/mol which is lower than that determined under continuous isothermal conditions. The fractional softening FS by static restoration declines with decreasing Ti , e i , e i and Ti . In isothermal tests with incomplete recrystallization, FS rises in successive interruptions due to accumulated strain. Under declining T conditions with a pass strain of 0.2, the interpass softening is considerably decreased notably below 1100°C with the result that the pass flow stresses rise regularly as T falls, but faster below 1100°C. The activation energy for static recrystallization was found to be 299 kJ/mol compared to 362 kJ/mol for ...

Static Softening of 63/37 a-Brass Cold and Hot Worked by Tensile Test

Static softening heat treatments after cold and hot working by tension have been performed on 63/37 alpha -brass at 0. 62 to 0. 66 and 0. 68 T//M; the hot deformation temperature lying between 0. 65 and 0. 70 T//M, the strain rate varying between 1. 2 multiplied by 10** minus **4 and 1. 2 multiplied by 10** minus **3 s** minus **1. The static softening treatment of hot worked samples was applied to samples unloaded after deformation in the range of either dynamic recovery or dynamic recrystallization. For the cold worked samples, the stress level before unloading is chosen to be the same as the yield stress at room temperature of samples previously dynamically recovered at high temperature. Curves giving softening levels versus time at different temperatures have been established for the mentioned initial states by mechanical testing. In any case the activation energy of static recrystallization is about 190 kJ/mol.