Flow Stress Strain Curves Research Articles

Leveraging machine learning to minimize experimental trials and predict hot deformation behaviour in dual phase high entropy alloys

In recent time, high entropy alloys (HEAs) are widely used due to their wide design space and remarkable properties allowing a vast range of property variations with myriads of possible combinations of constituent elements. This research utilizes machine learning techniques, including Random Forest (RF), K-Nearest Neighbors (KNN), XGBoost (XGB), Decision Tree (DT), and Support Vector Regressor (SVR), to predict the flow stress behavior of the dual FCC phase CoCrCu1.2FeNi high entropy alloy (HEA) at new temperature and strain rates to reduce the experiments dependency. The RF and KNN models were identified as top performers, with R² values of 0.987 and 0.986, respectively. These models successfully predicted flow stresses, aligning closely with actual measurements. A new flow stress-strain curve was generated at new temperature of 1123K, demonstrating good performance metrics for RF and KNN. with R² values of 0.97 and 0.958 respectively. This approach has the potential to significantly reduce the need for extensive experimental work in determining the mechanical behaviour of HEA, offering substantial savings in time, cost, and energy, and marks a significant advancement in the development of such alloys.

Thermo-mechanical processing characteristics and strain-rate-sensitive degradation properties of Mg-Er-Ni alloys

Hot deformation behavior, the corresponding microstructure evolution, and degradation properties of a weak-textured Mg-Er-Ni alloy containing a high-volume fraction of Ni-LPSO phases, have been investigated. Hot deformation behavior has been carried out in the temperatures range of 370 ∼ 460 °C and strain rates range of 0.001 ∼ 1 s−1. Flow stress-strain curves of high strain rate cases show a continuous increase trend without a steady or a peak stage, while that of low strain rate cases show an obvious dynamic softening after peak stress. Based on flow stress-strain curves, materials constants calculated by an Arrhenius-type constitutive equation, show a high n and Q compared to those of high-volume fraction α-Mg matrix Mg alloys. Optimal processing windows, based on the dynamic material model, is determined as high temperature domains. As for microstructure evolution, a complete recrystallization and dispersive Ni-LPSO fragments for high temperature & low strain rates while a restricted recrystallization and a streamline distribution LPSO phase for high temperature & high strain rates are observed. Varying degrees of continuous dynamic recrystallization, particle induced nucleation mechanism, as well as coordinated deformation of LPSO through kinking and bending account for the strain-rate-dependence hot deformation mechanism. As a result, dispersive Ni-LPSO fragments at low strain rates provide more degradation channels for the α-Mg matrix and thus possess better a degradation rate than the streamlined LPSO at high strain rates.

A comprehensive constitutive equation for the hot deformation of WC-Co

Hot deformation of five microstructurally different sintered WC-Co cemented carbides during hot compression testing was investigated in the temperature range of 700–1000 °C and at strain rates ranging from 0.0005 to 0.1 s−1. The stress-strain flow curves of the studied materials exhibited a peak followed by a fast drop in stress or sudden failure. A higher peak stress was achieved by decreasing the testing temperature, increasing the strain rate or lowering the amount of binder content. Constitutive equations were used to develop a useful physically based model describing the mechanical resistance of cemented carbides as a function of three different stress terms, representing stresses carried by the binder phase, accommodated by the carbide phase and associated with the interaction between the metallic and ceramic phases. The first term was modelled after the hot deformation of Co and was very small. The second one revealed an activation energy of Q = 585 kJ/mol, identified as that of W pipe diffusion in WC, and was barely dependent on the temperature and strain rate. Finally, the third stress contribution provided valuable insight on the role of the carbide skeleton in cemented carbides, proving the major effect of the microstructural arrangement in the deformation resistance. All the testing conditions were included in the model, with only a few extreme data points having to be excluded. Outcomes of the model were further supported by a thorough EBSD characterization.

A 90-meter Split Hopkinson Tension–Torsion Bar: Design, Construction and First Tests

AbstractThis article describes the design, construction, and first experimental results of a 90 m-long Hopkinson bar which can perform high strain rate tests in a combined tension–torsion state. The system configuration is analogous to the classic Hopkinson bar technique, consisting of three bars: a pre-stressed bar, an input bar, and an output bar; the sample is placed between the input and output bar. The measurement is also based on the classical three-wave method, where the incident, transmitted and reflected waves are measured. Incident compression and torsional waves are simultaneously generated by the failure of a fragile element that connects the pre-stressed bar to electromechanical actuators; the indirect Hopkinson tension bar technique is exploited, where the compression wave reaches the end of the output bar without stressing the sample and is reflected as a tensile input wave. The length of the bars is designed so that the tensile wave reaches the sample from the output bar side at the same time as the torsion wave comes from the input bar. Void tests were carried out first, for preliminary analysis of the system behaviour. Then, successful tests have been conducted on samples made of AA7075 T6, both in combined and pure tension–torsion states; it has been possible to measure the tension–torsion stress–strain curves, from which the equivalent flow stress–strain curve has been evaluated and compared to the quasi-static ones.

Change in deformation mechanism to change TRIP to TWIP strengthening in the class of 304 austenitic stainless steel sheets by trapezoidal wavy-rolling process

ABSTRACT Strengthening of steels through twinning-induced plasticity (TWIP) has several advantages like high-strength and high-ductility combination over the transformation-induced plasticity (TRIP) mechanism which gives high strength, low ductility and product phase of martensite in the single phase solid solution of austenitic matrix. But, development of TWIP effect will be more difficult unless the steel contains high stacking fault energy (SFE) (>20mJ/M2), fine grain structure and high manganese alloying (15–30 wt.%). These are very expensive processes and susceptible to metallurgical complexity in the austenitic stainless steels. Therefore, new processing technology was developed for strengthening of the austenitic stainless steel sheets by trapezoidal wavy rolling (TWR). Type 304 austenitic stainless steel was selected for this study which is known as martensite transformation, a dominant hardening mechanism due to low SFE and coarse grained structure. Wavy deformation-induced results have been studied through strain hardening behaviour by flow stress-strain curves and microstructural changes by atomic force microscope (AFM), and phase transformations by using X-ray diffractometer (XRD) analysis. It is found that this process introduced changes from TRIP to TWIP mechanism by forming plenty of mechanical twins and shear bands type structure at initial stage of deformations and partial martensite is observed in advanced stage.

Portevin-Le Chatelier characterization of annealed Al-Mg alloy sheets with different Mg contents

The stress-strain flow curves of solid solution treated and annealed Al-(2.86-9.41)Mg aluminum alloy sheets were investigated during tensile process at room temperature at a strain rate of 1 × 10−3 s−1, in order to reveal the effect of solute Mg atoms and β-phase nanoparticles in the α-Al matrix on their Portevin-Le Chatelier (PLC) characteristics. The results show that with the increase of Mg contents of alloys, the concentration of solute Mg atoms and the volume fraction of β-phase nanoparticles in the α-Al matrix of the annealed alloy sheets increase. The β-phase nanoparticles promote the PLC effect during the tensile process, causing the increase of stress drop amplitude Δσ of the tensile curves of the alloy sheets. However, the β-phase nanoparticles have little influence on the strain period ΔεTmax of rectangular waves. The flow strain difference Δεc−σ between the yield point and the beginning of PLC effect decreases monotonically from 5.4 × 10−4 to 5 × 10−5 as the Mg contents of alloy sheets increase from 2.86 wt.% to 9.41 wt.%. The strain period ΔεTmax of the rectangular waves corresponding to the high flow stress and stress drop amplitude Δσ obtained for the serrated stress-strain curves of the alloy sheets gradually increase with the increasing Mg contents of alloy sheets.

Hot deformation behaviour of sintered cobalt

Hot deformation of sintered cobalt during hot compression testing was investigated in the temperature range of 700–1000 °C and at strain rates ranging from 0.0005 to 0.1 s−1. Cobalt underwent considerable dynamic recrystallization (DRX) during hot deformation, with stress-strain flow curves exhibiting one or several peaks followed by significant flow softening and leading to a steady-state stress. Constitutive equations were used to derive the flow stress behaviour. A physically based model to describe the strain rate as a function of stress was suggested for temperatures ranging between 775 and 1000 °C. In this case, a creep exponent (n) of 5 indicated that the deformation mechanism was controlled by the glide and climb of dislocations. The activation energy coinciding with the one for self-diffusion of ferromagnetic cubic cobalt implied a diffusion-controlled mechanism and the presence of face-centered cubic (FCC) cobalt during deformation. Interestingly, the results at 700 °C could not be perfectly fitted to this model and exhibited a higher resistance to deformation. This revealed that the glide and climb deformation mode was close to the transition where glide mode was dominant, and thus mostly glide occurred at 700 °C, especially for the largest strain rates.

Hot deformation behavior of a Fe3Al–Ta alloy in the B2-order regime

In the present work, the hot deformation behavior and the corresponding microstructure evolution of an Fe–25Al-1.5Ta (at.%) alloy in the B2-phase field were investigated. Uniaxial compression tests were carried out in a strain rate range from 0.0013 s−1 to 1 s−1 and in a temperature range from 800 °C to 850 °C, where an ordered B2–FeAl matrix phase along with a C14 - (Fe, Al)2Ta Laves phase was confirmed by X-ray diffraction. A dynamic material model was applied to predict the safe and damaging processing windows. The underlying flow softening mechanisms were characterized using scanning electron microscopy and electron-backscatter diffraction. The flow stress-strain curves mostly showed a broad maximum followed by a slight decrease in stress until a steady stress was reached. The optimum processing window for the studied alloy was located at 850 °C/0.0013 s−1, where the efficiency of power dissipation (η) and strain rate sensitivity (m) reached 50% and 0.25, respectively. The processing map also showed a domain of flow instability, resulting from cracking, in the range of lower temperatures and higher strain rates (800 °C/1 s−1). The microstructural analyses confirmed a combination of dynamic recovery (DRV) and dynamic recrystallization (DRX) over the entire range of deformation conditions tested. The current study reveals a well-suited parameter range to achieve a high degree of hot deformability in Fe–Al alloys at significantly lower temperatures than those typically used. This may contribute to optimizing the thermomechanical processing of Fe–Al alloys and reducing energy consumption in industrial forging operations.

Microstructure simulation and experiment investigation of dynamic recrystallization for ultra high strength steel during hot forging

In this paper, the flow behavior and evolution of microstructure during the hot forging process are predicted using numerical simulation, providing a reference for optimizing the process. The flow stress-strain curve of 30Cr2Ni3MoV steel was obtained by conducting hot compression experiments using Gleeble-3500 thermal simulator. The constitutive and dynamic recrystallization (DRX) cellular automaton (CA) models were established by analyzing the thermal deformation behavior, considering work hardening and DRX softening. This model was optimized by combining the dislocation density difference drive mechanism, increasing the total number of grain orientations, and then implementing Hash mapping to obtain the actual grain orientation. The simulation results of strain and strain rate in the process of thermal deformation were obtained through the constitutive model. Compared with the results of the hot compression experiment and the metallographic experiment, the accuracy of the simulation results of the DRX CA model was verified. Finally, the real-time updating module of deformation parameters is established, and the real-time process parameters of deformation calculation are updated to the CA model. The simulation results are consistent with the experimental results through metallographic experiments.

Hot Workability Investigation of an Fe-Al-Ta Alloy Using Deformation Processing Maps

Fe-Al-Ta alloys are expected to replace high-alloyed steels in steam turbine blades. However, the mechanical properties of the forged blades are still not optimal due to limited grain refinement during hot forging and the coarse-grained microstructure inherited from the as-cast precursor. It is, therefore, essential to investigate the hot deformation behavior of the alloy to identify the optimum range for the deformation parameters leading to good hot workability with significant grain refinement. The hot deformation behavior and hot workability of an Fe-25Al-1.5Ta (at.%) alloy were investigated in the present work using constitutive modeling and the concept of processing maps. Uniaxial compression tests were conducted in a strain rate range from 0.0013 s−1 to 1 s−1 and in a temperature range from 900 °C to 1100 °C, where a disordered A2 α-(Fe, Al) matrix phase along with a C14-(Fe, Al)2Ta Laves phase were confirmed by X-ray diffraction. The flow stress–strain curves showed a broad maximum followed by a slight drop in stress until a steady state was reached. The optimum processing window for the studied alloy was located at 910–1060 °C/0.0013–0.005 s−1, where the efficiency of the power dissipation (η) and strain rate sensitivity (m) reached 50% and 0.33, respectively. The material underwent a combination of dynamic recovery and dynamic recrystallization over the whole tested deformation range. No flow instabilities were predicted based on Prasad’s flow instability criterion when deformation was performed up to a true strain of 0.5 and 0.8, indicating a high degree of hot workability of the studied alloy over the entire deformation range tested. The current study reveals a well-suited parameter range for the safe and efficient deformation of Fe-Al-Ta alloys, which may contribute to the optimization of the thermomechanical processing of this alloy.

Comparative Study on Hot Metal Flow Behaviour of Virgin and Rejuvenated Heat Treatment Creep Exhausted P91 Steel

This article reports on the comparative study of the hot deformation behaviour of virgin (steel A) and rejuvenated heat treatment creep-exhausted (steel B) P91 steels. Hot uniaxial compression tests were conducted on the two steels at a deformation temperature range of 900–1050 °C and a strain rate range of 0.01–10 s−1 to a total strain of 0.6 using Gleeble® 3500 equipment. The results showed that the flow stress largely depends on the deformation conditions. The flow stress for the two steels increased with an increase in strain rate at a given deformation temperature and vice versa. The flow stress–strain curves exhibited dynamic recovery as the softening mechanism. The material constants determined using Arrhenius constitutive equations were: the stress exponent, which was 5.76 for steel A and 6.67 for steel B; and the apparent activation energy, which was: 473.1 kJ mol−1 for steel A and 564.5 kJmol−1 for steel B. From these results, steel A exhibited better workability than steel B. Statistical parameters analyses showed that the flow stress for the two steels had a good correlation between the experimental and predicted data. Pearson’s correlation coefficient (R) was 0.97 for steel A and 0.98 for steel B. The average absolute relative error (AARE) values were 7.62% for steel A and 6.54% for steel B. This study shows that the Arrhenius equations can effectively describe the flow stress behaviour of P91 steel, and this method is applicable for industrial metalworking process.

Kinetics and microstructure evolution of dynamic recrystallization of medium-Mn steel during hot working

The dynamic recrystallization (DRX) behavior and microstructure evolution of medium-Mn (0.15C–10Mn) steel were investigated through isothermal hot compression tests. The flow stress–strain curves and microstructure analysis, in wide ranges of temperatures (900–1150 °C) and strain rates (10−3 - 1 s−1), were employed to establish constitutive equations and a grain size evolution model. Since the material constants were calculated based on polynomial function of strains, strain compensation was introduced into constitutive analysis. Comparison and verification showed that the constitutive equation had a high predictive ability. The correlation coefficient and average absolute relative error were 0.99 and 4.46%, respectively, which confirm the accuracy and guidance of the model. Metallographic observation was used to implement the grain size evolution analysis of the medium-Mn steel. Microstructure evolution was characterized with a gradual increase in average recrystallized grain size and an obvious expansion in the range of grain size distribution with both deformation temperature and strain rate, which were attributed to the competition between nucleation and grain boundary migration. Besides, a grain size evolution model was established to analyze the microstructure evolution.

An Experimental and Numerical Study on Aluminum Alloy Tailor Heat Treated Blanks

Information is presented on the conceptualization, experimental study, and numerical process simulation of tailor heat treated aluminum alloy blanks. This concept is intended to improve the forming behavior of aluminum parts in challenging conditions. The implementation requires precise control of laser heat treatment parameters within a suitable industrial framework. The study details material properties, heat treatment parameters, and experimental results for the strength and elongation properties of an AA6063-T6 aluminum alloy. Constitutive modeling is applied using the Hocket–Sherby equation, which allowed us to establish a correlation between laser heat treatment maximum temperature and the corresponding material softening degree. Based on the generated flow stress–strain curves, a numerical simulation of a representative case study was performed with Abaqus finite element software highlighting potential improvements of tailor heat treated blanks (THTB). The influence and effectiveness of heat-affected zone (HAZ) dimensions and material softening were analyzed.

Flow behavior analysis and prediction of flow instability of a lamellar TA10 titanium alloy

The flow behavior analysis and prediction of flow instability of TA10 titanium alloy were investigated during isothermal compression. TA10 titanium alloy was prepared by an electron beam cold hearth, and the TA10 titanium alloy ingot had a lamellar structure. The ingots were subjected to isothermal compression by a Gleeble-1500 thermomechanical simulator at 800–1050 °C, the strain rate range was 0.01–1 s −1 and the height reduction was 60%. An analysis of the flow stress-strain curves showed that discontinuous yielding behaviors occurred when the deformation temperature exceeded the β-transus temperature, and flow softening occurred at all deformation temperatures except 900 °C. The sample microstructure was studied, and the microstructural evolution was summarized. When the deformation temperature was 950 °C and the strain rate was 1 s −1 , an adiabatic shear band appeared in the microstructure, and the element distribution in the adiabatic shear band was analyzed. Based on the dynamic material model, processing maps under Prasad's and Murty's instability criterion were established. Combined with the microstructure and instability situation, the applicability of Prasad's instability criterion in lamellar TA10 titanium alloy was clarified. The suitable processing parameters were 1020–1050 °C and 0.1–1 s −1 or 875–950 °C and 0.01–0.05 s −1 . Combined with electron back-scattered diffraction, the flow-softening mechanism was analyzed, and the results revealed that the lamellar kinking, deformation heat and dynamic recovery were the flow-softening mechanisms when the deformation temperature was lower than the β-transus temperature, and when the deformation temperature exceeded the β-transus temperature, the dynamic recovery was only the flow-softening mechanism. • The microstructural evolution, flow stress-strain curves and flow-softening extent were analyzed in detail. Only one flow instability was found and the type of flow instability was the adiabatic shear band. • The flow instability was predicted by establishing Prasad's and Murty's processing maps and the accuracy of the process maps was compared. • Combined with the flow-softening extent, the flow-softening mechanism was analyzed by EBSD in detail. The flow-softening mechanism changed with deformation temperatures and strain rates.

Understanding hot workability of power plant P92 creep resistant steels using dynamic material modelling (DMM) and microstructural evolution

This study reports the hot workability of two P92 creep-resistant steels with different chromium and tungsten contents, all within the ASME specification. These steels are used in manufacturing modern power plant boiler pipes. Uniaxial compression tests were done using a Gleeble® 3500 thermal-mechanical equipment. The test conditions were: deformation temperature of 850–1000 °C and strain rate of 0.1–10 s−1. Experimental flow stress values obtained from isothermal hot compression tests were used to construct processing maps employing the dynamic material model approach. The flow stress-strain curve results of the two steels exhibited dynamic recovery characteristics. The flow stress increased with a decrease in temperature or an increase in strain rate. The correlation between the processing maps and the microstructure of the deformed samples reveals that the optimal processing window for the two steels occurred at a deformation temperature of 850 °C and 1000 °C and a lower strain rate of 0.1 s−1 for the conditions studied. These regions had maximum power efficiency of 26% (P92-A steel) and 19% (P92-B steel). The findings from this study have provided a new approach to process parameter optimisation using a dynamic material model technique of industrial metal forming of P92 steels. Hence, reducing manufacturing time and cost.

Hot deformation behavior and microstructure evolutions of as-forged Mg-Gd-Y-Zn-Zr alloy

The hot deformation behavior of Mg-9.16Gd-3.03Y-1.44Zn-0.61Zr alloy was examined by hot compression experiments at 623–753 K with strain rates 0.1–20 s−1. Flow stress-strain curves developed an Arrhenius-type equation with adjustment for strain. The influence of strain on microstructure evolution was studied by optical microscope. The results showed that with the increase of deformation, LPSO phase broken and kinked and interacted with dislocations to promote nucleation of dynamic recrystallization (DRX) grains. In addition, the effects of temperature and strain rate on DRX during hot compression were examined using electron back-scatter diffraction. The results demonstrated that the volume fraction of DRX grains improved as temperature and strain rate increased. The alloys could adapt to plastic deformation caused mostly by continuous and discontinuous dynamic recrystallization. Transmission electron microscopy was then utilized to observe the phase structure. The dynamic precipitates occurred after hot compression, and the LPSO phase was broken and kinked, which coordinated the plastic deformation. Using the Avrami equation, the DRX dynamic model of the alloy at 0.1 s−1 was established for the first time.

Prediction and Validation of Stress Triaxiality Assisted by Elasto-Visco-Plastic Polycrystal Model

The ΔEVPSC numerical code based on the elasto-visco-plastic HEM (Homogeneous Effective Medium) provides a multiscale constitutive modeling framework that is suitable for describing a wide range of mechanical behaviors of polycrystalline metals. In this study, an AA6061-T6 aluminum sample was chosen to validate the predictive capability of the ΔEVPSC stand-alone (ΔEVPSC-SA) code on stress triaxiality and its evolution until fracture. The model parameters were calibrated by fitting the uniaxial flow stress-strain curve, and the initial crystallographic orientation distribution (COD) was obtained using X-ray diffraction and electron backscattered diffraction (EBSD) methods. The statistical representativeness of the COD was further examined by comparing the experimental R-values with model predictions based on a set of CODs obtained via the two mentioned diffraction methods. The results suggest that the X-ray scan does not represent the texture very well, and instead, an entire cross-sectional EBSD scan is required, even though the texture gradient along the through-thickness direction is not very significant. The model-calculated triaxiality based on the ΔEVPSC-SA code was verified by comparison with the experimental results from the uniaxial tension, the notched tension, and the plane strain tests. The results were in good agreement with the ΔEVPSC finite element (FE) simulation results and other similar experimental results reported in the literature.

The interrupted hot compression of an as-forged titanium matrix composite: flow softening behavior and deformation mechanism

In this paper, the deformation behavior and microstructure evolution of 2.5vol.% (TiBw + TiCp)-containing high-temperature titanium matrix composite (TMCs) was studied by the interrupted compression tests. The flow stress–strain curves of reloading of TMCs showed the flow softening behavior. The decrease of flow stress was associated with increasing holding time and deformation temperature or decreasing strain rate. The static softening mechanism was associated with the DRV, DRX and consume of dislocations during interrupted holding (SRV) reflected by the Q, n and microstructure. The fraction of αp phase decreased with increased holding time and deformation temperature or decreased strain rate. Due to the transformation of αp phase to β phase, the high-temperature deformation ability of the TMCs will be improved a lot, which is consistent with the decreased flow stress. For the reinforcements and αp phases, they played restricted role in the growth of α/β colonies. However, the decrease of αp phase made the grown up of α/β colonies in low strain rate. The deformation mechanism of the composites was cDRX caused by the transformation of LABs into HABs by progressive lattice rotation of α phase in (α+β) region and dDRX attributed to the nucleation and growth process of β grains in β region. Due to the addition of reinforcements, the weaken microtexture of composite can be obtained. After the interrupted compression, the optimal deformation parameter has been found for the TMCs, which can give guidance for the subsequent hot-working.

Dynamic Ferrite Formation and Evolution above the Ae3 Temperature during Plate Rolling Simulation of an API X80 Steel

Thermo-mechanically controlled rolling is a technique used to produce steel strips and plates. One of the steels widely used in the production of heavy plates for application in oil and gas pipelines is API X80. The hot rolling process of this family of steels consists of applying deformation passes at high temperatures, mainly above Ae3, inside the austenite phase field. It has been shown that during deformation, the phenomenon of dynamic transformation (DT) of austenite into ferrite leads to lower hot deformation resistance within the stable austenite region. In this investigation, hot torsion simulations of an industrial rolling process under continuous cooling conditions were used to monitor the formation of ferrite by DT. Stress–strain flow curves and equivalent mean flow stresses followed by sample characterization via optical and electron microscopy showed the inevitable formation of ferrite above the Ae3. The employed 10-pass deformation schedule was divided into 5 roughing and 5 finishing passes, thereby promoting an increased volume fraction of ferrite and decreased critical strain for the onset of DT and dynamic recrystallization (DRX). A microstructural analysis confirmed the formation of ferrite from the first roughing strain until the last finishing pass. The volume fraction of DT ferrite increased due to strain accumulation, an increased number of deformation passes and as the temperature approached the Ae3, leading to a characteristic torsion texture at the end of the simulation.

Metal flow behaviour and processing maps of high heat resistant steel during hot compression

This article reports the flow stress behaviour of ASTM A335 P92 steel. Uniaxial isothermal compression experiments were conducted to examine the hot deformation behaviour of P92 steel in a Gleeble® 3500 thermal–mechanical simulator. The test conditions were 0.01–10 s−1 strain rate and 850–1000 ℃ deformation temperature. Constitutive equations and processing maps developed were used to describe the hot deformation process. The results showed that the flow stress–strain curves exhibited a dynamic recovery (DRV) behaviour as the dominant softening mechanism. The flow stress decreased with an increase in the deformation temperature or a decrease in strain rate. Using the Arrhenius equation, the stress exponent and the activation energy values were 8.0 kJ.mol−1 and 487.56 kJ.mol−1, respectively. The correlation between the constructed processing maps and microstructure showed that the optimal process parameters occurred at a lower strain rate in the region of 0.1 s−1 and deformation temperatures of 900–950 ℃ and 1000 ℃ for the steel investigated.