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The Epoxy-based hybrid composites are attention in various engineering domains. Distinctively, natural fiber-made epoxy composites are advantageous over synthetic fiber-made composites and attracted in automotive applications such as set frames, interior panels, dashboards, etc. Moreover, due to its high moisture absorption nature, the epoxy composite formed with natural fiber is suspected to have poor adhesive quality compared to synthetic fiber composite. It leads to lower adhesive performance and limits the behaviour of composite. The prime objective of the current work is to ensure the adhesive behaviour of NaOH-treated sisal fiber (SF) epoxy composite featured with silicon carbide nanoparticles (SiC). This composite is prepared with the constant percentage of SF as 15 wt% and varied wt% of SiC through compression mould technology. Influences of treated SF and SiC on pressing behaviour of surface morphology, tensile & flexural strength, microhardness, and fracture toughness of composites are experimentally investigated with ASTM D638, D790, D4762, and D6110 policy, and its outcomes are compared to 15wt% treated SF epoxy composite. The surface morphology study confirms that the SF and SiC appearances in the epoxy matrix are uniform and homogenous. The 5wt% SiC embedded with 15wt% treated SF facilitates higher tensile (65.2 ± 1.1 MPa) & flexural strength (69.1 ± 1.3 MPa), microhardness (35.5 ± 0.5 HV), and fracture toughness (1.56 ± 0.01 MPam0.5). The enriched epoxy hybrid composite sample will recommended for automobile interior parts application. [ABSTRACT FROM AUTHOR]

Hybrid polymer composites are composed of fiber and filler reinforcements found to have superior specific characteristics, and it is better than monolithic polymers. The motto of the research is to enrich the properties of epoxy composite by incorporating a multi-fiber/filler combination synthesized via an advanced hot compression technique. The synthesized composites contained epoxy combinations of sisal fiber (SF), glass fiber (GF), sisal-glass fiber (SGF), and SGF with silicon carbide (SiC) are involved in X-ray diffraction (XRD) analysis, tensile/flexural strength, microhardness, and fracture toughness performance evaluation. The advanced hot compression technique has proved that better dispersion of fiber and filler in epoxy resin results in better mechanical properties. The significance of multi-fiber/filler combination (SGF-SiC) in epoxy facilitates maximum tensile, flexural, and microhardness performance and better fracture toughness behaviour of 388 ± 12 MPa, 291 ± 8 MPa, 138 ± 5 HV, and 4.7 ± 0.1 J/cm2. The enriched epoxy hybrid composite composed of SGF-SiC will be suggested for auto-aerospace cabinet applications. [ABSTRACT FROM AUTHOR]

The evolution of microstructure during hot deformation is key to achieving good mechanical properties in aluminum alloys. We have developed a cellular automaton (CA) based model to simulate the microstructural evolution in 7075 aluminum alloy during hot deformation. Isothermal compression tests were conducted to obtain material parameters for 7075 aluminum alloy, leading to the establishment of models for dislocation density, nucleation of recrystallized grains, and grain growth. Integrating these aspects with grain topological deformation, our CA model effectively predicts flow stress, dynamic recrystallization (DRX) volume fraction, and average grain size under diverse deformation conditions. A systematic comparison was made between electron back scattered diffraction (EBSD) maps and CA model simulated under different deformation temperatures (573 to 723 K), strain rates (0.001 to 1 s−1), and strain amounts (30% to 70%). These analyses indicate that large strain, high temperature, and low strain rate facilitate dynamic recrystallization and grain refinement. The results from the CA model show good accuracy and predictive capability, with experimental error within 10%. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Central South University is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study researched how Ce addition affects the microstructure and mechanical behavior of Cu-Fe-Ti-Mg alloys during hot compression. A thermal deformation simulation machine was used to study the hot compression process at 0.001-10 s−1 strain rates and 500-950 °C deformation temperatures. The true stress–strain curves and constitutive equations were obtained for the two alloys. Based on the electron backscatter diffraction analysis, the addition of Ce can improve the dislocation density and texture strength of the Cu-Fe-Ti-Mg alloy. The microstructure and precipitates of the Cu-Fe-Ti-Mg-Ce alloy were also analyzed. The average grain size of the Cu-Fe-Ti-Mg-Ce alloy is smaller than the Cu-Fe-Ti-Mg alloy. The addition of Ce delayed dynamic recrystallization. These findings provide a theoretical foundation for understanding the Ce addition effects on the hot deformation behavior of the Cu-Fe-Ti-Mg alloy, serving as a reference for industrial manufacturing of the alloy. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Central South University is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The flow curves of Al-7.8Zn-1.65Mg-2.0Cu (wt.%) alloy in the temperature range of 300-450 °C and strain rate range of 0.01-10 s−1 were obtained by hot compression tests on a Gleeble-3500 isothermal simulator. The effects of deformation heat-induced temperature rising and friction on the flow curves were discussed and the flow curves were corrected to exclude these influences. The constitutive model was constructed and its accuracy was evaluated by the correlation coefficient (R) and average absolute relative error. The values of the corresponding evaluators were determined to be 0.9841 and 6.2346%, respectively. The processing maps were developed and through which the optimal hot working window for this alloy was determined in the range of 380-450 °C and 0.01-0.368 s−1. The microstructure evolution observations revealed that micro-crack and flow localization occurred at 300 °C and 10 s−1 and 400 °C and 10 s−1, which located in the instability region of processing map. With the increasing strain rate, the deformation activation energy decreased, simultaneously, the dislocation multiplication rate accelerated, which resulted in pronounced increasing of LAGBs and HAGBs. [ABSTRACT FROM AUTHOR]

In this study, the effect of adding 3 wt.% of light (Ce) and heavy (Y) rare earth elements on the microstructure and hot compression behavior of Mg-6 wt.% Zn-0.5 wt.% Zr (ZK60) extruded alloy was investigated. A compression test was performed on extruded alloys in the range of 0.001–1 s−1 strain rate and 250-400 °C temperature. By adding rare earth elements to the alloy, in addition to the Mg7Zn3 precipitates in ZK60 alloy, MgZn2Ce precipitates and Mg24Y5 and Mg3Y2Zn3 precipitates are formed in ZK60-3Ce and ZK60-3Y alloys, respectively. In addition to increasing the volume fraction of precipitates, rare earth elements also cause grain refinement. Hot working behavior was investigated using the modified hyperbolic sinus method. Stress exponent values between 5 and 7 and activation energy between 125 and 150 kJ mol−1 were obtained. Lattice self-diffusion for ZK60 alloys and cross-slip in alloys containing rare earth elements were suggested as deformation mechanisms. With the help of processing maps, suitable temperature and strain rate for hot working were obtained. It was found that with the addition of rare earth elements, the stable area becomes wide and the unstable areas become narrow. [ABSTRACT FROM AUTHOR]

In the present study, the hot compressive deformation behavior of Ti-Nb bearing microalloyed steel was investigated in the temperature range of 850–1100 °C and strain rates of 0.01–1 s−1. Flow curves obtained from hot compression tests were analyzed, and it was demonstrated that dynamic recrystallization is the main softening mechanism during deformation at 900, 1000, and 1100 °C at all strain rates. It was also demonstrated that dynamic recovery occurs during deformation at 800 °C. Based on the obtained results, an artificial neural network was constructed to predict the hot flow softening behavior of Ti-Nb microalloyed steel which is due to the occurrence of dynamic recrystallization and recovery. Results obtained from artificial neural network were compared with the experimental values of flow stress, and a very good correlation was observed between them. This indicates the excellent capability of the developed artificial neural network to predict the flow softening due to complex microstructural evolutions accompanying dynamic recrystallization and dynamic recovery. [ABSTRACT FROM AUTHOR]

To study the effects of dynamic precipitation and processing parameters on the dynamic recrystallization (DRX) behavior of 2195 Al-Cu-Li alloy, the hot deformation process was investigated comprehensively with the temperature range of 300-500°C and strain rate range of 0.001-10 s-1. An Arrhenius-type constitutive equation and DRX kinetics model were established based on the corrected stress-strain data to unveil the relationship between processing parameters, flow stress and DRX behavior. The shape of flow curves was associated with the dynamic softening mechanism and the DRX softening fraction gradually increased with the decrease of Zener-Hollomon parameter (Z). Then, the microstructure evolution was further analyzed to elucidate the DRX mechanisms at various Z values. The primary softening mechanism was dynamic recovery (DRV). However, when temperature set between 300 and 400°C, T1 and cubic phases significantly impeded DRV and promoted the occurrence of discontinuous dynamically recrystallization (DDRX) by a strong pinning effect and considerable driving force. As Z value decreased, the recrystallization mechanism transformed from DDRX into continuous dynamic recrystallization (CDRX) attributed to the higher mobility for dislocations. Due to the reduced stored energy and the hindrance of precipitates, grain boundaries were hard to migrate, making it difficult for DDRX grains to grow continuously. [ABSTRACT FROM AUTHOR]

The flow stress curves of a Nb–Ti microalloyed C–Mn–Al high strength steel were obtained by hot compression experiment with Gleeble-1500 thermal simulator at the temperatures from 900 to 1100 °C and strain rates from 0.01 to 30 s−1. Firstly, strain-compensated physical constitutive models considering the temperature dependence of Young's modulus (E) and austenite self-diffusion coefficient (D) with creep stress exponent 5 and variable stress exponent n ′ were established, respectively. Secondly, the traditional apparent Arrhenius constitutive model was established to compare the accuracy of the models. The results show that the physical constitutive model with exponent n ′ has higher accuracy to predict the flow stress of the experimental steel (correlation coefficient R = 0.992, average absolute relative error δ = 3.83%) than the model with exponent 5 (correlation coefficient R = 0.990, average absolute relative error δ = 10.54%). This is because when the stress exponent in the physical constitutive model is 5, it means that the deformation mechanism considered is only slip and climb, and the constitutive model with variable stress exponent n ′ considers all the deformation mechanisms comprehensively, so the prediction accuracy is higher. The correlation coefficient R of the Arrhenius constitutive model is 0.991, and the average absolute relative error δ is 4.58%. Therefore, the physical constitutive model with exponent n ′ has the highest prediction accuracy in this study, thus can be an alternative way to predict the flow curves of steels. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the effects of temperature and strain rate on the hot deformation behavior of a medium-carbon structural steel. This steel is known as 30XΓCA steel in GOST standard and contains 0.3 wt % carbon. To investigate the hot deformation behavior of this steel, hot compression tests were performed on cylindrical samples in temperature ranges from 800 to 1000°C and strain ranges from 0.001 to 0.1 s–1. Microstructure of samples was characterized using optical microscopy (OM) and scanning electron microscopy (SEM). The true stress-strain curves of 30XΓCA steel obtained at various deformation conditions showed that the softening phenomenon based on recovery and dynamic recrystallization (DRX) occurred during hot deformation tests. The results indicated that the peak stress decreased with increasing temperature and decreasing strain rate. With increasing temperature from 800 to 1000°C, the peak stress decreased by 52, 60, and 38% at strain rates of 0.001, 0.01 and 0.1 s–1, respectively. According to the results, it can be claimed that the DRX was a dominate mechanism of softening in all deformation conditions. The changes of work hardening rate for 30XΓCA steel during hot deformation were analyzed to confirm the results. Accordingly, it was observed that critical stress for the initiation of DRX decreased with increasing temperature and decreasing strain rate. Furthermore, constitutive equations and activation energy of deformation for 30XΓCA steel were successfully determined. Based on the hyperbolic sine equation, the activation energy of hot deformation of 30XΓCA steel was 256.11 kJ/mol. [ABSTRACT FROM AUTHOR]

Hot compression tests were performed on AISI 321 austenitic stainless steel in the deformation temperature range of 800–1200°C and constant strain rates of 0.001, 0.01, 0.1, and 1 s−1. Hot flow curves were used to determine the strain hardening exponent and the strain rate sensitivity exponent, and to construct the processing maps. Variations of the strain hardening exponent with strain were used to predict the microstructural evolutions during the hot deformation. Four variations were distinguished reflecting the different microstructural changes. Based on the analysis of the strain hardening exponent versus strain curves, the microstructural evolutions were dynamic recovery, single and multiple peak dynamic recrystallization, and interactions between dynamic recrystallization and precipitation. The strain rate sensitivity variations at an applied strain of 0.8 and strain rate of 0.1 s−1 were compared with the microstructural evolutions. The results demonstrate the existence of a reliable correlation between the strain rate sensitivity values and evolved microstructures. Additionally, the power dissipation map at the applied strain of 0.8 was compared with the resultant microstructures at predetermined deformation conditions. The microstructural evolutions strongly correlated to the power dissipation ratio, and dynamic recrystallization occurred completely at lower power dissipation ratios. [ABSTRACT FROM AUTHOR]

Hot forged 1Cr–1Mo and 9Cr–1Mo steels are being progressively used in the making of the turbine rotors of steam power plants. Forging of these steels requires precise control of processing parameters (i.e. strain, strain rate and temperature) for a defect free product. In line with the above mentioned applications, a comparative study to analyze the hot deformation behavior of both the steels was carried out in the temperature domain of 850–1050 °C with varying strain rate (0.001–0.1 s−1) by compression test data obtained from Gleeble 3800® thermomechanical simulator up to true strain of 0.69. The flow stress behavior of hot compressed specimens was analyzed by using material constants, activation energy and formulated Zener–Hollomon parameter. Critical conditions for dynamic recrystallization (DRX) of both the steels were calculated with the help of a mathematical model developed by Poliak and Jonas. Further, the variations in critical conditions were correlated with the Zener–Hollomon parameter. For both the steels, the current study also focused on the comparison of dynamically recrystallized austenite ( X DRX ) volume fraction with respect to true strain by applying the concept of Avrami equation. Finally, to validate the kinetics of DRX and softening mechanism, the microstructural evaluation and characterization have been carried out using optical and electron microscopy. [ABSTRACT FROM AUTHOR]

In this study, microstructure and texture evolution of TB8 titanium alloys during hot deformation were investigated by using electron back-scattered diffraction (EBSD) analysis. The results showed that dynamic recrystallization (DRX) behavior of TB8 titanium alloys was drastically sensitive to the strain. As the true strain raised from 0.2 to 0.8, the degree of DRX gradually increased. The nucleation mechanism of recrystallization was observed, including discontinuous dynamic recrystallization (DDRX) resulting from the bulging of original boundaries. Furthermore, continuous dynamic recrystallization (CDRX) occurred because of the transformation of low-angle grain boundaries (LAGBs) to high-angle grain boundaries (HAGBs) in the interior of the original deformed grains. The texture evolution of TB8 titanium alloy during hot deformation process was analyzed in detail, and five texture components were observed, including {001} 100 , {011} 100 , {112} 110 , {111} 110 , and {111} 112 . As the true strain increased, deformation textures were gradually weakened due to an increase in the volume fraction of DRX grains. When the true strain was 0.8, the main texture components consisted of the recrystallization texture components of the {001} 100 and {011} 100 textures. [ABSTRACT FROM AUTHOR]

Dynamic recrystallization (DRX) behavior of two binary Mg–0.5Gd and Mg–1.5Gd alloys and pure Mg were studied by hot compression in the temperature range of 300–450 °C to explore the role of Gd on DRX grain size refinement and kinetics. The dependency of DRX grain size on the Gd content during hot compression was quantified and expressed based on the Zener–Hollomon parameter. While the exponent of the Zener–Hollomon parameter was obtained as − 0.118 independent of the Gd content, the proportionality constant varied by Gd concentration. The developed expression revealed significant reduction in the DRX grain size of the Mg–Gd alloys. The volume fraction of dynamically recrystallized grains was calculated by applying the Johnson–Mehl–Avrami–Kolmogorov type model, which resolved the faster kinetics for DRX of the Mg–1.5Gd alloy compared to ones for the Mg–0.5Gd alloy and pure Mg. The higher driving pressure for DRX of the Mg–1.5Gd alloy was justified based on dislocation density measurements at the onset of DRX through the Williamson-Hall method. The role of Gd on dynamic recrystallization behavior of Mg during hot compression was studied. A linear relationship between the DRX grain size and Gd content was developed and dislocation density of the binary Mg-Gd alloys and pure Mg at the onset of DRX during hot compression was measured. [ABSTRACT FROM AUTHOR]

The optimal process parameters of grade 250 maraging steel for hot forging were investigated with a process map and microstructure analysis. To generate the process map, hot compression tests were performed at 800–1200 °C and strain rates of 0.01–5 s−1. The flow stress–strain curves were calibrated by Bayesian artificial neural network (ANN) modeling to compensate the heat generated by dynamic deformation. The Ni and Mo segregation during the solidification of the ingot caused alternating layers of Ni- and Mo-rich and -lean bands, which affected the recrystallization behavior during hot compression. According to the calculated process map, 1100–1200 °C × 0.01–0.7 s−1 and 1000–1200 °C × 0.01–0.2 s−1 are favorable process conditions that ensure wide process windows in terms of strain rate and temperature, respectively. The common features of the microstructure deformed under both conditions were relatively coarse martensite blocks and low values in the electron backscattered diffraction (EBSD) kernel average misorientation (KAM) results (i.e., low residual stresses), which were attributed to a low fraction of fine martensite block region. [ABSTRACT FROM AUTHOR]

An Al–Cu–Mg–Zr alloy, which obtained different homogenization cooling rates by changing the heat-treated sample size, was compressed to various strains at the deformation temperature of 300 ºC and strain rate of 0.01 s−1. The results showed that the homogenization cooling rate had strong effects on the hot deformation behavior of the alloy. The flow stress and relative dynamic softening rate of the alloy were significantly higher under a high cooling rate (HCR) than those under a low cooling rate (LCR). Furthermore, based on X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and thermodynamic equilibrium phase calculation, the substructure evolution in the grain interior, morphology, and spatial distribution of the precipitates were studied to determine the differences in the flow softening mechanism. The main softening mechanism could be summarized as dynamic recovery and precipitation coarsening for the LCR alloy and dynamic precipitation for the HCR alloy. [ABSTRACT FROM AUTHOR]

By means of isothermal compression at temperatures in the range of 650–900 °C and strain rates in the range of 0.001–1 s−1, the dynamic recrystallization behavior and microstructural evolution of a Cu–3.28Ni–0.6Si–0.22Zn–0.11Cr–0.04P (wt%) alloy designed by a machine learning method were investigated. A semiempirical constitutive equation, processing maps and an average activation energy were generated. The microstructure under different conditions and the effect of strain rate on the texture of the alloy at 800–900 °C were observed. The results show that the suitable temperature is 800–900 °C; when the strain is less than 0.4, the appropriate strain rate is 0.01–0.5 s−1; and when the strain is greater than 0.4, the appropriate strain rate is below 0.05 s−1. After deformation at 800 °C, the main texture changed from {112}〈111〉 of copper to a uniform distribution with the increase in strain rate, but the sample did not have obvious texture after deformation at 850 and 900 °C. The above results can provide a reference for the selection of process parameters. [ABSTRACT FROM AUTHOR]

For simulating the hot deformation behavior of a powder metallurgy nickel-base superalloy during isothermal forging, the hot compression tests were performed in the temperatures of 1020-1110 °C with the strain rates from 10−3 to 1 s−1. The thermoplastic deformation and dynamic recrystallization (DRX) behavior of the superalloy during thermocompression were systematically studied. It can be shown that the flow stress of the superalloy exhibits apparent characteristics of DRX. A relationship indicating the dependency of flow stress on deforming temperature and strain rates is built through introducing the Z parameter. The work-hardening rate (θ) curves of the superalloy at various deformation conditions are obtained, and the values of θ are found to decrease with decreasing Z parameter, i.e., decreasing strain rates and increasing deforming temperature. There exists a power exponential relationship between critical strain εc and Z parameter. Combining the experimental data, a two-stage constitutive model on the basis of the Estrin–Mecking constitutive model and the DRX kinetic model is set up to model the flow stress of the superalloy. The flow stresses obtained from the established model are well consistence with the measured values. [ABSTRACT FROM AUTHOR]

In this study, the effect of boron addition on the hot compression behavior and dynamic recrystallization kinetics of 718Plus nickel-based superalloy were investigated by isothermal compression tests at the deformation temperature range of 900-1050 °C and strain rate range of 0.01-1 s−1. Optical and field emission scanning electron microscopy techniques were employed to investigate the microstructural evolutions. The results indicated that the addition of boron reduces the flow stress of 718Plus superalloy. This could be attributed to the decrease in the volume fraction of Ni3(Al, Ti) particles. Microstructural observations revealed more volume fraction of dynamic recrystallization in the boron-bearing alloy at low-deformation temperatures, i.e., 900 and 950 °C. In contrast, at high temperatures of 1000-1050 °C, recrystallization is retarded mainly due to the segregation of boron to the grain boundaries. [ABSTRACT FROM AUTHOR]

The dynamic recrystallization (DRX) behavior of INCONEL 690 (IN690) alloy was studied using electron backscatter diffraction (EBSD) and transmission electron microscopy. Isothermal compression tests were performed on a Gleeble-3500 simulator under temperatures 950-1100 °C, strain rates 0.01-1 s−1, and the maximum true strain 0.8. An Avrami-type model was developed to investigate the DRX behavior of IN690; it was found to be extremely sensitive to the processing parameters of temperature, strain rate, and true strain. As temperature increased and strain rate decreased, the activation energy increased, thus accelerating movement of dislocation and migration of grain boundaries, causing DRX behavior acceleration. The DRX behavior is accompanied by dislocation rearrangement and annihilation. The DRX mechanism of IN690 is dominated by discontinuous dynamic recrystallization (DDRX) and supplemented by continuous dynamic recrystallization (CDRX). A key characteristic of DDRX is grain-boundary bulges, while CDRX features progressive sub-grain rotation, leading to migration of low-angle grain boundaries to high-angle grain boundaries. A series of constitutive models were embedded into finite-element method software to study the DRX behavior of IN690. The results show that the microstructure evolution regularity obtained by the simulation method is consistent with the experimental values, which provides a basis for computer simulations of the hot machining process. [ABSTRACT FROM AUTHOR]

In the present work, isothermal hot pressing of a Mg-14Li-Al (wt%) alloy, considered as the lightest metallic alloy, is studied through microstructure, hot compression flow stress curve, and indentation load/displacement plots. The main objective is to correlate the microstructure with the small-scale properties and processing parameters (i.e., thermomechanical parameters like temperature and strain rate). The thermomechanical cycle consists of uniaxial compression tests at temperatures of 250 °C, 350 °C, and 450 °C and strain rates of 1, 0.1, 0.01, and 0.001/s using a Gleeble® 3500 thermal-mechanical simulation testing system. True stress-true strain curves plotted from the thermomechanical tests were used to assess the working behavior of the materials and to analyze and to understand the microstructure evolution which reflects intrinsic mechanical properties. Finally, a comparison has been done in between our previously published article Mg-3.5Li-Al (International Journal of Lightweight Materials and Manufacture 2 (2019) 217–226) and the current work on Mg-14Li-Al alloy in terms of the microstructural changes, hot compression stress-strain curves, and the nanoindentation load/displacement response. [ABSTRACT FROM AUTHOR]

The most prevalent hybrid additive manufacturing (HAM) method in the industry involves the combination of conventional processes, such as hot isostatic pressing or forging. In this way, a part is printed to its near-net-shape by additive manufacturing and then finished using open forge (Ampliforge). Hereby, the performance of the printed part will be improved by the downstream processes; this method also affords a reduction in time, cost, and waste material. In this study, the AISI 316L stainless steel parts were produced through selective laser melting (SLM) process and the cellular structure with columnar grains appeared. Then, hot compression experimental works were performed to investigate flow behavior, hot workability, density, and microstructure evolutions during the process. This process resulted in a near fully-dense part with a homogeneous microstructure without anisotropy of properties and higher hot deformation activation energy and peak stress in comparison with similar conventionally manufactured stainless steel. [ABSTRACT FROM AUTHOR]

The behavior of a VTI-4 (Ti–22Al–25Nb) alloy during hot compression at a strain rate of ~2.5 s–1 is studied. Hot compression to a strain of 65% is carried out in the temperature range 850–1020°C, covering two phase regions β + Ο and β + α2. Hot compression results in the dissolution and spheroidization of lamellar O and α2 phases in the severe deformation zone. X-ray diffraction analysis does not reveal any qualitative changes in the phase composition after deformation. Energy dispersive X-ray spectroscopy (EDS) analysis conducted on a transmission electron microscope indicates niobium depletion of the O phase when the hot compression temperature increases or during compression. Niobium-depleted zones form near interphase boundaries during the dissolution and spheroidization of lamellar-shaped O and α2 phases. The dissolution and spheroidization process includes two stages. The first stage involves defect accumulation in the O-phase and α2-phase lattices, and it is accompanied by a simultaneous increase in the temperature due to deformation-induced heating. The second stage icludes niobium redistribution between the β matrix and the phase in defective sites, which leads to phase dissolution and spheroidization. [ABSTRACT FROM AUTHOR]

To increase the hot workability and provide proper hot forming parameters of a 9Ni590B steel for the simulation and production, the hot deformation behavior of the 9Ni590B steel is investigated through isothermal compression tests using a Gleeble-3180 thermal–mechanical simulator over a temperature range of 850-1200 °C with strain rates of 0.001-5 s−1. The results indicate that as the deformation temperature increases and the strain rate decreases, the flow stress of the 9Ni590B steel decreases. The deformation–activation energy was calculated to be 364.99 kJ/mol based on the flow stress curve data. The dynamic material model (DMM) was used to establish the process map of the thermal deformation for the 9Ni590B steel. The results show that the optimal deformation conditions for the 9Ni590B steel hot working are with a temperature range of 1100-1200 °C and a strain rate range of 0.001-0.01 s−1. The validity of the calculations was confirmed by observing the microstructure of the 9Ni590B steel sample under the optimal thermal process parameters. [ABSTRACT FROM AUTHOR]

Hot compression behaviors of Pb-Mg-Al-B-0.4Y alloy under strain rate of 0.001-1 s−1 and temperature of 493-613 K were performed by employing hot compressing tests. According to the experimental stress–strain curves, as the strain increases, the flow stress increases firstly, then reaches the peak stress, and finally decreases to a steady state. Constitutive equations in traditional Arrhenius model and improved Arrhenius model in multi-linear regression were used to predict the flow stress of Pb-Mg-Al-B-0.4Y alloy. The values of MARE and RMSE in the traditional Arrhenius model are 11.780 and 21.169%, respectively, which are larger than 7.227 and 7.447% of the improved Arrhenius model, indicating that the predicted accuracy of the improved Arrhenius model is more accurate. The hot processing maps under the experimental conditions were established. Based on processing maps and microstructure observation, the optimum processing parameters are 0.001 s−1 ≤ ε ˙ ≤ 0.01 s−1 and 587 K ≤ T ≤ 613 K. [ABSTRACT FROM AUTHOR]

For improving production efficiency and saving energy, various manufacturing technologies for integrating solid-state joining and plastic forming processes have become hot topics in recent years. Hot deformation and solid-state bonding of materials are essences for the integration of solid-state joining and plastic forming processes. This study compared the hot deformation and solid-state bonding behavior of an Al-Mg-Si alloy at the temperatures ranging from 673 to 803 K and the strain rates ranging from 0.001 to 10 s−1 using conventional hot isothermal compression tests (CHICT) and hot isothermal compression bonding tests (HICBT). The flow stress behavior of the material during CHICT and HICBT was compared, and a constitutive equation was established based on the true stress-strain curves obtained from HICBT. The evolution of grain structure and bonding interface in the processes of hot deformation and solid-state bonding was investigated. Furthermore, the quantitative relationship between the interfacial bonding degree and the temperature and strain rate was established, and the relationship between the bonding degree and the mechanical properties of the welds was discussed. A new parameter, RSS, was proposed to evaluate the solid-state weldability of materials. [ABSTRACT FROM AUTHOR]

Low-carbon bainitic Nb–Ti micro-alloyed steel was used in the present study to investigate the high-temperature deformation behavior. The high-temperature compression was carried out on a thermal simulation machine with a temperature range of 800 °C–1200 °C and a strain rate of 0.1–15 s−1. Using work-hardening and softening mechanisms (dynamic recovery, dynamic recrystallization), a constitutive model was built on the basis of a newly proposed strain–stress relation, and flow stress at a strain rate of 0.5 and 10 s−1 was employed to test the established model. By means of comparing predicted and calculated results, the reliability of the model was proved, and the predictability of the flow stress model was also quantified in terms of root mean square error and average absolute relative error, which were calculated to be less than 11 MPa and 7.00%, respectively. These error estimators confirm the constitutive models based on the improved strain–stress relation and indicate an effective method to predict the high-temperature flow stress with high precision. [ABSTRACT FROM AUTHOR]

In this paper, the constitutive modeling and hot deformation behavior of SP-700 titanium alloy was investigated by performing isothermal hot compression tests in the temperature range of 700-950 °C and strain rates of 0.001, 0.1, and 1 s−1. The flow curves of the alloy indicated that the yield point phenomenon occurs at strain rates of 0.1 and 1 s−1. The friction, adiabatic heating, and stroke-rate controlling effects were eliminated from the raw data. Then, three types of phenomenological constitutive models, considering the compensation of strain, were used to predict the flow stresses of the alloy. The correlation coefficients (R2) of the measured and predicted results for the power-law, hyperbolic-sine law, and dynamic softening models were found to be 0.9790, 0.9883, and 0.9877, respectively. The corresponding average absolute relative errors (AARE) were 6.3, 5.9, and 7.45%, respectively. The flow softening behavior of SP-700 alloy was modeled using the combined hyperbolic-sine law and dynamic softening model approach. The predicted flow stresses were in a good agreement with the experimental data, indicated that the developed models can accurately characterize flow behavior of the alloy. In addition, the strain-rate sensitivity (m) distribution map of the alloy was obtained by plotting the m-value against temperature and strain rate in the form of a contour map. There was the maximum of m-value (0.36) in the temperature ranges of 700-715 and 837-875 °C, and strain rates of 0.001-0.006 s−1. The microstructure of hot deformed at 700 °C mainly consists of globularized and lamellar α phase, while dynamic globularization was completed at 800 °C. The hot deformation activation energy of the alloy in α/β region (305.5 kJ mol−1) was higher than that in single-phase β region (165.2 kJ mol−1) due to the globularization of lamellar α. [ABSTRACT FROM AUTHOR]

In this study, different existing stability/instability criteria (viz Prasad, Murty, Gegel, Alexander, Jonas, and Semiatin) are used to characterize the hot deformation instabilities of super-304H stainless steel. The instability maps are developed based on flow stress data acquired from uniaxial hot compression tests performed at various temperatures (1173-1423 K) and strain rates (0.001-10 s−1). The deformation instabilities are further validated through detailed microstructural observations. Flow localization and cracking have been identified as the signature of deformation instabilities in this alloy. The microcracks have been found to be associated with the grain boundary precipitation of coarse (~ 1- to 5-µm-sized) Nb-rich particles (mainly NbC). The instability criteria developed based on dynamic material modeling (i.e., Prasad's and Murty's criteria) could accurately predict the formation of microcracks in the entire hot deformation range employed in this study. Albeit the Gegel's and Alexander's stability criteria could correctly predict the flow localization, it has overestimated the deformation instabilities at high temperatures (> 1250 K) and low strain rates (≤ 0.1 s−1). In contrast, Jonas' and Semiatin's instability criteria have under-predicted the unstable domains in the studied alloy. [ABSTRACT FROM AUTHOR]

The hot deformation behavior of high-strength aluminum alloys AA7010 and AA 7075 was studied through hot isothermal compression testing in the temperature regime of 623-723 K (at an interval of 25 K) and at varying strain rates (0.001 to 10 s−1). The safe zone of hot workability of both the alloys was determined using the instability criteria and correlating with the microstructure evolution. Zener–Hollomon parameters were calculated, and constitutive equations were also derived. Common characteristics observed in both the alloys were adiabatic shear band formation at a temperature of 623 K and strain rate of 10 s−1 and flow localization at combination of all temperatures and high strain rate of 10 s−1 with evolution of very fine recrystallized (DRX) grains. High-temperature resistance to deformation, large extent of recrystallization and relatively larger zone of stable deformation and higher activation energy in Al alloy AA7010 were observed as compared to AA7075. Considering the role of precipitates, dynamic recrystallization was found to have significant role in governing the hot deformation behavior of the alloys. Prediction of constitutive equations was found to be more accurate at higher temperatures and at moderate-to-high strain rates with relatively less error in AA7075 alloy as compared to AA7010 alloy. [ABSTRACT FROM AUTHOR]

This study investigates the deformation behavior of a medium–high carbon Mn-Si-Cr alloyed steel using hot compression tests. The tests were performed on a Gleeble 1500D thermomechanical simulator with a temperature range of 950–1150 °C and a strain rate range of 0.005–5 s−1. The processing parameters (i.e., temperature T, strain rate ε ˙ , and strain ε) influenced the flow softening behavior of the material. The dynamic recrystallization occurred during hot deformation. Correlations between the Zener–Hollomon parameter and the size and the volume fraction of new recrystallized grains were developed. These findings are described using mathematical models. The strain-compensated Arrhenius-type constitutive model and the multiple-linear model were developed based on the true stress–strain curves we obtained. A comparative study was performed in order to measure the validity of the two models in representing hot deformation behavior. Both models were shown to accurately predict flow stress across a range of conditions, reflecting the characteristics of true stress–strain curves by exhibiting work hardening, dynamic recovery, and dynamic recrystallization. The empirical multiple-linear mathematical model was shown to be more efficient and accurate when calculating the hot deformation behavior of steel at elevated temperatures. [ABSTRACT FROM AUTHOR]

The hot deformation behavior of pure nickel with coarse, columnar grains in the temperature range of 950–1150 °C at intervals of 50 °C and in the strain rate range of 0.001–10.000 s−1 at intervals of one order of magnitude was investigated by isothermal hot compressive testing with the compression ratio of 70%. The results reveal that the strain rate and the temperature strongly affect the flow stress during hot deformation and that flow stress increases with the increase in strain rate while decreases with temperature increasing. Moreover, the relationship among flow stress, strain rate and temperature can be represented by the Zener–Hollomon parameter with the calculated apparent activation energy of 312.403 kJ·mol−1, and the variation of activation energy is sensitive to strain rate rather than temperature. In addition, the dynamic recrystallization (DRX) analysis reveals that the DRX behavior of nickel is evidently affected by both deformation temperature and strain rate and that the distinct mechanisms of nucleation are the bulging of serrated grain boundaries and the development of twinning. [ABSTRACT FROM AUTHOR]

In the present research, a series of double-stage hot compression tests were conducted in the temperature range of 950-1150 °C, strain rates in the range of 0.01-1 s−1, strain in the range of 0.1-0.3, and inter-pass time range of 3-100 s to evaluate the kinetics of the post-deformation recrystallization in AISI 321 austenitic stainless steel. An Avrami-type kinetics equation has been determined based on the obtained experimental data. Results show that the extent of post-deformation recrystallization increases with increase in inter-pass time, deformation temperature, pre-strain, and strain rate. The calculated activation energy for recrystallization (174 kJ/mol) is lower than the activation energy for static recrystallization of austenitic stainless steels. It is concluded that the both static and metadynamic recrystallization occurred during the inter-pass period. Also, the predicted softening fraction using the proposed kinetics equation agreed well with those obtained from experimental results. [ABSTRACT FROM AUTHOR]

Hot deformation tests of an upward continuous cast Cu-0.19Cr-0.1Ag were performed on a thermal simulation testing machine with various strain rates (0.01-10 s−1) at different deformation temperatures (750-950 °C) to investigate the microstructural evolution of hot deformation and the softening mechanism. From the results, a flow stress reduction ratio diagram was constructed. The diagram was divided into four regions with different softening mechanisms according to the stress-strain curve. Dynamic recrystallization was accompanied by two nucleation mechanisms: continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization, and the effect of CDRX decreased with increasing strain rate. [ABSTRACT FROM AUTHOR]

Objective: To explore the preventive effect of applying hot compress with Chinese herbal salt packets (CHSP) to puncture vessels under aseptic conditions during peripherally inserted central catheter (PICC) on postoperative phlebitis.Methods: A total of 720 hospitalized patients undergoing first PICC were assigned to treatment and control groups (360 cases each group) according to a random number table. The control group received conventional catheterization and nursing care. The treatment group was first given hot compress with CHSP (which consisted of honeysuckle 30 g, Semen brassicae 30 g, Salvia miltiorrhiza 30 g, Angelica dahurica 30 g, Semen raphani 30 g, Evodia rutaecarpa 30 g, and coarse salt 20 g) on the punctured vessel under aseptic conditions for 5-10 min before conventional catheterization. The main efficacy indices were the vessel diameters before and during catheterization and the success rate of a single catheter, and the secondary efficacy indiex was the incidence of superficial phlebitis within 1 week after catheterization.Results: The vessel diameter during catheterization of the treatment group was remarkably increased compared with the control group [(7.96±0.42) mm vs. (4.39±0.54) mm, P<0.01]. The success rate of the single catheter of the treatment group was significantly higher than that of the control group [94.00% (329/350) vs. 73.72% (244/329), P<0.01]. The incidence of superficial phlebitis within 1 week after catheterization in the treatment group was lower than that in the control group (P=0.007). There was no adverse event with CHSP.Conclusion: Hot compress with CHSP during PICC is applicable as it can effectively improve the success rate of a single catheter and reduce the incidence of superficial phlebitis after catheterization (Trial registration No. ChiCTR-ONC-17010498). [ABSTRACT FROM AUTHOR]

The hot deformation behavior of a high strength low carbon steel was investigated using hot compression test at the temperature range of 850-1100 °C and under strain rates varying from 0.001 to 1 s−1. It was found that the flow curves of the steel were typical of dynamic recrystallization at the temperature of 950 °C and above; at tested strain rates lower than 1 s−1. A very good correlation between the flow stress and Zener-Hollomon parameter was obtained using a hyperbolic sine function. The activation energy of deformation was found to be around 390 kJ mol−1. The kinetics of dynamic recrystallization of the steel was studied by comparing it with a hypothetical dynamic recovery curve, and the dynamically fraction recrystallized was modeled by the Kolmogorov-Johnson-Mehl-Avrami relation. The Avrami exponent was approximately constant around 1.8, which suggested that the type of nucleation was one of site saturation on grain boundaries and edges. [ABSTRACT FROM AUTHOR]

The main goal of this study is to investigate the microstructure and electrical properties of Al-Zr-La alloys under different hot compression deformation temperatures. In particular, a Gleeble 3500 thermal simulator was used to carry out multi-pass hot compression tests. For five-pass hot compression deformation, the last-pass deformation temperatures were 240, 260, 300, 340, 380, and 420°C, respectively, where the first-pass deformation temperature was 460°C. The experimental results indicated that increasing the hot compression deformation temperature with each pass resulted in improved electrical conductivity of the alloy. Consequently, the flow stress was reduced after deformation of the samples subjected to the same number of passes. In addition, the dislocation density gradually decreased and the grain size increased after hot compression deformation. Furthermore, the dynamic recrystallization behavior was effectively suppressed during the hot compression process because spherical AlZr precipitates pinned the dislocation movement effectively and prevented grain boundary sliding. [ABSTRACT FROM AUTHOR]

Hot compression tests on AZ40 magnesium alloy were conducted on a Gleeble 1500d hot simulation testing machine in a deformation temperature range of 330 °C-420 °C and a strain rate range of 0.002-2 s. Hot deformation behaviors were investigated on the basis of the analysis of the flow stressstrain curves, constitutive equation, and processing map. The stress exponent and apparent activation energy were calculated to be 5.821 and 173.96 kJ/mol, respectively. Deformation twins and cracks located in grain boundaries were generated at 330 °C and 0.02 s, which are associated with a high strain rate and a limited number of available slip systems. With increasing temperature and decreasing strain rate, the twins disappeared and the degree of dynamic recrystallization increased. The alloy was completely dynamically recrystallized at 420 °C and 0.002 s, with a homogenous grain size of approximately 13.7 μm. The instability domains of the deformation behavior can be recognized by processing maps. By considering the processing maps and characterizing the microstructure, the optimum hot deformation parameters in this experiment were determined to be 420 °C and 0.002 s. [ABSTRACT FROM AUTHOR]

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, 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. [ABSTRACT FROM AUTHOR]

A series of hot compression tests of medium carbon Cr–Ni–Mo-alloyed steel, 34CrNiMo steel, were conducted on a Gleeble-1500 thermal mechanical simulator, in a wide temperature range of 1173–1423 K and at a strain rate range of 0.002–5 s−1. Three constitutive models, namely the Johnson–Cook (JC) model, strain compensated Arrhenius model, and the physically based constitutive model, were established to describe the hot deformation of 34CrNiMo steel. A comparative study of the three models was investigated by comparing the accuracy of prediction of flow stress behavior. The results imply that the JC model is not able to adequately represent the high-temperature flow behavior with the existance of recovery and recrystallization. The Arrhenius-type model based on mathematics has a good prediction in the flow stress behavior in all strain ranges during the hot deformation. The physically based constitutive model gives a better prediction accuracy of the deformation behavior in both flow stress and deformation mechanism. [ABSTRACT FROM AUTHOR]

The predictability of modified constitutive model, based on Arrhenius type equation, for illustrating the flow behavior of Fe–36%Ni Invar alloy was investigated via isothermal hot compression tests. The hot deformation tests were carried out in a temperature range of 850–1100 °C and strain rates from 0.01 to 10 s−1. True stress-true strain curves exhibited the dependence of the flow stress on deformation temperatures and strain rates, which then described in Arrhenius-type equation by Zener–Holloman parameter. Moreover, the related material constants and hot deformation activation energy (Q) in the constitutive model were calculated by considering the effect of strain as independent function on them and employing sixth polynomial fitting. Subsequently, the performance of the modified constitutive equation was verified by correlation coefficient and average absolute relative error which were estimated in accordance with experimental and predicted data. The results showed that the modified constitutive equation possess reliable and stable ability to predict the hot flow behavior of studied material under different deformation conditions. Meanwhile, Zener–Holloman parameter map was established according to the modified constitutive equation and used to estimate the extent of dynamic recrystallization. [ABSTRACT FROM AUTHOR]

Isothermal and constant strain rate compression tests of as-homogenized Mg-5.9Zn-1.6Zr-1.6Nd-0.9Y alloy were performed by using Gleeble-3800 thermo-mechanical simulator at temperature between 523 and 723 K and strain rate range from 0.001 to 1 s, respectively. The deformation behavior of the alloy at elevated temperature was investigated. A strain-dependent constitutive model based on the Arrhenius model and back-propagation neural network (BPNN) model of the flow stress was established. The predictability of the two models was evaluated by average absolute relative error (AARE) and correlation coefficient ( R ), respectively. The results show that the BPNN model has more accurate predictability than strain-dependent constitutive model. Processing maps are obtained according to the principles of the dynamic materials modeling and microstructures of the compressed samples. The microstructure of the samples was observed by optical microscope and electron backscattered diffraction. Processing maps show that the instability domain is at a strain rate of range of 0.015-1 s and a temperature between 523 and 623 K. The alloy has good workability at 630-700 K and 0.008-0.1 s, wherein dynamic recrystallization occurs. [ABSTRACT FROM AUTHOR]

The metadynamic recrystallization (MDRX) behavior of a Nb–V microalloyed nonquenched and tempered steel was investigated by isothermal hot compression tests on Gleeble-1500 thermal-mechanical simulator. Compression tests were performed using double hit schedules at temperatures of 1273–1423 K, strain rates of 0.01–5 s−1, initial grain sizes of 92–149 μm and an inter-pass time of 0.5–10 s. The experimental results show that MDRX softening fraction increases with the increasing of deformation temperature, strain rate, and inter-pass time, while it decreases with the increasing of initial grain size. Based on the experimental results, the MDRX softening fraction kinetic model and recrystallized grain size model of the tested steel was established. Besides, using the above mathematic models, a finite element model was built to simulate the MDRX process of the tested steel. The simulation results show good agreement with the experimental ones, which indicates that finite element method is an effective approach to analyze the MDRX behavior and the established that mathematic models of the tested steel are reliable and accurate. [ABSTRACT FROM PUBLISHER]

The compressive deformation behavior of 95CrMo steel, one of the worldwide used hollow steels, was investigated on a Gleeble-3500 thermo-simulation machine within temperature range of 1073-1323 K and strain rate range of 0.1-10 s. Considering the influence of work-hardening, dynamic recovery and dynamic recrystallization, a new constitutive model for high-temperature flow stress was established in this paper. The calculated values predicted by the new constitutive model lie fairly close to the experimental values with a correlation coefficient ( R) of generally above 0.99 and an average absolute relative error of 3.00%, proving a good predictability of the new constitutive model. Also, a modified Sellars-Tegart-Garofalo model (STG model) was introduced to verify the precision of the new constitutive model. Compared to the modified STG model, the new constitutive model has a higher accuracy, which implies it is a reliable tool for predicting flow stress at high temperatures not only under equilibrium state, but also under transient deformation conditions. Besides, the new constitutive model was proved still viable in the initial stage of plastic deformation where plastic strain is lower than 0.05. [ABSTRACT FROM AUTHOR]

The metadynamic recrystallization (MDRX) behavior of a typical Ni-Cr-Mo-based superalloy Hastelloy C-276 was investigated using two-stage isothermal compression tests on a Gleeble thermal-mechanical simulator in the temperature range of 1050-1200 °C, the strain rate range of 0.1-5.0 s, the strains of 0.32, 0.45, and 0.6 at the first stage of compression, and the interval times of 0.5-30 s. The results show that the microstructure and the stress-strain relation of the studied superalloy vary during the interruption period due to the occurrence of MDRX. The MDRX softening fraction and recrystallized grain size increase rapidly with the increasing of interval time, deformation temperature, and strain rate. The effect of strain at the first stage of compression on MDRX is less pronounced. The kinetics of MDRX softening was established based on the flow stress curves, and the apparent activation energy of MDRX of Hastelloy C-276 is evaluated as 241 kJ/mol. [ABSTRACT FROM AUTHOR]

An important concern in hot working of metals is whether the desired deformation can be accomplished without fracture of the material. This paper builds a fracture prediction model to predict fracture initiation in hot compression of a burn-resistant beta-stabilized titanium alloy Ti-35V-15Cr-0.3Si-0.1C using a combined approach of upsetting experiments, theoretical failure criteria and finite element (FE) simulation techniques. A series of isothermal compression experiments on cylindrical specimens were conducted in temperature range of 900-1150 °C, strain rate of 0.01-10 s first to obtain fracture samples and primary reduction data. Based on that, a comparison of eight commonly used theoretical failure criteria was made and Oh criterion was selected and coded into a subroutine. FE simulation of upsetting experiments on cylindrical specimens was then performed to determine the fracture threshold values of Oh criterion. By building a correlation between threshold values and the deforming parameters (temperature and strain rate, or Zener-Hollomon parameter), a new fracture prediction model based on Oh criterion was established. The new model shows an exponential decay relationship between threshold values and Zener-Hollomon parameter (Z), and the relative error of the model is less than 15%. This model was then applied successfully in the cogging of Ti-35V-15Cr-0.3Si-0.1C billet. [ABSTRACT FROM AUTHOR]

The present study deals with the static and dynamic microstructural evolution of a high-Mn twinning-induced plasticity steel. Static recrystallization (SRX) is considered through cold rolling followed by annealing with different holding times. Dynamic recrystallization (DRX) was explored by hot compression tests at different temperatures and strain rates. The microstructural observations demonstrated that new grains nucleate at the prior grain boundaries and grain size decreased when cold rolling was followed by annealing. Additionally to the grain size reduction due to the SRX, nucleation sites for DRX increased. It is shown that flow stress level increased as a result of grain refinement caused by static and DRX. [ABSTRACT FROM AUTHOR]

The deformation process and inter-pass time of hot working are always accompanied by complicated microstructural evolution. As a kind of low alloy steels with good malleability, Q345E steel is widely used. The specimens of Q345E steel were heated to 1123, 1223, 1323, 1423, and 1523 K and held for 0, 120, 240, 360, and 480 s, respectively, on Gleeble-3500 thermo-mechanical simulator to develop the austenite grain growth equation of Q345E steel. In addition, the 'single-pass hot compression tests,' 'double-pass hot compression tests,' and 'single-pass hot compression and thermal insulation tests' at temperature from 1123 to 1423 K with the strain rate from 0.01 to 10 s were carried out on Gleeble-3500 thermo-mechanical simulator to investigate the behavior of dynamic recrystallization (DRX), meta-dynamic recrystallization (MDRX), and static recrystallization (SRX), and to establish the mathematical equations of DRX, MDRX, and SRX, which can predict the volume fraction of recrystallization and grain size after recrystallization. The result of error analysis and a 2D finite element simulation model during hot upsetting verifies that the experimental data agree well with the predicted values calculated by these mathematical equations, which indicates that the established mathematical equations can be applied to accurately predict the microstructural evolution of Q345E steel during hot deformation. [ABSTRACT FROM AUTHOR]