Hot Compressive Deformation Behavior Research Articles

Study on hot compressive deformation behavior and microstructure evolution of G13Cr4Mo4Ni4V steel

To solve the problem of poor uniformity of microstructure of high alloy bearing steel G13Cr4Mo4Ni4V after rolling, the deformation behavior of the steel and its effect on the microstructure evolution was studied systematically. Gleeble-3800 thermo-mechanical simulator was used for precise control of deformation temperature ranging from 1000 to 1200 °C and deformation rate 0.01–10 s−1. Based on modified stress and strain curves by temperature and friction, the processing map of tested steel was drawn. Electron backscatter diffraction (EBSD) and transmission electron microscope (TEM) were used to analyze the typical microstructure and carbide properties of different hot working domains respectively. The results showed the processing map could be divided into four regions: domain A 1000–1150 °C, 0.1–10 s−1; B 1000–1100 °C, 0.01–0.1 s−1; C 1100–1150 °C, 0.01–0.1 s−1 and D 1150–1200 °C, 1–10 s−1. Domain A was characterized by incomplete dynamic recrystallization (DRX) which included fine recrystallized grains and elongated deformed grains, whose softening mechanism was mainly discontinuous DRX (dDRX) and limited DRV and continuous DRX (cDRV) related to the ferrites and carbides. For domain B, the deformed grains gradually disappear with temperature rising, instead serrated grains appear with dDRX as dominating softening mechanism. A large number of carbides hinder DRX at 1000 °C with low temperature. With the increase of temperature, carbides dissolve and DRX degree increases. Grain coarsening is obvious because of high deformation temperature and low strain rate in domain C, although the nanoscale MC type carbides prevent recrystallization grain coarsening to some extent. Completely DRX resulted in uniform and fine with defect-free deformation microstructure in domain D, whose volume fraction of recrystallization reached up to 0.96 according to EBSD results. By considering the uniformity of microstructure and the distribution of carbide comprehensively, domain D is an ideal region for hot working.

Hot compressive deformation behavior and microstructural evolution of the spray-formed 1420 Al–Li alloy

The 1420 Al–Li alloy has been widely used in the aerospace field. To investigate the hot workability of the alloy, a series of hot compression tests were carried out on the spray-formed alloy in the temperature range of 300°C–450 °C with strain rates of 0.0001s−1-10s−1. First, an improved Johnson-Cook model was developed by considering the coupling effect of strain, strain rate, and temperature, and the prediction error of the model was reduced to 5.3 %. Subsequently, processing maps with various strains were established. In addition, the microstructural evolution under various deformation conditions was systematically studied using the electron backscatter diffraction (EBSD) technique. The alloy exhibited uniform deformation under the synergistic effect of the continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX) mechanisms. Finally, the feasible hot working windows were identified as 425°C–450°C and 0.01s−1-0.1s−1 based on processing maps and microstructural evolution results. This work could offer comprehensive guidance for the hot working process of 1420 Al–Li alloy from both the macro and the micro aspects.

Effect of N on hot deformation behavior of high-Mn austenitic steel

The present study dealt with the hot compression deformation behavior of Fe−18.5Mn–7Cr−0.6C and Fe−18.5Mn–7Cr−0.6C−0.21 N high-Mn austenitic steels within a temperature range of 900–1200 °C, a strain rate range of 0.01–5 s−1, and a true strain of 0.7. The accurate constitutive equations were established according to their flow curves, and the deformation microstructures were also analyzed. The results revealed that the dominant softening mechanism for the two test steels without substantial peak stress (higher Zenger-Holloman parameter values) could also be dynamic recrystallization (DRX) rather than dynamic recovery (DRV). The addition of N enhanced the strain rate sensitivity of high-Mn austenitic steel at low temperatures and high strain rates. Furthermore, the addition of N increased the high temperature strength and hot deformation activation energy (Q) of high-Mn austenitic steel. Moreover, the addition of N could also increase the DRX volume fraction and refine the DRX grain size of high-Mn austenitic steel.

Hot compressive deformation behavior of Ti-8Al-1Mo-1 V titanium alloy at elevated temperatures: Focus on flow behavior, constitutive modeling, and processing maps

The deformation behavior of the near-α Ti-8Al-1Mo-1 V titanium (Ti-811) alloy was studied by isothermal compression tests in the temperature range of 950–1075 °C and strain rates of 0.001–1 s−1. According to the physical properties of titanium alloys, the effects of adiabatic heat and friction during hot deformation process were modified on the stress-strain curves, especially at low temperatures and high strain rates. The results showed that the flow stress increases with increasing the strain rate and decreases with an increase in process temperature. Hyperbolic sine (sinh) and Cingara equations were used to model the flow behavior of Ti-811 alloy at elevated temperatures. Results showed a suitable fitting among the calculation and experimental results by the sinh equation at low strain rates (0.001 and 0.01 s−1) and by the Cingara equation at high strain rates (0.1 and 1 s−1). The activation energy values (Q) of Ti-811 alloy in two-phase and single-phase regions were calculated as 738 and 194 kJ/mol.K, respectively. The processing maps showed that in the single-phase region, the instability domain was located at 1025 °C and 1050 °C and high strain rates (0.1 and 1 s−1) and low strain rates (0.001 and 0.01 s−1) were considered as stability domain. For the α + β region, an instability domain was only observed at 1000 °C and 0.01 s−1. Microstructural observations showed occurring dynamic recrystallization, dynamic phase transformation, and globularization of alpha phase in stability domain.

Deformation behavior and microstructure evolution induced by nano-sized Al6Mn phase particles in a homogenized Al–6Mg–0.8Mn alloy during hot compression

In the present work, hot compression deformation behavior and microstructure evolution in a homogenized Al–6Mg–0.8Mn alloy with nano-sized Al6Mn phase particles were investigated at the temperature ranging from 300 to 500 °C with tha strain rate of 0.001–1 s−1. The constitutive equation of the Al–6Mg–0.8Mn alloy was established and the average deformation activation energy was calculated to be 167.07 kJ/mol. The flow stress of the alloy decreased with increasing the compression temperature and raised with increasing the strain rate, which was closely associated with the competitive relationship between work hardening and dynamic recovery (DRV). The low compression temperature accelerated the formation of shear bands in the alloy. The low strain rate was beneficial for the generation of low-angle grain boundaries (LAGBs), and the high compression temperature and strain rate promoted dynamic recrystallization (DRX). The interaction between the nano-sized Al6Mn phase particles participating near the initial grain boundaries and mobile dislocations facilitated the generation of LAGBs. Discontinuous DRX through grain boundary bulging mechanisms and continuous DRX with the LAGBs transforming to HAGBs led to the preferred formation of recrystallized grains along the initial large-sized grains. Furthermore, this interaction also resulted in the dissolution of Al6Mn phase particles.

Hot compression deformation behavior and dynamic recrystallization of a precipitate-free Mg–Bi–Sn alloy

The addition of Sn improves the properties of Mg–Bi-based alloys, and can potentially overcome the high-temperature limitations of magnesium (Mg) alloys. However, high-Sn alloying leads to stress concentration during hot extrusion. Hence, in this study, the dynamic recrystallization (DRX) mechanism and hot-deformation behavior of a novel precipitate-free Mg–0.25Bi–0.25Sn alloy during hot compression conducted at 250–400 °C with strain rate of 0.001–1 s−1 were examined in detail by constructing processing maps and deriving constitutive equation. The obtained correlation coefficient was 0.99113, indicating that the proposed method can adequately predict the hot deformation behavior of the studied alloy. The calculated average activation energy was 143.0336 kJ/mol. According to the processing maps, the ideal processing areas corresponded to the conditions of 300–400 °C/0.001 s−1/1 s−1 and 400 °C/0.1 s−1. In addition, a transformation of prismatic <a> slip to pyramidal II <c+a> slip was observed at 350 °C, and the continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX) processes occurred during hot compression. The classification of the dominant DRX mechanisms was based on the Zener–Hollomon parameter (Z). Under high-Z deformation conditions, CDRX and DDRX occurred simultaneously; however, CDRX was the predominant process. Under medium-Z deformation conditions, DDRX was the only DRX process. Under low-Z deformation conditions, DDRX dominated over the DRX mechanism and was partially accompanied by CDRX.

Effects of molybdenum on hot deformation behavior and microstructural evolution of Fe40Mn40Co10Cr10C0.5 high entropy alloys

ABSTRACT The remarkable properties of high-entropy alloys (HEAs) have resulted in their increased research interest and prompted the use of various strategies to enhance their mechanical properties. In this study, the effects of Mo on the hot compressive deformation behavior of carbon-containing FeMn40Co10Cr10 HEAs in the temperature range of 800–1000°C and strain rate of 0.001–0.1 s−1 was investigated. The microstructural evolutilon and phase structure were characterized by X-ray diffraction and electron backscattered diffraction. The effects of strain, strain rate, and deformation temperature on the thermally activated deformation restoration process of the Fe39.5Mn40Co10Cr10C0.5 and Fe38.3Mn40Co10Cr10C0.5Mo1.7 HEAs during hot compression were represented by the Zener–Hollomon parameter. Dynamic recrystallization was initiated at 800°C with the strain rate of 0.001–0.1 s−1. The precipitation of the M23C6 carbide along the grain boundaries and within the matrix exerted a strong pinning effect on the grain/subgrain boundaries and promoted dynamic recrystallization through the particle-stimulated nucleation of recrystallization. Moreover, the addition of Mo to the Fe39.5Mn40Co10Cr10C0.5 HEA changed the dynamic recrystallization mechanism by reducing the stacking fault energy and enhancing the reverse f c c ↔ h c p phase transformation. The heterogeneous microstructure composed of ultrafine, fine, and larger grains in the Fe38.3Mn40Co10Cr10C0.5Mo1.7 HEA could be obtained by the nucleation of new recrystallized grains at large deformed grain boundaries adjacent to the first necklace structures and shear bands.

Experimental and Numerical Studies on Hot Compressive Deformation Behavior of a Cu-Ni-Sn-Mn-Zn Alloy.

Cu-9Ni-6Sn alloys have received widespread attention due to their good mechanical properties and resistance to stress relaxation in the electronic and electrical industries. The hot compression deformation behaviors of the Cu-9Ni-6Sn-0.3Mn-0.2Zn alloy were investigated using the Gleeble-3500 thermal simulator at a temperature range of 700-900 °C and a strain rate range of 0.001-1 s-1. The microstructural evolution of the Cu-9Ni-6Sn alloy during hot compression was studied by means of an optical microscope and a scanning electron microscope. The constitutive equation of hot compression of the alloy was constructed by peak flow stress, and the corresponding 3D hot processing maps were plotted. The results showed that the peak flow stress decreased with the increase in the compression temperature and the decrease in the strain rate. The hot deformation activation energy was calculated as 243.67 kJ/mol by the Arrhenius equation, and the optimum deformation parameters for the alloy were 740-760 °C and 840-900 °C with a strain rate of 0.001~0.01 s-1. According to Deform-3D finite element simulation results, the distribution of the equivalent strain field in the hot deformation samples was inhomogeneous. The alloy was more sensitive to the deformation rate than to the temperature. The simulation results can provide a guideline for the optimization of the microstructure and hot deformation parameters of the Cu-9Ni-6Sn-0.3Mn-0.2Zn alloy.

The hot compressive deformation behavior of cast Mg-Gd-Y-Zn-Zr alloys with and without LPSO phase in their initial microstructures

Samples of Mg-8.2Gd-3.8Y-1.1Zn-0.4Zr alloy with and without an intragranular lamellae-shaped long period stacking ordered (LPSO) phase were prepared through heat treatment and a series of hot compression tests on these materials were conducted to examine and evaluate the influence of LPSO on the hot compressive deformation behavior and deformation mechanisms at a given alloy composition. The values of activation energy for plastic flow (Q c ) of the solution treated (without LPSO phase) and annealed alloys (with intragranular LPSO phase) were larger than that for pure Mg, indicating that the presence of a high amount of rare earth (RE) elements and LPSO in the Mg matrix significantly increases Q c . The Q c value of the annealed alloy was larger than that of the solution treated alloy at all the strain levels (223.3 vs. 195.5 kJ/mol in average) and the largest difference in Q c between the two alloys was recorded at the smallest strain of 0.1 where precipitation of LPSO during deformation was limited in the solution treated alloy. These observations imply that the formation of LPSO phase out of the RE-rich solid solution matrix during deformation increases Q c , but the increment is not so large. Analysis of the hot compressive data of the alloys with LPSO phase and the alloys with RE-rich solid solution matrix in literatures indicates the similarity of the effect of the LPSO and RE-rich solid solution matrix phases on Q c and high-temperature strength.

Hot Compression Deformation Behavior and Microstructure of As-Cast and Homogenized AA2195 Al-Li Alloy

To understand the effect of the initial state of AA2195 Al-Li alloy on the forming process, as-cast and homogenized ingots were compressed by using a Gleeble-3150 thermo-mechanical simulator at different temperatures (360–480 °C) and strain rates (0.01–10 s−1). The hot compression deformation behaviors and microstructural characteristics of the two types of ingots were systematically investigated. The as-cast alloy possessed a better hot compressibility with higher power dissipation efficiency and lower rheological stress than the homogenized alloy under the same deformation conditions. When the temperature was increased above 450 °C, all the alloys showed similar rheological curves. Based on the rheological stress curves, processing maps for the as-cast (AC) and homogenized (HG) alloys were established, and optimal processing domains were identified. In addition, the homogenized alloys were dominated by a fibrous microstructure during deformation, whereas the as-cast alloy produced fine crystals at low temperature (360 °C) and equiaxed crystals at high temperature (480 °C). Our results show that it is possible to use the as-cast 2195 Al-Li alloy as the initial billet to get complicated components. This is attributed to the dispersed eutectic phases, which can provide more nucleation sites for Dynamic Recrystallization (DRX) and Dynamic Recovery (DRV) during hot deformation.

Optimized hot working parameters of Fe2.5Ni2.5CrAl multi-principal element alloys

The hot compressive deformation behavior of Co-free Fe2.5Ni2.5CrAl multi-principal element alloys (MPEAs) was investigated in the temperature and strain rate ranges of 800–1100∘C and 0.001 s−1 and 1 s−1, respectively. Microstructural observations were carried out by optical microscopy (OM) and electron backscatter diffraction (EBSD). A constitutive model based flow-stress analysis was carried out, the activation energy (Q) was obtained as 315.9 kJ/mol at steady state. The strain rate sensitivity (m), the power dissipation (η), and instability parameter (ξ) were utilized to construct the processing maps. Power-law breakdown and unstable flow occurred at the high strain rates at which strain hardening was pronounced. The optimal condition for successful hot working was determined to be at strain rates in the range of 10−2–10−3 s−1 and a temperature range of 850 ~ 1020∘C. FEM simulations revealed the strain and stress distribution during hot deformation and predicted instabilities during hot forming. The main deformation mechanism was dislocation climb with a stress exponent n > 5. The Q value for plastic flow in the power-law creep regime was calculated considering the effect of lattice diffusion of atoms and was in accordance with the measured Q value. Thus, our study revealed the hot working characteristics and the optimum processing parameters for successful hot working of Fe2.5Ni2.5CrAl MPEAs.

Hot compression deformation behavior and processing maps of Al–0.5Mg–0.4Si–0.1Cu alloy

To improve the hot working stability of Al–0.5Mg–0.4Si–0.1Cu alloy, isothermal compression tests were performed at the temperature range of 350–500 °C and strain rate of 0.001–10 s−1. Strain-compensated Arrhenius constitutive equation containing Zener–Hollomon parameters was established to describe the hot deformation behavior. Its accuracy was evaluated within the whole strain range and the established constitutive equation can well predict the flow behavior. In addition, intrinsic machinability was further analyzed by constructing processing maps under different true strains based on dynamic material models. Microstructures are in fine agreement with processing maps and flow instability occurred mainly in high strain rate regions due to the presence of adiabatic shear bands and flow localization. Dynamic softening mechanism of the alloy mainly stems from dynamic recovery and partial dynamic recrystallization. Based on processing maps and microstructure observations, optimal process parameters of alloy were obtained, which are beneficial to optimize its hot working parameters.

Hot compression deformation behavior and constitutive model of 2050 Al-Li alloy

Isothermal compression experiments of 2050 AL-Li alloy were carried out by Gleeble-3800 thermal-mechanical simulator. Hot compression deformation behavior of the alloy under the conditions of deformation temperature of 300~500 °C and strain rate of 0.01~10 s-1 was studied. The constitutive model of thermal deformation was established. Results indicate that there is an obvious rheological steady state in the isothermal compression process of 2050 aluminum alloy. The microstructure shows that the alloy has recrystallization. 2050 aluminum alloy is a positive strain rate sensitive material. At constant temperature, the steady state flow stress increases with the increase of strain rate. Arrhenius constitutive model can accurately predict the rheological behavior of 2050 aluminum alloy. The average absolute relative error (AARE) of the relative error between the experimental value and the predicted value is 8.59%.

Hot compressive deformation behaviour and constitutive equations of Mg–Pb–Al–1B–0.4Sc alloy

ABSTRACT The hot compression features and microstructural evolution of Mg–Pb–Al–1B–0.4Sc alloy deformed at the strain rate range of 0.001–1 s−1 and the temperature range of 493–613 K were investigated by isothermal compression tests. The results show that the flow stress is significantly influenced by deformation conditions. The true stress decreases with the raised temperature or the reduced strain rate. The Zuzin-type model and Arrhenius-type constitutive model were employed to predict the flow behaviour of Mg–Pb–Al–1B–0.4Sc alloy. The values of and in the Arrhenius-type model are 6.353% and 9.595, respectively, which are smaller than the 13.653% and 24.662 of the Zuzin-type model, indicating that the Arrhenius-type model is more suitable for predicting the flow stress of this alloy. The processing maps and microstructure show that the optimum strain rates and temperatures are 0.001–0.015 s−1 and 550–613 K, respectively.

Research on Hot Deformation Behavior of Mo‐Containing Ti2AlNb‐Based Alloy

Herein, the hot compression deformation behavior and microstructure instability of the different Mo‐containing Ti2AlNb‐based alloys are investigated in the temperature range of 900−1150 °C and strain rate range of 0.001−1 s−1. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) are used to characterize the microstructure evolution during the deformation process. The results reveal that Mo element addition can refine the lamellar α2/O phase of Ti2AlNb‐based alloy. In addition, it has a certain influence on the phase‐transition temperature of the alloy, which leads to the narrowing of the O + B2 + α2 phase region. During the hot compression process, the spheroidization of the lamellar structure in Ti2AlNb−0.5Mo alloy is mainly through the transformation of O→B2 + α2, whereas the microstructure of Ti2AlNb−2Mo alloy is mainly converted from the O phase to the B2 phase. In addition, it is found that the high content of Mo element causes the segregation of Al element and leads to poor plasticity and stability of the Ti2AlNb−2Mo alloy. As such, the hot deformation performance of the Ti2AlNb−0.5Mo alloy is significantly better, which provides theoretical guidance for the composition design of the Ti2AlNb‐based alloy.

Hot Compression Deformation Behavior of Spray-Formed AlSn20Cu Alloy

The hot deformation behavior of spray-formed AlSn20Cu alloy during hot compression deformation was studied, and the constitutive equation of AlSn20Cu alloy was established. The samples of spray-formed AlSn20Cu alloy were compressed on Gleeble-3500 thermal simulation test machine. The error of the true stress caused by adiabatic heating effect in the experiment was corrected. The constitutive equation of spray-formed AlSn20Cu alloy could be represented by Zener-Hollomon parameter in a hyperbolic sine function. The results showed that the deformation temperatures and strain rates had a notable effect on the true stress of the alloy. At the identical deformation temperature, the true stress increased with the increase of strain rate. When the strain rate was constant, the stress decreased with the increase of deformation temperature. After hot compression deformation, the tin phase was elongated along the direction perpendicular to the compression axis with short strips and blocks. With the increase of deformation temperature and the decrease of strain rate, Sn phase distribution became more homogeneous.

Hot deformation behavior and processing map of a Sn0.5CoCrFeMnNi high entropy alloy with dual phases

The hot compressive deformation behavior of a cast Sn0.5CoCrFeMnNi high-entropy alloy composed of dual phases, an FCC solid solution phase and a MnNiSn-rich ordered FCC phase (with a volume fraction of 30%), was investigated in temperature and strain rate ranges of 1023–1248 K and 10-3–10 s−1, respectively. During hot deformation, the MnNiSn-rich phase with a relatively low melting temperature (1297 K) underwent a significantly higher degree of dynamic recrystallization (DRX) than the FCC solid solution phase. Continuous DRX occurred in the FCC solid solution phase, but it was pronounced only at the highest temperature of 1248 K. The Sn0.5CoCrFeMnNi alloy exhibited dislocation climb creep at low strain rates and high temperatures and power-law breakdown at high strain rates and low temperatures. The flow stresses of Sn0.5CoCrFeMnNi were notably lower than those of CoCrFeMnNi, though they shared similar deformation mechanisms, by a factor of 0.37–0.71, and this could be explained by the rule of the mixture model considering the contribution of the FCC solid solution phase and the MnNiSn-rich phase to the total deformation rate under the isostress condition. Compared to the Al element in Al0.5CoCrFeMnNi, the Sn element is anticipated to create a larger atomic size misfit in Sn0.5CoCrFeMnNi but promote less viscous glide (solute drag) creep·. The analysis for explaining this reason was conducted from the perspective of factors that affect solute drag creep and breakaway stresses of dislocations from the solute atmosphere.

Insight into the Role and Mechanism of Nano MgO on the Hot Compressive Deformation Behavior of Mg-Zn-Ca Alloys

Aiming to investigate the role and mechanism of nano MgO on the hot compressive deformation behavior of Mg alloys, the Mg-3Zn-0.2Ca alloy (MZC, in wt%) and the 0.2MgO/Mg-3Zn-0.2Ca alloy (MZCM, in wt%) were investigated systematically in the temperature range of 523–673 K and the strain rate range of 0.001–1 s−1. MZCM shows finer grains and second phase because of the refinement effects of added MgO. Flow behavior analysis shows that the addition of nano MgO promotes the dynamic recrystallization (DRX) of MZC. The flow stress of MZCM is lower than that of MZC during deformation at 523–623 K but exhibits a reverse trend at 673 K and 0.1–1 s−1. The constitutive analysis indicates that dislocation climb is the dominant deformation mechanism for MZC and MZCM. The addition of nano MgO particles decreases the stress sensitivity and deformation resistance for thermal deformation and improves the plasticity of the MZC. Besides, according to the processing map constructed at strains of 0.7 and corresponding microstructure evolution, MZCM exhibits higher power dissipation efficiency and smaller instability regions than MZC, and the optimum hot working condition for MZCM was determined to be at 623–653 K and 0.01–0.001 s−1.

Microstructure evolution and hot deformation behavior of Cu−3Ti−0.1Zr alloy with ultra-high strength

Abstract The hot compression deformation behavior of Cu–3Ti–0.1Zr alloy with the ultra-high strength and good electrical conductivity was investigated on a Gleeble–3500 thermal-mechanical simulator at temperatures from 700 to 850 °C with the strain rates between 0.001 and 1 s−1. The results show that work hardening, dynamic recovery and dynamic recrystallization occur in the alloy during hot deformation. The hot compression constitutive equation at a true strain of 0.8 is constructed and the apparent activation energy of hot compression deformation Q is about 319.56 kJ/mol. The theoretic flow stress calculated by the constructed constitutive equation is consistent with the experimental result, and the hot processing maps are established based on the dynamic material model. The optimal hot deformation temperature range is between 775 and 850 °C and the strain rate range is between 0.001 and 0.01 s−1.

A comparative study of phenomenological, physically-based and artificial neural network models to predict the Hot flow behavior of API 5CT-L80 steel

The hot compressive deformation behavior of as-cast 5CT-L80 medium-carbon steel was investigated under the different elevated temperatures range from 1173 K to 1373 K and diverse strain rate range from 0.001 s−1 to 1 s−1. The multi-peak flow stress curves were observed during deformation, indicating a complex behavior of this steel due to metallurgical phenomena like dynamic recrystallization. Therefore, the modified Johnson-Cook (J-C) as a phenomenological model, modified Zerilli-Armstrong (Z-A) as a physically-based model, and feed-forward back propagation artificial neural network (BP-ANN) model were purposed to describe the high-temperature flow behavior of the studied material. So, the predictability of the developed models is compared by the standard statistical parameters. The extraordinary and accurate performance was observed in the BP-ANN model to predict the complexities of the compressive behavior of 5CT-L80 steel, whereas the modified J–C model has more precise than the modified Z-A model.