Deformation Behavior Of Alloy Research Articles

Investigation on dynamic deformation behavior of 7A75 aluminum alloy over wide strain rates and constitutive model establishment

The aluminum alloy components on automobile often experience high strain rate deformation during accidents. The dynamic deformation behavior and constitutive model are crucial for analysis of vehicle body collisions and failures. In this work, the 7A75 aluminum alloy plate was heat treated according to standard body manufacturing procedures. Quasi-static and dynamic tensile experiments were conducted on the aged 7A75 alloy in a wide strain rate range from 0.001 s−1 to 500 s−1. The dynamic deformation behavior of the alloy was revealed, and the constitutive models were established. It was found that the 7A75 alloy has strong strain rate sensitivity, and its mechanical properties can be significantly improved with the increase of strain rate. As the strain rate increases, the necking instability strain shifts towards higher values, which leads to a larger uniform deformation ability and fracture elongation. This behavior results in a better energy absorption capacity at high strain rates, thus providing a good collision protection property. The constitutive models, including Johnson-Cook (J-C) and Zerilli-Armstrong (Z-A) types, were established and compared. Note that the conventional J-C and Z-A models exhibit severe prediction distortion. Therefore, a modified J-C model incorporating strain rate compensation was introduced, which decrease the errors by 149% and achieves accurate predictions of both dynamic and static deformation behaviors over a wide range of strain rates.

Flow stress behavior, constitutive modeling, processing map and microstructure evolution in hot deformation of Fe-7.1Al-0.7Mn-0.4C-0.3Nb alloy

The automotive industry has experienced rapid growth, with lightweight materials becoming a significant research focus. Among these materials, low-density Fe–Mn–Al–C alloys show promise for this kind of application. To optimize the hot workability parameters of these alloys for practical applications, it is essential to explore the hot deformation behavior of these alloys. In this study, we investigated the hot deformation behavior of the low-density alloy Fe-0.77Mn-7.10Al-0.45C-0.31Nb using hot plane-strain compression tests for several deformation temperatures (850, 950, 1050, and 1150 °C) and nominal strain rates (0.01, 1, and 10 s−1). Unusual flow stress curves were observed for low (0.01 s−1) and intermediate (1 s−1) strain rates, with discontinuous yielding and multiple stress peaks. This high-temperature behavior is associated with non-homogeneous strain partitioning in duplex microstructure (δ-ferrite + γ). Using the Zenner-Hollomon constitutive modeling approach, we estimated the thermal activation energy for hot deformation as 297 kJ/mol from the experimental peak flow stresses. Additionally, processing maps and microstructure correlation analysis revealed that the alloy exhibits good hot workability in the 975–1075 °C temperature range under low and intermediate strain rates (0.01–0.3 s−1). Under these processing conditions, the δ-ferrite microstructure is submitted to dynamic recovery, while the austenitic phase undergoes dynamic recrystallization.

Accurate simulation of texture evolution and mechanical response of cubic and hexagonal structural alloys using self-consistent polycrystal plastic method

Simulating the evolution of microstructures and the mechanical response of alloys with cubic and hcp structures is crucial for the industrial manufacturing of key alloy components. In this work, a modified Voce (ME-Voce) model is proposed, based on the extended Voce hardening model, to depict the variations of hardening rate with cumulative shear strain. Also, an orientation-dependent weight that describes the neighboring grain-induced ‘drag’ effect is evaluated. These improvements are numerically implemented in a standard viscoplastic self-consistent (VPSC) model. The ME-Voce parameters are determined through multi-parameter optimization using Matlab software. The influences of grain shape and neighboring grains on the hot deformation behavior of alloys are investigated. The proposed ME-Voce model is validated through hot compression experiments of alloys with cubic and hcp structures. The results show the VPSC embedded in the ME-Voce can reasonably predict the mechanical response under different deformation conditions. This enhances the predictive capability of the VPSC model and provides more options for crystal plasticity simulation of alloys with different crystal structures.

High-temperature deformation behaviour and processing map of near eutectic Al–Co–Cr–Fe–Ni alloy

The high-temperature deformation behaviour of near-eutectic high entropy alloy was studied at 800–1100 °C and 0.01–10 s−1. The microstructure of the as-cast alloy depicted a proeutectic L12 phase and epitaxially grown eutectic colonies of lamellar L12 and B2. Deformation temperature and strain rate played vital roles in defining the precipitation and deformation behaviour of the alloy. The lower-temperature deformed samples were characterized by extensive deformation twinning and strain accumulation. In contrast, high-temperature deformation led to uniform deformation with dynamic recrystallization, recovery, B2 lamellar fragmentation and B2 precipitation. The microstructure of the deformed samples corresponded well with the processing maps developed via dynamic materials model. The processing zones for the alloy were identified to be 800–950 °C and 10−2 – 10−1.25 s−1 as well as 925–1100 °C and 10−2 – 10−0.5 s−1. The critical material flow parameters displayed a complex relationship with temperature, strain rate and strain. In the studied temperature and strain rate regime, the critical strain rate was determined to be 0.1s−1. At strain rates above and below this value, the critical strain for recrystallization was higher. Within the studied temperature and strain rate regime, the near eutectic alloy displayed superior compressive strength and wider thermos-mechanical processing region than its eutectic counterpart.

Investigation of deformation behavior of Mg-2Ho alloy based on hyperbolic sine constitutive equation and PSO-BP neural network

In this study, uniaxial hot compression experiments were conducted on as-cast Mg-2Ho binary alloy that had undergone heat treatment. The hot deformation behavior of the alloy and the influence of strain rate (0.001–1 s−1) and deformation temperature (300–450 °C) on the mechanical properties were systematically studied. The microstructure and dynamic recrystallization (DRX) mechanisms of the alloy were analyzed in detail using scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) techniques. A strain-compensated Arrhenius constitutive equation based on Zener-Hollomon parameter and a particle swarm optimization-backpropagation artificial neural network (PSO-BP ANN) based on machine learning (ML) were established to study the flow behavior of the alloy. The experimental results demonstrate that the flow stress decreases with increasing temperature and/or decreasing strain rate. The elevated temperature promotes the occurrence of DRX, resulting in a softening behavior observed in the stress-strain curve. The DRX mechanisms for alloys primarily involve continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX). Further evaluation was conducted by using the correlation coefficient (R2) and mean squared error (MSE) to assess the constitutive equation and PSO-BP ANN. The prediction accuracy of the constitutive equation is poor (R2 =0.924), whereas the measured flow stress and predicted flow stress by PSO-BP ANN exhibit good consistency (R2 =0.99948), making it widely applicable for analyzing and predicting the hot deformation behavior of Mg-2Ho alloy under different experimental conditions.

The effect of stacking fault energy on the formation of nano twin/HCP during deformation in FCC concentrated solid solution (CSS) alloys

The exceptional mechanical properties of face-centered cubic (FCC) concentrated solid solution (CSS) alloys generally correlate various deformation mechanisms, such as deformation induced nano twins and/or hexagonal close packed (HCP) phases, which is normally determined by stacking fault energy (SFE). To systemically change the SFE but keep the influence of atomic size and modulus mismatches minimum, a series of NiCo-based alloys are designed by adjusting the Ni/Co ratio. All alloys are fabricated to be single phase FCC with grain size carefully controlled to be ∼60 μm. Deformation substructures after tensile tests over temperature ranging from 77 K to 1073 K are carried out to reveal the effect of SFE on mechanical properties and deformation mechanism. SFE has little effect on yield strength (YS) at all test temperature, but do affect the ultimate tensile strength (UTS) and elongation to fracture (EF) of the alloys. At temperature lower than 873 K, it seems that the lower the SFE, the higher the UTS. At 1073 K, there is no obvious trend for UTS and EF, indicating that SFE has little effect on deformation behavior of alloys at high temperature. Formation of deformation nano twin/HCP depends on not only the SFE of the alloys but also the temperature. As testing temperature and/or SFE of the alloys decreases, deformation induced nano twin/HCP are favorable and become dominant deformation modes for the FCC CSS alloys, resulting in a combination of high strength and good plasticity due to the great work hardening capacity.

Hybrid Artificial Neural Network-Based Models to Investigate Deformation Behavior of AZ31B Magnesium Alloy at Warm Tensile Deformation.

The uniaxial warm tensile experiments were carried out in deformation temperatures (50-250 °C) and strain rates (0.005 to 0.0167 s-1) to investigate the material workability and to predict flow stress of AZ31B magnesium alloy. The back-propagation artificial neural network (BP-ANN) model, a hybrid models with a genetic algorithm (GABP-ANN), and a constrained nonlinear function (CFBP-ANN) were investigated. In order to train the exploited machine learning models, the process parameters such as strain, strain rate, and temperature were accounted as inputs and flow stress was considered as output; moreover, the experimental flow stress values were also normalized to constructively run the neural networks and to achieve better generalization and stabilization in the trained network. Additionally, the proposed model's closeness and validness were quantified by coefficient of determination (R2), relative mean square error (RMSE), and average absolute relative error (AARE) metrics. The computed statistical outcomes disclose that the flow stress predicted by both GABP-ANN and CFBP-ANN models exhibited better closeness with the experimental data. Moreover, compared with the GABP-ANN model outcomes, the CFBP-ANN model has a relatively higher predictability. Thus, the outcomes confirm that the proposed CFBP-ANN model can result in the accurate description of AZ31 magnesium alloy deformation behavior, showing potential for the purpose of practicing finite element analysis.

Deformation behavior and strengthening effects of an eutectic AlCoCrFeNi2.1 high entropy alloy probed by in-situ synchrotron X-ray diffraction and post-mortem EBSD

In this work, high energy synchrotron X-ray diffraction was used during tensile testing of an as-cast eutectic AlCoCrFeNi2.1 high entropy alloy. Aside, from determining for the first time the volume fractions of existing phases, we further detail their role on the alloy deformation behavior. The two major phases, a soft disordered FCC and a hard ordered B2 BCC, were observed to exhibit a stress partitioning effect which can be used to modulate the mechanical response of the material based on the relative volume fraction of each phase. Dislocation density analysis revealed that the soft FCC phase had a significantly higher dislocation density right after the onset of plastic deformation. This is attributed to the existence of strain gradients across the lamellar structure, where the hard B2 BCC prevents free deformation of the FCC phase. Nonetheless, despite the increase of the dislocation density in the soft FCC phase, calculations of the strengthening effects induced by generation of dislocations are more significant in the hard B2 BCC phases, as this phase is primarily responsible for the strength increase in the alloy. Besides, the evolutions in dislocation density of the soft FCC and hard B2 BCC phases during tensile deformation obtained from synchrotron X-ray diffraction data are consistent with the evolution of KAM determined by EBSD characterization. Also, lattice strain analysis across two principal directions (parallel and perpendicular to the loading axis) reveals that for these specific orientations there is a preferential deformation of the hard FCC planes which can be related to the deformation response of specific lattice planes at distinct orientations, as well as to the phase partitioning stress behavior.

High Temperature Deformation Behavior of Near-β Titanium Alloy Ti-3Al-6Cr-5V-5Mo at α + β and β Phase Fields

Most near-β titanium alloy structural components should be plastically deformed at high temperatures. Inappropriate high-temperature deformed processes can lead to macro-defects and abnormally coarse grains. Ti-3Al-6Cr-5V-5Mo alloy is a near-β titanium alloy with the potential application. The available information on the high-temperature deformation behavior of the alloy is limited. To provide guidance for the actual hot working of the alloy, the flow stress behavior and processing map at α + β phase field and β phase field were studied, respectively. Based on the experimental data obtained from hot compressing simulations at the range of temperature from 700 °C to 820 °C and at the range of strain rate from 0.001 s−1 to 10 s−1, the constitutive models, as well as the processing map, were obtained. For the constitutive models at the α + β phase field and β phase field, the correlated coefficients between actual stress and predicted stress are 0.986 and 0.983, and the predictive mean relative errors are 2.7% and 4.1%. The verification of constitutive models demonstrates that constitutive equations can predict flow stress well. An instability region in the range of temperature from 700 °C to 780 °C and the range of strain rates from 0.08 s−1 to 10 s−1, as well as a suitable region for thermomechanical processing in the range of temperature from 790 °C to 800 °C and the range of strain rates from 0.001 s−1 to 0.007 s−1, was predicted by the processing map and confirmed by the hot-deformed microstructural verification. After the deformation at 790 °C/0.001 s−1, the maximum number of dynamic recrystallization grains and the minimum average grain size of 17 μm were obtained, which is consistent with the high power-dissipation coefficient region predicted by the processing map.

Microstructure evolution, tensile properties and internal structure transformation study on Ti6Al4V–5Cu anti-bacterial alloy during uniaxial tensile straining at low forming temperature

The tensile behavior of Ti6Al4V–5Cu alloy studied in the temperature range of 450–550 °C at the strain rate interval of 10−3-10−1 s−1. Alloy deformation behavior, microstructure evolution, and its relative internal structure changes due to deformation were investigated. The tensile behavior of the alloy had elucidated in terms of change in true stress-strain relationship. At 450 °C, the alloy showed the decrease of peak stress at the strain rate interval of 10−3-10−2 s−1, which suggests Ti6Al4V–5Cu plastic flow behavior, was quite different. The alloy exhibited an elongation (El) of 28% at 450 °C in a strain rate of 10−3 s−1. At 10−3 s−1, the El of the alloy decreased with the increase of forming temperature. However, at 10−2 s−1 and 10−1 s−1, the El increased with the rising of temperature. Scanning electron microscope (SEM) was used to investigate the microstructure of Ti6Al4V–5Cu alloy. The alloy grain boundaries (GBs) were found as continuous and discontinuous structural features, especially the high angle grain boundaries (HAGBs). The GB feature has contributed to the initiation of micro-cracks because of the creation of weakest regions in the material during deformation. The nature of GB geometry has also a tremendous contribution to the workability of Ti6Al4V–5Cu alloy at low forming temperatures. The presence of a high amount (%) LAGBs and the serrated nature of HAGBs structures determined the pull to grain pieces. The deformation mechanism of the Ti6Al4V–5Cu alloy at low forming temperatures was accomplished initially by boundary serration phenomenon due to strain-induced GB migration related to heat treatment at low strain condition, then by initiation of recrystallized grains-triggered by the plasticity behavior of strain induced sub-boundaries, and finally by the development of deformed grains generated by the reduction in corrugation propensity of GBs due to high strain condition.

Hot deformation behavior of FeCrCuMnNi high entropy alloy

The hot deformation behavior of FeCrCuMnNi high entropy alloy (HEA) was investigated using hot compression test within the temperature range of 500–970 °C at the strain rate of 0.1, 0.01, and 0.001 s−1 up to the strain of 0.6. An Arrhenius-type equation was used to evaluate the hot deformation behavior of the alloy and propose the constitutive equation. FeCrCuMnNi HEA revealed a typical hot deformation behavior with almost 250 kJ/mol deformation activation energy, which was mostly governed by the lattice diffusion of Cu. Discontinuous dynamic recrystallization (dDRX) was the main restoration phenomenon during hot deformation in which the grain boundary sliding and dislocation sliding were suggested as the main active mechanisms. The processing maps were plotted based on the efficiency of energy consumption (η) and flow instability (ξ). It was revealed that the instability region between 750 and 850 °C at different strain rates might be directly related to the formation of a hard sigma phase within this temperature range.

Development of temperature-speed modes of hot deformation of Co – 28Cr – 6Mo alloy based on processing maps

In the article, the tests of the medical alloy Co – 28Cr – 6Mo after homogenization for uniaxial compression at temperatures of 1000, 1100 and 1200 °C and strain rates of 1, 10, and 50 s­–1 were carried out using the Gleeble System 3800. The stress-strain curves describing the alloy deformation behavior were obtained. The calculations of hot deformation parameters (activation energy, Zener-Hollomon parameter) were performed using three models (power-law, exponential, and hyperbolic sine function) describing the flow stress. The highest degree of convergence was shown by the calculation results based on the power function and the hyperbolic sine function. These models can be used to accurately calculate the flow stress at given temperature and strain rate parameters, or to simulate the deformation process. Also, based on processing maps, the authors developed the deformation-speed modes of hot deformation of the Co – 28Cr – 6Mo alloy. It will make it possible to choose the optimal rolling modes in the future. According to the data obtained, favorable temperature-speed conditions for hot deformation are shifted as deformation accumulates to the region of high temperatures and low strain rates. At the same time, the extremely unfavorable zone with negative values of the ξ-criterion, which appears at e = 0.3 – 0.4, continues to grow quite significantly with an increase in the deformation effect. Hot deformation of the Co – 28Cr – 6Mo alloy at low compression ratios (e < 0.2) is more expedient to perform at temperatures above 1150 °C and strain rates of at least 20 s–1. With an increase in deformation degree, it is necessary to choose lower strain rates (1 – 5 s–1) and higher deformation temperature.

Deformation Behavior of AEREX350 Alloy during Bolt Hot Heading Processing

AEREX350 is a nickel-cobalt fastener superalloy developed for high temperature applications such as aerospace and petrochemical industries. The AEREX350 alloy has superior creep resistance and rupture properties similar to the other MP family alloys. As for AEREX350 alloy, scholars have carried out many studies on its cold working process, heat treatment process, stress relaxation performance and identification of precipitated phase [3-9], while very limited research on the hot deformation behavior of this interesting alloy during hot heading process. This paper is concentrated on the deformation behavior of the alloy during hot heading process.

Microstructural evolution and constitutive analysis of Al-Mg-Zn-Er-Zr based on arrhenius-type and machine-learning algorithm

In this work, artificial neural network (ANN) is employed to predict the hot deformation behavior of Al-Mg-Zn alloys containing small amounts of Er and Zr. A comparative study between the experimental results and the computational results based on Arrhenius constitutive equation and an ANN model was performed, where the theoretical calculation was used to predict the hot deformation behavior of the alloy. The results showed that relative errors obtained from Arrhenius constitutive equation were in the range of − 17.7% to + 13.6%, whereas the errors varied from − 9.3% to + 9.7% via ANN model. It suggests that the ANN model can avoid some uncertainties of the constitutive equation and predict the thermal deformation behavior of alloys more effectively. The dislocation density has also decreased with an increasing temperature or a decreasing strain rate. The dynamic aging effect and the dislocation density showed the opposite trend. As hot deformation can induce the intermittent precipitation of Mg32(Al, Zn)49 at the grain boundaries, it is expected to improve the corrosion performance of alloy materials.

Effect of high temperature deformation on the deformation behavior and thermodynamic properties of a Zr-based bulk amorphous alloy

Zr 55.7 Cu 22.4 Ni 7.2 Al 14.7 alloy rods with a diameter of 3 mm were prepared by copper mold suction casting. The structure, thermodynamic properties and plastic deformation behavior of the specimens before and after compression in supercooled liquid region were studied by X-ray diffractometer (XRD), differential scanning calorimeter (DSC) and uniaxial compression machine (equipped with a high-temperature oven). The range of thermal forming process parameters was also discussed. The results show that the alloys have obvious glass transition and crystallization kinetics, and the crystallization activation energies obtained by the Kissinger and Ozawa equations are 297.1 kJ/mol and 294.9 kJ/mol, respectively. The amorphous alloys exhibit stress overshoot in low temperature region at high strain rates and deformation behavior of alloy softening in high temperature region at medium to high strain rates. Meanwhile, the viscosity of the alloy remains approximately constant at 740 K and 750 K, showing Newtonian fluid characteristic. It can be concluded that the optimal thermoplastic forming process ranges from 740 K to 750 K, 5 × 10 −4 s −1 to 5 × 10 −3 s −1 . The crystallization activation energies of the specimens after deformation are slightly higher than before, and they increase with the increase of strain rate. • Zr-based bulk amorphous alloy has a good thermodynamic stability, which facilitates thermoplastic forming. • The amorphous alloy shows superplastic deformability at high temperatures and strain rates. • The crystallization activation energies of the deformed specimens are higher than that of the undeformed. • The crystallization activation energies of the alloys after deformation increase with increasing strain rate.

Mechanical Performance and Deformation Behavior of CoCrNi Medium-Entropy Alloy at the Atomic Scale

CoCrNi medium-entropy alloy has superior cryogenic properties with simultaneous growth of strength and plasticity at low temperatures. In order to observe the microstructure and deformation behavior of the alloy at the atomic scale, its mechanical properties and deformation mechanism at different temperatures and strain rates were investigated using molecular dynamics. It is indicated that the alloy’s strength was enhanced at low temperatures and high strain rates due to the production of high dislocation density. The introduction of grain boundaries significantly decreased the dislocation density during the alloy’s deformation and correspondingly reduced the crystal strength. However, the introduction of twin boundaries in polycrystalline grains obviously enhanced the strength of the polycrystal, especially at the twin boundary spacing of 3.08 nm. The strength’s enhancement was attributed to the increasing dislocation density produced by the interaction between twin boundaries and dislocations during deformation.

An investigation into Arrhenius type constitutive models to predict complex hot deformation behavior of TC4 alloy having bimodal microstructure

The purpose of this study was to determine the plastic deformation behavior of TC4 alloy having bimodal microstructure at hot forming conditions and establish a suitable constitutive model. The bimodal microstructure was obtained by plate die forging at 985 °C to a deformation of 40% and then annealing at 720 °C for 1 h followed by air cooling. Quasi-static tensile tests were performed at temperatures ranging from 750 to 900 °C and strain rates of 0.0001–0.1 s−1. The experimental stress-strain curves revealed that the alloy exhibited complex deformation behavior with considerable strain hardening, dynamic recovery, and continuous dynamic recrystallization. The processing map is established to delineate the safe and unsafe thermomechanical conditions for material hot forming that revealed the existence of superplasticity at 0.0001 s−1 and 750–900 °C, DRX at 0.001 s−1 and 800–900 °C, and flow instabilities at 0.1–0.01 s−1 and 800–850 °C. Modified Arrhenius type constitutive models with strain compensated using polynomial equation (PSCAM) and exponential equation (ESCAM) were established to predict the complex deformation behavior of the alloy. Also, a novel optimization method utilizing an evolutionary algorithm (EA) and generalized reduced gradient (GRG) was employed to establish an optimized polynomial strain compensated Arrhenius type constitutive model (OPSCAM). The predictability of the three established models is evaluated and compared during strain hardening and dynamic softening of the material. The correlation coefficients of ESCAM, PSCAM, and OPSCAM were 0.98, 0.99, and 0.99, respectively, showing a good correlation for the three models. Percentage average absolute relative error for the three models is 13.76%, 9.66%, and 9.14%, respectively, during strain hardening and 12.40%, 8.41%, and 6.78%, respectively, during dynamic softening. The study showed that OPSCAM could adequately predict the deformation behavior of TC4 alloy with bimodal microstructure during both hardening and softening regions and could be used to simulate the hot forming process.

Plastic deformation behavior and constitutive modeling of Cu-50Ta alloy during hot compression

This paper presents a study on plastic deformation behavior of Cu–50Ta alloy at temperatures of 286–473 K and strain-rate of 0.01–6200 s−1. The effects of temperature, strain-rate, and strain on the yield strength, flow stress, and strain-rate sensitivity coefficient were determined. A phenomenological model was established to predict variation of the strain-rate sensitivity coefficient for Cu–50Ta alloy under dynamic compression. A Johnson–Cook constitutive model was established to predict the equivalent stress–equivalent plastic strain relationship under extreme deformation (high temperature and strain-rate). The results showed that the plastic deformation behavior of Cu–50Ta alloy was affected by temperature, strain-rate, and strain. The material exhibited obvious strain-rate strengthening and thermal softening. As the strain-rate increased, the yield strength logarithmically increased. At a temperature of 286 K, the strain-rate increased from 0.01 s−1 to 6200 s−1, and the yield strength increased from 543.75 MPa to 881.13 MPa. In addition, the yield strength linearly decreased as the deformation temperature increased. Under conditions of dynamic deformation, the variation of strain-rate sensitivity coefficient could be expressed as a function of strain-rate and strain. The phenomenological model accurately described the variation of the strain-rate sensitivity coefficient of Cu–50Ta under dynamic deformation conditions. The Johnson–Cook constitutive parameters, calibrated by experimental data, described the plastic deformation behavior of the alloy under high-velocity impact.

Three-dimensional hot processing map of a nickel-based superalloy (Alloy 925) established by modified artificial neural network model

The hot deformation behavior of Alloy 925 in the temperature range of 900–1150 °C and strain rate range of 0.01–10s−1 was investigated through the isothermal hot compression tests. Based on the artificial neural network model, the stress distribution in the three-dimensional (3D) space consisted of deformation condition parameters was reconstructed. Afterwards, the 3D distribution maps of strain rate sensitivity (m) and power dissipation efficiency (η) were proposed to reveal the effect of deformation parameters on the hot workability. Furthermore, a novel 3D processing map was established by combining the traditional dynamic materials model and the corresponding data set. Through the microstructural characterization, it can be found that the instability regions exhibit inhomogeneous microstructure with massive distorted grains and few dynamic recrystallization (DRX) grains, while the stable regions are characterized by various DRX mechanisms, including discontinuous dynamic recrystallization, continuous dynamic recrystallization, and twin-DRX. Noteworthily, the relatively low η-value (<22%) was revealed in the high temperature-high strain rate domain caused by substantial occurrence of DRX. Finally, the optimum processing parameters at the true strain of 0.85 can be determined to be 970–1150 °C and 0.01–1.08s−1 with the η-value of 30.6–42.3%. In contrast, the construction method of novel 3D processing map can effectively avoid data distortion and also demonstrate a better validity for predicting hot workability. Through the present work, the feasibility of artificial neural network for learning complex hot deformation behavior has been illustrated. It not only has better prediction of typical microstructure, but also can reproduce the adiabatic heating law, which is convenient to be used in actual industrial production.

Constitutive modeling of the hot deformation behavior of CoCrFeMnNi high-entropy alloy

The unfolding characteristics of high-entropy alloys (HEAs) are challenging traditional materials science field with promise for innovative applications, including aerospace and defence. This makes them strong candidates for future applications in the aerospace and defense industries. This research focuses on the hot compressive behavior of equiatomic CoCrFeMnNi alloy at strain rates of 0.01 s−1 and 1 s−1 and temperatures ranging between 200 and 800 °C. The experimental results were used to develop plastic flow stress models for a variety of existing constitutive models, namely, the Johnson-Cook, modified Johnson-Cook, Zerilli-Armstrong, modified Zerilli-Armstrong, Zener-Hollomon, Hensel-Spittel, and modified Hensel-Spittel. The models were then compared using the correlation coefficient (R) and average absolute relative error (AARE) to determine their suitability for predicting the deformation behavior of this alloy. The results show that the modified Johnson-Cook, Zener-Hollomon, Hensel-Spittel, and modified Hensel-Spittel models are all found to provide reasonable predictive accuracy for the studied alloy. Microstructural analysis was also conducted to compare the samples' microstructures before and after deformation to confirm the occurrence of discontinuous dynamic recrystallization when strained at 800 °C. This phenomenon explains the material's stress behavior at a lower strain rate, which affects the modeling results.