Papers by Keyword: Dynamic Recrystallization (DRX)

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Authors: Lei Chen, Xiao Cong Ma, Ming Jia Wang, Hua Gui Huang
Abstract: The flow behavior and microstructural evolution of an as-wrought duplex stainless steel has been investigated by Gleeble-3500 thermal-mechanical simulator within the temperature range of 950-1200°C and the strain rate range of 0.1-10s-1. The flow curves exhibited a peak stress characteristic followed by dynamic softening and the strain for appearance of steady stress is bigger at higher strain rate than at lower strain rate. The apparent activation energy (Q) and the apparent stress exponent (n) of the test steel are obtained to be about 462 kj/mol and 3.95, respectively. The relationship between peak stress (σp) and Zener-Holomon parameter (Z) is obtained, whereby the σp can be predicted at differern hot working conditons. The results of microstructural observation show that the austenite softens by the dynamic recrystallization (DRX) which can be dominantly responsib le for dynamic softening, while the ferrite phase mainly continues to exhibit dynamic recovery (DRV).
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Authors: Liang Li, Wen Kai Xiao, Tao Tao Fan, Zhou Quan Zhang
Abstract: By using the Gleeble - 1500 hot simulation test machine we studied 20#, 60Si2Mn, 9Cr18MoV the three kinds of low, medium and high carbon steels to observe the dynamic recovery and recrystallization of ferrite while in the process of thermoplastic deformation. We calculated the hot deformation activation energy of each kind of steel by combining the stress-strain curve we got in the experiment and the theoretical model of Z parameter. It turns out Q9Cr18MoV<Q20#<Q60Si2Mn. In the meanwhile, microstructure observation through transmission electron microscope shows that the dynamic recrystallization of ferrite is more likely to happen in 9Cr18MoV steel than in 20# steel and in 60Si2Mn steel. These results indicate that the dynamic recrystallization of ferrite is not only determined by stacking fault energy but also closely related with the strain storage energy release degree.
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Authors: Ali Gholinia, Ian Brough, John F. Humphreys, Pete S. Bate
Abstract: A combination of electron backscatter diffraction (EBSD) and focused ion beam (FIB) techniques were used to obtain 3D EBSD data in an investigation of dynamic recrystallization in a Cu-2%Sn bronze alloy. The results of this investigation show the origin of the nucleation sites for dynamic recrystallization and also elucidates the orientation relationship of the recrystallized grains to the deformed, prior grains and between the dynamically recrystallized grains.
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Authors: Matthew R. Barnett, Aiden G. Beer
Abstract: An analytical approximation for the steady state dynamic recrystallized grain size is combined with a simple nucleation criterion to assess the propensity for dynamic recrystallization. In line with observation, the criterion predicts dynamic recrystallization in 99.9995% pure Al but not in material 99.5% pure. It also agrees with the observation that zone refined ferrite can display dynamic recrystallization at high temperatures and low strain rates but not at lower hot working temperatures. The criterion is applied here to common wrought magnesium alloys to argue that conventional dynamic recrystallization is expected under "normal" hot working conditions.
369
Authors: Long Ping Shen, Zhao Yang Jin, Juan Liu
Abstract: According to the different softening mechanism, a flow stress model for magnesium alloy AZ31B is established. At the stage of dynamic recovery (DRV), the effect of work hardening (WH) and DRV on flow stress is described by dislocation evolution model. At the stage of dynamic recrystallization (DRX), the flow stress curve is obtained from Avrami equation denoting the recryatallization kinetics. Model parameter and its dependence on deformation condition are identified by the measured flow stress curve. The calculated curves agree well with the measured ones, which demonstrate the availability of the method.
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Authors: Ying Tong
Abstract: The cardan belong to dial the fork kind parts, its forming is difficult and forming high quality requirements. Establish macro-micro coupling, and a simulation model for the cardan negative extrusion forming process, a numerical simulation considering the deformation and heat conduction, deformation heat production, friction heat production, dynamic recrystallization and so on many factors. Analyze the deformation process detection cardan anti extruded deformation in advance and is extruded deformation. Meanwhile analysis showed that the cardan forgings have internal 59.929% area completely modification, have 4.7944% area did not happen dynamic recrystallization and didn't get forging modification, and forecasts the cardan internal grain size and distribution, the micro analysis for the prediction of forgings performance and design heat treatment process, provides the basis.
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Authors: Gilles Damamme, David Piot, Frank Montheillet, S. Lee Semiatin
Abstract: A simple mesoscale model was developed for discontinuous dynamic recrystallization. The material is described on a grain scale as a set of (variable) spherical grains. Each grain is characterized by two internal variables: its diameter and dislocation density (assumed homogeneous within the grain). Each grain is then considered in turn as an inclusion, embedded in a homogeneous equivalent matrix, the properties of which are obtained by averaging over all the grains. The model includes: (i) a grain boundary migration equation driving the evolution of grain size via the mobility of grain boundaries, which is coupled with (ii) a dislocation-density evolution equation, such as the Yoshie–Laasraoui–Jonas or Kocks–Mecking relationship, involving strain hardening and dynamic recovery, and (iii) an equation governing the total number of grains in the system due to the nucleation of new grains. The model can be used to predict transient and steady-state flow stresses, recrystallized fractions, and grain-size distributions. A method to fit the model coefficients is also described. The application of the model to pure Ni is presented.
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