Hot Deformation Behavior Research Articles

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.

Microstructural and Thermal Characterization of AZ31 and Ca-modified AZ31 Magnesium Alloys: Insight into Dynamic Recrystallization and Discontinuous Precipitation Phenomena

Magnesium alloys are highly desirable for weight critical applications owing to their high weight to strangth ratio. However, their poor formability at room temperature limits their widespread use in industrial applications. In this study, we invstigate the hot deformation behaviour of AZ31 and AZ31-0.7% Ca magnesium alloys and explore their microstructural and thermal properties. Our findings reveal that dynamic recrystallization during hot deformation leads to successful grain refinement in the AZ31 alloy, resulting in a normal grain size distribution. In contrast, the AZ31-0.7% Ca alloy shows bimodal grain size distribution due to the addition of calcium. Additionally, the number and size of β-Mg17Al12 particles were found to increase with the addition of a small amount of calcium. These particles are responsible for the discontinuous precipitation phenomenon, which strongly influences microstructural changes during hot rolling. Our study provides valuable insights into the dynamic recrystallization and discontinuous precipitation phenomena of magnesium alloys, which can aid in the development of novel alloys with improved formability and mechanical properties.

Constitutive description, processing maps, and un-explored deformation mechanisms of pure Mg and Mg-6Al(wt%) alloy under hot compression

This study investigates the hot deformation behavior and final microstructure features with and without aluminum (Al) incorporation in magnesium (Mg). To this end, pure Mg and Mg-6Al(wt%) alloy were subjected to high-temperature compression and systematically analyzed the flow stress, activation energies, Zener Hollomon parameters, processing maps, and microstructure evolution, including geometrically necessary dislocations under different g vectors. These all were in an excellent relationship with each other. The microstructure analysis greatly validated the processing map parameters. Amazingly, we have attained an unexplored grain boundary sliding phenomenon under high-strain rate compression in pure Mg. This phenomenon is only reported in high-temperature tensile specimens, especially for those who attained superplasticity. Unfortunately, the mechanism attained at a strain rate (10 s−1) and temperature (573 K), which is referred to as an unstable region. Above the temperatures of 573 K, the Mg lost thermal stability, and an abrupt increase in grain size happened (3–40 µm). The addition of Al restricted the abnormal grain growth at elevated temperatures and retained grain size within < 10 µm. The higher geometrically necessary dislocation density and increase in grain boundary energy are the potential reasons for the thermal stability of Mg-Al alloy. Therefore, incorporating the Al not only enhances the formability of Mg but also provides many different stable zones, thermal stability and increases the power dissipation efficiency.

Constitutive Modeling and Microstructural Investigations for Evaluating Hot Deformation Behavior of Additively Manufactured Inconel 718 Superalloy

Constitutive Modeling and Microstructural Investigations for Evaluating Hot Deformation Behavior of Additively Manufactured Inconel 718 Superalloy

Deformation Behavior and Processing Map of AlCoCrFeNiTi0.5 High-Entropy Alloy at High Temperature

AlCoCrFeNiTi0.5 high-entropy alloy (HEA) shows excellent properties in hardness and corrosion resistance. AlCoCrFeNiTi0.5 HEA was prepared using a non-consumable vacuum arc furnace. Hot-deformation behavior of AlCoCrFeNiTi0.5 HEA was explored under 1073–1373 K with a strain rate between 0.001 and 1 s−1 using a Gleeble-3800 thermomechanical simulator. The constitutive equation was established using the Arrhenius model, and the deformation activation energy and material constant were obtained. The processing map of HEA within 0.3–0.6 deformation was drawn according to dynamic material model (DMM). The results show that the hot-deformation process of HEA is dominated by work hardening combined with dynamic recovery, and dynamic recrystallization. The flow stress of HEA is significantly affected by deformation temperature and strain rate. The constitutive equation was constructed and verified, and the correlation coefficient of R2 = 0.9873 indicated that the constitutive equation can be used to accurately predict the flow stress of HEA. The processing map of HEA shows that the optimal hot-working process parameters are in the range of temperature 1150–1300 K and strain rate 0.002–0.05 s−1. This work will provide theoretical guidance for the hot-processing of HEA, which effectively promotes the application of the HEA in industry.

Simulation and Experimental Study of Hot Deformation Behavior in Near β Phase Region for TC21 Alloy with a Forged Structure

Quasi-beta processing was considered to be a promising processing method to obtain a component with excellent mechanical properties. To achieve an optimized quasi-beta processing parameter for TC21 alloys, the hot deformation behavior in the near β phase region for the alloy with a forged structure was investigated by the thermal compression test and finite element (FEM) simulation. The obtained results indicated that the flow behavior of the samples was significantly influenced by the hot deformation parameters, and it exhibited a flow hardening behavior at the start stage of deformation. Based on the experimental data, the constitutive equation and processing maps were obtained. The optimum hot processing parameter was 986 °C/10−3 s−1. Based on the FEM simulation results, the evolution of the temperature field, strain field, and stress field in the deformed samples at different strains exhibited a similar trend in the unstable region, which was distributed symmetrically along the center line of the samples, with the center area of the samples being the highest and the center area of the section being the lowest.

Hot deformation behavior and microstructure evolution model of 7055 aluminum alloy

Hot compression tests were conducted on 7055 aluminum alloy under different strain rates, temperatures, and reduction ratios. The influence of deformation parameters on microstructure evolution and hot deformation behavior was studied through EBSD and TEM characterization. An Arrhenius constitutive model was established and the recovery and recrystallization characteristics of the alloy under different conditions were analyzed. Results showed that the softening mechanism during the hot compression process of 7055 aluminum alloy was mainly attributed to recovery and partial recrystallization. The Zener-Holloman (Z) parameter was utilized to reveal the combined effects of strain rate and temperature on recrystallization behavior. Under conditions of high LnZ values (20 < LnZ), the alloy exhibited predominantly discontinuous dynamic recrystallization (DDRX) characteristics, while at low LnZ values (14 < LnZ <17), it displayed significant continuous dynamic recrystallization (CDRX) characteristics. The alloy showed a coexistence of CDRX and DDRX phenomena under conditions of moderate LnZ values (17<LnZ <20). In addition, based on the characterization, statistical analysis, and examination of the hot-compressed microstructure of the 7055 aluminum alloy, models for recrystallization fraction, grain size evolution, and deformed grain size were established, and an average grain size model was further developed. Comparison between the finite element simulation results based on the models and experimental results demonstrated good agreement in predicting the average grain size.

Effects of cooling rate in homogenization on microstructure, hot deformation resistance and subsequent age-hardening behavior of an Al–Mg–Si alloy

In this paper, the microstructure evolution in an Al–Mg–Si alloy during the soaking and cooling of homogenization was investigated. Moreover, the effects of the cooling rate on the hot deformation and subsequent age-hardening behavior were studied. During the soaking, the eutectic Mg2Si is dissolved, the solute segregation is eliminated, and the Fe-bearing phase is refined. During subsequent cooling, no precipitate is formed in the water-quenched sample, while β'' and β-Mg2Si are the predominant phases formed in the air- and furnace-quenched samples, respectively. The experiments agree with the simulated continuous cooling transformation (CCT) curves. The cooling rate in homogenization has a significant effect on the flow stress when the compression is performed at 450 °C. The air-quenched sample exhibits the highest flow stress due to the formation of nanoscale β-Mg2Si particles. The effect of the cooling rate diminishes as the compression temperature increases. At a compression temperature of 500 °C, the water-quenched sample exhibits a slightly higher flow stress due to the precipitation of micrometer-scale β-Mg2Si particles and the Mg and Si solutes retained in the matrix. The compressed samples have nearly similar thermal effects and peak aging hardness increments after compression at 500 °C, indicating that the age-hardening potential of the alloys is equivalent. The same types of precipitates are formed in all compressed samples at peak aging, including the GP zone, β'', β′ and B′, where β'' is the main strengthening phase. The relationship between the precipitation behavior and the increments of hardness, electrical conductivity (EC) was analyzed.

Hot deformation and microstructural evolution of ultrasonically fabricated as-cast Al-7.3Zn-2.2Mg-2Cu alloy

Al-7.3Zn-2.2 Mg-2Cu alloy is known for its high strength, achieved because of higher alloying concentration. However, the higher alloying concentration presents challenges during the hot deformation process. Nevertheless, hot deformation proves to be an effective method for optimizing the microstructural and mechanical properties of the material. The research presented in the study focuses on investigating the hot working response of an ultrasonically fabricated age-hardening as-cast Al-7.3Zn-2.2 Mg-2Cu alloy. The objective is to observe the attainment of a uniform and dendrite-free microstructure after a single-step hot compression. The flow stress of the deformed specimens showed a notable increase as the temperature and deformation time decreased. This increase in stress was influenced by various factors, including deformation variables and precipitate size. The accurate prediction of the hot deformation behaviour was achieved by combining the constitutive equations and a workability map. The 3-dimensional workability map revealed a gradually increasing power dissipation efficiency (PDE) from 40% to 50% with increasing strain. At the end of 50% compression, four specific optimum working regions (PDE > 40%) were identified. Through detailed microstructural analysis, the best region for hot forging of ultrasonically mixed as-cast alloy for chemical homogeneity and upgraded property is obtained in the range of (350–450 °C) & (0.1–0.001 s−1). The highest extent of recrystallization (73%) was exhibited after deformation at 450 °C-0.001 s−1. The mechanism of dynamic softening during deformation is observed due to DRV, CDRX, and PSN. The microstructural response in 0.1–0.001 s−1 and 350–450 °C indicated dynamic recrystallization, whereas strained and non-working zone was observed at low deformation temperatures (≤350 °C).

Understanding hot deformation behavior and microstructural evolution in a novel Fe50(CoCrMnNi)50 medium entropy alloy

This study investigates the hot deformation behavior and microstructural evolution of a novel medium entropy alloy subjected to low strain rates and temperatures ranging from 650 °C to 850 °C. The alloy was subjected to hot compression testing under various conditions to observe its response. At all deformation condition, discontinous dynamic recrystallization was the main restoratory mechanism. After full recrystallization, grain sizes ranged from 1 to 5 μm, accompanied by an average hardness of 250 HV. The flow curves demonstrated a typical three-stage work hardening behavior across all deformation conditions, indicative of dynamic recrystallization. It is found that the deformation activation energy (Q) exhibited a negative slope with increasing strain, with an average value of Q = 267.7 kJ/mol. Zener-Hollomon parameter was determined from the experimental results and effectively used to simulate deformation, demonstrating good agreement with experimental findings. Remarkably, following the initial cycle of recrystallization, the deformation process shifted towards grain boundary sliding instead of secondary recrystallization, displaying characteristics reminiscent of superplastic behavior. Further analysis revealed a high strain rate sensitivity (m > 0.3) at 750 °C and 850 °C, with grain sizes lower than anticipated values. In summary, this study provides a comprehensive understanding of the hot deformation behavior and microstructural evolution in the Fe50-(CoCrMnNi)50 alloy. The findings shed light on dynamic recrystallization, deformation activation energy, and the unexpected shift to grain boundary sliding. These insights are valuable for advancing the knowledge of medium entropy alloys and their potential applications in various industries.

Constitutive Modeling of Hot Deformation Behaviors and Processing Maps of Mg–4.83Gd–2.36Nd–0.21Zr Alloy

Accurately assessing the hot workability and flow behavior is crucial in the preparation of high‐performance wrought Mg–rare earth (RE) alloys. The hot deformation behaviors and workability of Mg–4.83Gd–2.36Nd–0.21Zr alloy are examined via Gleeble 3500 thermosimulation tests across a range of deformation temperatures from 350 °C to 450 °C and strain rates ranging from 0.001 to 1 s−1. The experimental results reveal that the flow stress of the experimental alloy decreases as the temperature increases and the strain rate decreases. The activation energies for deformation (Q) of the experiment alloy are calculated by the hyperbolic constitutive equation and range from 186.78 to 234.97 kJ mol−1. Strain compensation is incorporated in constitutive modeling, resulting in the correlation coefficient (R) of 0.9865 and the average absolute relative error (AARE) of 5.4639%. Further, the processing maps are constructed at different strains based on dynamic material models, from which the feasible processing window of the experimental alloy is determined in the areas of deformation temperatures of 425–450 °C and strain rates of 0.01–0.1 s−1.

Mechanical behaviour and microstructural evolution of Ti–6Al–1Mo–1V–2Zr–2Cr–1Fe alloy subjected to hot compression deformation

A new titanium alloy with chemical composition of Ti–6Al–1Mo–1V–2Zr–2Cr–1Fe (wt.%) is designed and produced. The hot deformation behavior, microstructural evolution and texture evolution of the alloy after solution treatment are investigated in this paper. Firstly, the constitutive equation of solution-treated Ti–6Al–1Mo–1V–2Zr–2Cr–1Fe alloy with the consideration of strain compensation is obtained based on compressive test at the temperatures of 950–1100 °C and the strain rates of 0.01–10 s−1, which can be used to describe the flow behaviour at elevated temperatures. According to the corresponding constitutive equation, the flow stress of solution-treated alloy is accurately predicted, which is further verified by the experimental data. Furthermore, discontinuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX) are observed in the microstructures of the deformed alloys, where deformation temperature and strain rate have a significant effect on DDRX and CDRX processes of solution-treated Ti–6Al–1Mo–1V–2Zr–2Cr–1Fe alloy. Moreover, plastic deformation and dynamic recrystallization have a comprehensive influence on the texture evolution of solution-treated Ti–6Al–1Mo–1V–2Zr–2Cr–1Fe alloy. ηbcc-fiber textures of {100}<001> and {110}<001>, εbcc-fiber texture of {112}<111> and ξbcc-fiber texture of {110}<112> are the main texture compositions of the deformed samples, where all of the deformed samples exhibit a strong {100}<001> texture.

Dynamic Recrystallization Behavior of Q370qE Bridge Steel

Bridge steel has been widely used in recent years for its excellent performance. Understanding the high-temperature Dynamic Recrystallization (DRX) behavior of high-performance bridge steel plays an important role in guiding the thermomechanical processing process. In the present study, the hot deformation behavior of Q370qE bridge steel was investigated by hot compression tests conducted on a Gleeble 3800-GTC thermal-mechanical physical simulation system at temperatures ranging from 900 ℃ to 1100 ℃ and strain rates ranging from 0.01 s−1 to 10 s−1. The obtained results were used to plot the true stress-strain and work-hardening rate curves of the experimental steel, with the latter curves used to determine the critical strains for the initiation of DRX. The Zener-Hollomon equation was subsequently applied to establish the correspondence between temperature and strain rate during the high-temperature plastic deformation of bridge steel. In terms of the DRX volume fraction solution, a new method for establishing DRX volume fraction was proposed based on two theoretical models. The good weathering and corrosion resistance of bridge steel lead to difficulties in microstructure etching. To solve this, the MTEX technology was used to further develop EBSD data to characterize the original microstructure of Q370qE bridge steel. This paper lays the theoretical foundation for studying the DRX behavior of Q370qE bridge steel.

Revealing the hot deformation behavior of AZ42 Mg alloy by using 3D hot processing map based on a novel NGO-ANN model

The hot deformation behavior of AZ42 alloy was observed using thermal compression tests at a temperature scope of 250–400 °C and strain rate scope of 0.001–1 s−1. True stress-strain curves exhibited a combination of work hardening and dynamic softening features. A Northern Goshawk algorithm (NGO)-optimized artificial neural network (ANN) model was proposed. The established NGO-ANN model demonstrated impressive prediction accuracy, achieving a high determination coefficient of 0.991, a mean absolute percentage error of 3.51 %, and a root mean square error of 2.73. Subsequently, three-dimensional (3D) hot processing map based on the dynamic material model (DMM) theory was created. There were three different regions within the processing maps: the flow instability region (region A: 250–260 °C, 0.02–1 s−1, and region B: 300–400 °C, 0.01–0.1 s−1), high-power dissipation coefficient region (region C: 350–400 °C, 0.001–0.02 s−1, and region D: 300–350 °C, 0.5–1 s−1), and low power dissipation efficiency safety region (region E: the rest ones). Microstructural analysis revealed significant local plastic flow features in the flow instability region and a combination of coarse initial deformation grains and fine dynamic recrystallization (DRX) grains in the low power dissipation efficiency safety region. Fine and uniform grains were observed in the high-power dissipation efficiency region with DRX degree VDRX as high as 85.6 %, resulting in the best mechanical properties. Based on the established 3D hot processing map, the optimal process domains were determined.

Correction: Hot Deformation Behavior and Dynamic Recrystallization of a Medium Carbon Cr–Mo Steel for Class 16.8 Bolts

Correction: Hot Deformation Behavior and Dynamic Recrystallization of a Medium Carbon Cr–Mo Steel for Class 16.8 Bolts

Hot deformation behavior and mechanism of cold deformed CoCrCu1.2FeNi high entropy alloy

The high temperature deformation behavior and mechanisms of the cold-deformed CoCrCu1.2FeNi high-entropy alloy (HEA) were investigated by optical microscope (OM), scanning electron microscope (SEM) and electron backscattered diffraction (EBSD) at temperatures and strain rates of 950–1100 °C and 0.001–1 s−1, respectively. The results show that the flow stress increases as the deformation temperature decreases and the strain rate increases, and there is significant dynamic recrystallization (DRX) during the deformation process. 1050–1090 °C/0.02–1 s−1 and 975–1050 °C/0.002–0.2 s−1 are the optional hot temperature deformation regions. Discontinuous dynamic recrystallization (DDRX) occurs at different temperatures when the strain rate is 0.001 s−1 with a maximum recrystallization percentage of 90.28 %. The DRX degree gradually increases as the temperature rises from 950 °C to 1000 °C and from 1050 °C to 1100 °C. The maximum polar density of texture sharply increases to 11.78 at 1050 °C. The deformed microstructure leads to an increase in dislocation density, which could be effectively reduced by DRX.

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.

Constitutive equation and microstructure evolution of TiAl alloy during hot deformation

The hot deformation behavior of TiAl alloy is analyzed by combining the true stress–strain curve and microstructure analysis. The results show that the flow stress of TiAl alloy presents the characteristics of work hardening-dynamic softening, it increases with the increase of strain rate and decreases with the increase of temperature. Based on the true stress–strain curves, the flow stress of TiAl alloy under different deformation conditions is predicted by hyperbolic sinusoidal formula. In addition, the effects of deformation temperature and strain rate on the microstructure evolution of TiAl alloy are revealed. In the process of hot compression deformation, dynamic recrystallization and γ→α, β→α phase transformation occurs. During tensile deformation, TiAl alloy exhibits super-plasticity, which is mainly due to grain rotation and coordinated deformation of β phase.

Investigation on hot deformation behavior and quenching precipitation mechanism of 2195 Al-Li alloy

Al-Li alloys suffer from a narrow processing window. The hot deformation behavior of the ramp heating homogenized 2195 Al-Li alloy was investigated by hot compression test in the temperature range of 300–500 °C and strain rate range of 0.01–10 s−1, and the strain compensated Arrhenius constitutive relationship model and processing map of the alloy were established. The laws of Zener-Hollomon parameters on the age-hardening response and quenching sensitivity of the deformed alloy were analyzed. The quenching precipitation mechanism of the deformed alloy were revealed. The results showed that the hardness of the aged alloy tends to increase first and then decrease with increasing Z parameter, while the quenching sensitivity tends to decrease first and then increase. The quench-induced phases are precipitated under the induction of incoherent Al3Zr dispersoids within recrystallized grains. The boundary angle would affect the quenching precipitation behavior. It was also found that the types and amounts of second phases are significantly different between the homogenized and hot-deformed samples under slow cooling rate. The ramp heating homogenized 2195 Al-Li alloy after hot deformation at temperatures of 455–500 °C and strain rates below 1 s−1 possesses a lower flow stress, higher age-hardening response and smaller quenching sensitivity.

Constitutive Equation and Hot Deformation Behavior of SLM-GH3536 Alloy

Constitutive Equation and Hot Deformation Behavior of SLM-GH3536 Alloy