Static Recrystallization Behavior Research Articles

Hot Deformation and Recrystallization Mechanisms in a Coarse-Grained, Niobium Stabilized Austenitic Stainless Steel (316Nb)

The hot deformation behavior and associated microstructural evolution of a coarse-grained Nb-bearing austenitic stainless steel (316Nb) has been investigated by the means of torsion tests at high temperature [1223 K to 1423 K (950 C to 1150 C)] followed by microstructural characterization. The starting microstructure was varied by applying prior annealing. Except for strains below 10 pct, the resistance to viscoplastic flow is not sensitive to the starting microstructure. On the other hand, prior annealing at higher temperatures increases the resistance to incipient viscoplastic flow and strongly impedes dynamic and post-dynamic recrystallization by delaying the grain boundary bulging phenomenon. It also affects the static recrystallization behavior during further annealing. The influence of the amount of available niobium atoms, in particular close to grain boundaries, is discussed.

Effects of Excess C on New Grain Formation and Static Recrystallization Behavior at Shear Bands in Cold-Rolled Ultra-Low Carbon Steel Sheets

Effects of Excess C on New Grain Formation and Static Recrystallization Behavior at Shear Bands in Cold-Rolled Ultra-Low Carbon Steel Sheets

Effect of electropulsing treatment on static recrystallization behavior of cold-rolled magnesium alloy ZK60 with different reductions

Effect of electropulsing treatment (EPT) on recrystallization behavior of cold-rolled Mg alloy ZK60 strips was investigated. It was found that EPT significantly improved nucleation rate and migration ability of grain boundaries, leading to accelerated recrystallization of the deformed metals at relatively low temperature. After the recrystallization induced by EPT, the average grain size of 20% rolling reduction samples decreased from 113 μm to around 10 μm, meanwhile the typical basal-type texture of the cold-rolled sample was weakened. EPT was normally accompanied with a thermal and an athermal effects. The athermal effect played a dominated role in increasing nucleation rate, while the thermal effect promoted grain growth. A fewer recrystallized grains originated along the grain boundaries in the 10% reduction samples, while most of the recrystallization took place inside the twins in the 20% reduction samples.

Thermo-mechanical processing window for β phase recrystallization inTi-5Al-5Mo-5V-3Cr alloy

Ti-5Al-5Mo-5V-3Cr (Ti-5553) is a high strength β titanium alloy. It is now commonly used in thick section aerospace components. In general, the thermo-mechanical processing (TMP) of β titanium alloys done at high temperature to obtain uniformly recrystallized fine grain structure is one of the major challenges. Through this work, a TMP window for Ti-5553 (through systematic variation in % reduction and post deformation annealing temperature) has been developed to obtain fine uniformly recrystallized β grains. Grain size has been quantified on EBSD generated orientation maps, by applying stereological methods, image processing and automated reconstruction. Effects of % deformation and post deformation annealing temperature, as well as that of initial ingot size prior to deformation and the capacity of the forge on the static and dynamic recrystallization behavior, which eventually determine the final grain size distribution, have been illustrated.

WITHDRAWN: Static recrystallization behavior of multi-directional impact forged Mg-Gd-Y-Zr Alloy

WITHDRAWN: Static recrystallization behavior of multi-directional impact forged Mg-Gd-Y-Zr Alloy

The Recrystallization Behavior of Unalloyed Mg and a Mg-Al Alloy

The static recrystallization behavior of pure Mg and Mg-4Al was characterized over a range of annealing temperatures. The electron backscatter diffraction grain orientation spread technique was used to quantify the level of recrystallization at various annealing times. Recrystallization kinetics were characterized using the Johnson–Mehl–Avrami–Kolmogorov (JMAK) relationship and it was found that two sequential annealing stages exist. Stage 1 involves heterogeneous nucleation of recrystallization in regions with a high stored energy, including twins and grain boundaries, and can be represented by an Avrami exponent of n1 ranging from 0.35 to 0.6. During Stage 2, recrystallization occurred predominately in the interior of deformed grains with incomplete recrystallization generally observed even at annealing times in excess of two weeks. The second recrystallization stage exhibited a much lower Avrami exponent, n2, ranging from 0.02 to 0.2. Increasing the starting grain size in the pure Mg condition led to a significant delay in recrystallization. The addition of Al had a minimal effect on the recrystallization kinetics of Mg.

A modified Avrami equation for kinetics of static recrystallization of Nb-V microalloyed steel: Experiments and numerical simulation

Static recrystallization behavior of Nb-V microalloyed steel was investigated by experiments and numerical simulation method. A series of two-stage hot compression tests were performed on Gleeble 1500. Based on the tested flow stress curves, the conventional kinetics model of SRX was established. It is found that there exists a large deviation between experimental SRX fraction and predicted ones. Then, according to the analysis of SRX characteristics of the tested steel, a modified Avrami model was proposed. The comparison result shows that the modified model can accurately describe the SRX fraction. In addition, the SRX behavior of the tested steel was simulated by finite element method (FEM). The effects of deformation parameters on SRX fraction were analyzed. And the simulation SRX fractions are verified by the experimental and calculated ones.

A Comparative Study on the Static Recrystallization Behavior of Cold-Rolled Mg-3Al-1Zn Alloy Stimulated by Electropulse Treatment and Conventional Heat Treatment

Cold-rolled AZ31 Mg alloy strips, with a reduction of 33 pct, were subjected to electropulse treatment (EPT) and conventional heat treatment (HT) to evaluate the respective influences of electropulses and temperature on the recrystallization behavior of AZ31. The highest measured temperature during the EPT (543 K) was used in HT. The electron backscattered diffraction results demonstrated that the EPT-stimulated recrystallization was completed within 8 seconds, whereas for HT, recrystallization was still far from completion even after 240 seconds. It was found that both the nucleation and grain growth of these two processes were totally different. In the EPT samples, nucleation tended to occur preferentially near extension twin boundaries and grain boundaries by continuous recrystallization, whereas in the HT samples, nucleation occurred mainly by grain boundaries bulging via discontinuous recrystallization. As grain growth proceeded, the texture intensities of the EPT samples decreased gradually and finally evolved into an obvious transverse-direction-split texture. This is likely attributable to the impact of electropulses on the boundary energy and the contribution of nonbasal dislocations; however, the basal-type textures of the HT samples were notably strengthened, which is associated with a 30 deg〈0001〉 orientation with respect to the deformed texture.

Study on Static Recrystallization Behavior of Medium-Carbon Cr-Ni-Mo Alloyed Steel During Hot Deformation

A series of two-pass hot compression tests were conducted on Gleeble-1500 thermo-mechanical simulator to investigate the static recrystallization (SRX) behavior of a medium-carbon Cr-Ni-Mo alloyed steel 34CrNiMo. The compression tests were performed at a deformation temperature range of 950-1150 °C, a strain rate range of 0.1-3.5 s−1, and an interval time range of 1-100 s. The experimental flow stress curves and microstructural observation indicate that deformation temperature, pass interval time, strain rate, and pre-strain have significant influences on the recrystallization behavior of 34CrNiMo steel. It is identified that the softening fraction increases with the increasing deformation temperature, pre-strain, and interval time, while it decreases with the increasing strain rate. Based on the experimental data, the SRX kinetics equations of 34CrNiMo steel were developed. And the calculated results are in good agreement with the experimental ones, which demonstrates that the established equations can be used to describe the SRX behavior of 34CrNiMo steel at elevated temperatures.

Static Recrystallization Behavior of Z12CN13 Martensite Stainless Steel

In order to increase the hot workability and provide proper hot forming parameters of forging Z12CN13 martensite stainless steel for the simulation and production, the static recrystallization behavior has been studied by double-pass hot compression tests. The effects of deformation temperature, strain rate and inter-pass time on the static recrystallization fraction by the 2% offset method are extensively studied. The results indicate that increasing the inter-pass time and the deformation temperature as well as strain rate appropriately can increase the fraction of static recrystallization. At the temperature of 1050-1150 °C, inter-pass time of 30-100 s and strain rate of 0.1-5 s−1, the static recrystallization behavior is obvious. In addition, the kinetics of static recrystallization behavior of Z12CN13 steel has been established and the activation energy of static recrystallization is 173.030 kJ/mol. The substructure and precipitates have been studied by TEM. The results reveal that the nucleation mode is bulging at grain boundary. Undissolved precipitates such as MoNi3 and Fe3C have a retarding effect on the recrystallization kinetics. The effect is weaker than the accelerating effect of deformation temperature.

Static recrystallization behavior of hot-rolled Mg-Zn-Ce magnesium alloy sheet

Static recrystallization behavior of Mg-1.5Zn-0.2Ce (wt%) alloy rolled at 480 °C was investigated at different annealing stages using quasi-in-situ electron backscattered diffraction (EBSD) analyses, which were carried out repeatedly in the same region to trace microstructural evolution. In the as-rolled condition, double twins exhibit the highest fraction compared with tensile and compression twins. Double twins mostly exist in deformed grains with basal orientations, and statically recrystallized grains mainly nucleate at the intersections of double twins and pre-existing grain boundaries. Statically recrystallized grains tend to exhibit TD-tilted orientations and grow along double twins to consume adjacent basal-oriented grains. This is the main reason for inducing the change from a RD-split texture to a well-weakened TD-split texture during annealing. The residual unrecrystallized grains with TD-tilted orientations and the growth advantage of TD-tilted grains also enhance the formation of TD-split texture.

Static recrystallization behaviour of cold rolled Mg-Zn-Y alloy and role of solute segregation in microstructure evolution

We examined the microstructure and texture evolution during the recrystallization annealing of cold rolled Mg-1Y and Mg-0.2Zn-1Y alloys. At the early annealing stage, new grains are nucleated on sub-units with 200–300nm surrounded by dislocation walls within shear bands. The Zn and Y addition reduced the stacking fault energy which results in the high activity of non-basal deformation mechanisms and formation of segregation zones along the stacking faults. This causes the orientation of recrystallization nuclei to be effectively retained so that the texture weakens during the recrystallization without reducing the basal pole split into the sheet transverse direction.

Static recrystallization behavior of 25CrMo4 mirror plate steel during two-pass hot deformation

The static recrystallization behavior of 25CrMo4 mirror plate steel has been determined by hot compression testing on a Gleeble 1500 thermal mechanical simulation tester. Compression tests were performed using double hit schedules at temperatures of 950–1150 °C, strain rates of 0. 01–0. 5 s−1, and recrystallization time of 1–100 s. Results show that the kinetics of static recrystallization and the microstructural evolution were greatly influenced by the deformation parameters (deformation temperature, strain rate and prestrain) and the initial austenite grain size. Based on the experimental results, the kinetics model of static recrystallization has been generated and the comparison between the experimental results and the predicted results has been carried out. It is shown that the predicted results were in good agreement with the experimental results.

Study of factors affecting simulation of static recrystallization of Ni-based superalloy through cellular automaton model

The static recrystallization (SRX) behavior of Ni-based superalloy was investigated through cellular automaton (CA) model. The hot compress tests were carried out under the strain rates (s-1) of 0.01, 0.1 and temperature of 1313K. The associated parameters of simulations could be calculated through the data of curves obtained from above experiments and other material parameters. The simulations provide insight into the factors affecting the SRX microstructure evolution significantly involving the time step, size of cell, nucleation locationand orientation of nucleation. Then the comparisons between experimental and predicted microstructuresand the contrast between simulated and physical averaged grain size are presented and analyzed. As a result, the accurate simulation result is sensitive to these factors mentioned above.

Static and Metadynamic Recrystallization Behaviors of Heat-resistant P91 Alloy during Hot Deformation

Static and Metadynamic Recrystallization Behaviors of Heat-resistant P91 Alloy during Hot Deformation

Static recrystallization behaviour of Ti-Nb microalloyed high-strength steel

Static recrystallization behaviour of Ti-Nb microalloyed high-strength steel

Effect of Carbon Content on Static Recrystallization Behavior of Work-Hardened Austenite in Low Alloy Steel and Its Mechanism

Effect of Carbon Content on Static Recrystallization Behavior of Work-Hardened Austenite in Low Alloy Steel and Its Mechanism

Effects of Alloying Elements on Static Recrystallization Behavior of Work-Hardened Austenite of High Carbon Low Alloy Steel

Effects of Alloying Elements on Static Recrystallization Behavior of Work-Hardened Austenite of High Carbon Low Alloy Steel

Analysis of the Static Recrystallization Behavior of Nb-Ti Microalloyed Steels Including Low Strain Levels

Semi-empirical models for predicting the austenite static recrystallization behavior are widely used in designing thermomechanical treatments to improve final mechanical properties. However, a problem with these models is that their utility can be limited to the range of deformation conditions and chemical compositions they were developed for. This work focuses on the study of the applicability of current recrystallization models to the range of low strain conditions and/or high Nb microalloying additions (≈0.1%). To do so, the recrystallization behavior of two low carbon Nb-Ti microalloyed steels (0.04 and 0.11% Nb and ≈0.01% Ti) has been investigated by torsion tests. Experimental results for recrystallization time and recrystallized grain size have been compared to previously developed equations. It has been observed that at low strains (ε = 0.1) the predictions fail. A dependence of the n Avrami exponent both on temperature and applied strain was also found.

Static Recrystallization Behavior of SA508-III Steel during Hot Deformation

The static recrystallization behavior of SA508-III steel was investigated by isothermal double-hit hot compression tests at the deformation temperature of 950–1250 °C, the strain rate of 0. 01–1 s−1, and the inter-pass time of 1–300 s. The effects of deformation parameters, including forming temperature, strain rate, degree of deformation (pre-strain) and initial austenite grain size, on the softening kinetics were analyzed. Experimental results show that static recrystallization kinetics is strongly dependent on deformation temperature and degree of deformation, while less affected by the strain rate and initial grain size. The kinetics and microstructural evolution equations of static recrystallization for SA508-III steel were developed to predict the softening behavior and the statically recrystallized grain size, respectively. Based on the comparison between the experimental and predicted results, it is found that the established equations can give a reasonable estimate of the static softening behavior for SA508-III steel.