Hot Deformation Behavior Research Articles

Hot deformation behavior and hot-metal-gas-forming process of V micro-alloyed high manganese steel

Hot deformation behavior and hot-metal-gas-forming process of V micro-alloyed high manganese steel

Fabrication and performance evaluation of CICC jacket based on modified N50 austenitic steel for CFETR magnet

The hot deformation behavior of modified N50 austenitic stainless steel in the temperature range 950∼1250 °C and strain rate range of 0.01–50/s was studied by uniaxial compression experiment. The processing map and the constitutive equation for the finite element simulation were established, and the recrystallization mechanism was discussed. The results indicated that the dominant deformation mode DDRX (discontinuous dynamic recrystallization) increased with the rise of deformation temperature while the CDRX (continuous dynamic recrystallization) was on the contrary. There is a decrease in global recrystallization with increasing strain rate, up to a threshold 1/s beyond which the global recrystallization began significantly promotion owing to not only the adiabatic heat and higher stored energy, but also quick Post-DRX mechanism induced by delay quenching. The reasonable hot working interval was determined by a hot working map, then the most suitable hot extrusion parameters (1180°C-100 mm/s) were further obtained with the help of finite element simulation, and ultimately, the industrial hot extrusion trials of N50 pipes with Post-DRX features were further completed. The tensile performance of final jacket pipes was far beyond the current mainstream low-temperature austenitic structural steel and met the requirements of the new generation of superconducting coil jacket materials.

Machine Learning Techniques in Predicting Hot Deformation Behavior of Metallic Materials

Machine Learning Techniques in Predicting Hot Deformation Behavior of Metallic Materials

Grain size and orientation affected deformation inhomogeneity and local damage of hot-deformed Al-Zn-Mg alloy

The forming defects at elevated temperature caused by the microstructural evolution such as grain size, crystal orientations are the critical issue that induced deformation inhomogeneity and local damage which severely limits the application of Al-Zn-Mg alloys in thin-walled structure manufacturing. In this study, the hot deformation behavior and microstructural evolution were investigated via hot stretching tests, electron backscatter diffraction (EBSD) and the transmission electron microscopy (TEM) characterization. Then, an integrated multiscale constitutive model coupled dislocation density based crystal plasticity (CP) model and phase field method (PFM) was established through the reconstructed configuration of deformation gradient emphasized on a damaged part. The coupled CP-PFM model was numerically implemented into Düsseldorf Advanced Material Simulation Kit (DAMASK) software. Subsequently, a set of virtual polycrystalline RVE models assigned with different average grain sizes and two types of RVE models with realistic crystal orientations were constructed from EBSD data. The experimental and simulation results of the Al-Zn-Mg alloy under hot tensile loading showed that the grain size refinement leads to the increase of grain boundary density, which leads to the rapid increase of dislocation density, uniform damage distribution and better work hardening ability. In addition, the coordination of the activation of different slip systems between adjacent grains will lead to the uneven distribution of dislocation density and local damage.

Study of the effect of dual-phase transformation on the processing map of Al0.9FeCoNiCr high-entropy alloys under peak stress conditions

ABSTRACT Single-pass thermal compression simulation experiments were performed on a dual-phase Al0.9FeCoNiCr high-entropy alloy at strain rates of 1–0.001 s−1, temperatures of 850–1050°C (true strain of 0.916). According to a model of the dynamic DMM processing map proposed by Prasad et al, the hot-deformation behaviour of the alloy was analysed. The flow-instability regions were obtained as follows: temperature 850–1040°C with a strain rate 1–0.1 s−1 and 850–900°C with a strain rate of 1–0.001 s−1. The microstructure was obtained by EBSD characterisation. It was found that under certain strain-rate conditions, the FCC phase in the dual-phase Al0.9FeCoNiCr high-entropy alloy did not change significantly at low temperatures but increased significantly when the temperature was over 1000°C. The hot-working properties of the alloy are affected when the FCC phase exceeds 80%.

Investigation of the Hot Deformation Behavior and Mechanism of a Medium-Entropy CoCr0.4NiSi0.3 Alloy

The CoCrNi-based medium-entropy alloys (MEA) have been extensively investigated due to their exceptional mechanical properties at both room and cryogenic temperatures. To investigate the hot deformation behavior and the recrystallization mechanism of the CoCr0.4NiSi0.3 medium-entropy alloy, a series of deformation tests was conducted using the MMS-100 thermal simulation tester, with deformation conditions of 0.001–1 s−1/850–1150 °C. During the hot deformation process, the flow stress initially increases up to its peak value before gradually decreasing towards a steady state level. Higher flow stress levels are observed with increasing strain rate and decreasing deformation temperature. The estimated activation energy for hot deformation of this alloy is approximately 423.6602 kJ/mol. The Arrhenius-type constitutive equation is utilized to establish a modified model while incorporating power dissipation theory and the instability criterion of a dynamic material model to construct power dissipation maps and instability maps. By superimposing these maps, hot processing maps with strains of 0.4, 0.5, and 0.7 are derived. In this investigation, it is observed that regions of instability exclusively occur when the true strain exceeds 0.4. These regions of instability on the hot processing map align well with experimental findings. The suitable range of parameters for hot-working decreases as the true strain increases. The microstructure was analyzed using electron backscatter diffraction and transmission electron microscopy (TEM) techniques. The volume fraction of dynamic recrystallization (DRX) decreases with increasing strain rate but diminishes with rising temperature. The TEM characterization elucidated the mechanism of DRX in this MEA. The presence of the long-period stacking ordered (LPSO) phase was observed in both the face-centered cubic matrix and hexagonal close-packed recrystallized grains under different deformation conditions. The LPSO phase originates from the matrix at a low strain rate, whereas it is generated during recrystallization at a high strain rate. The observed increase in flow stress of the as-cast MEA is primarily attributed to the synergistic effects arising from the interaction of the dislocation with twins and the second phase. The onset of instability is effectively suppressed within a limited range through the formation of coherent second phases such as L12, LPSO, and superlattice structures resulting from phase transitions. These second phases serve as nucleation sites for recrystallization and contribute to the strengthening of dispersion. Furthermore, their interaction with dislocations and twins significantly influences both flow stress behavior and recrystallization kinetics under hot deformation. These findings not only deepen our understanding of the underlying deformation mechanisms governing MEA but also offer valuable insights for designing CoCrNi-based alloys with improved mechanical properties at elevated temperatures.

Hot Deformation Behavior and Microstructural Evolution of the As-rolled 7050Al Alloy

The hot deformation behavior of the as-rolled 7050 aluminum alloy was investigated using isothermal hot compression experiments with temperatures ranging from 300 to 460 °C and strain rates ranging from 0.001 to 1 s−1, up to a total strain of 1.1. A strain-compensated Arrhenius (SCA) model was established based on the experimental flow stress data. The predictive accuracy of the model was numerically evaluated using the Correlation Coefficients (R) and the Average Absolute Relative Error (AARE). Electron backscatter diffraction (EBSD) was used to characterize the effects of strain rate and compressive temperature on the microstructure evolution and recrystallization behavior. The results indicated that the geometric dynamic recrystallization (GDRX) occurred at high strain rates or low temperatures, while continuous dynamic recrystallization (CDRX) became the dominant recrystallization mechanism with increasing deformation temperature and decreasing strain rate. The work hardening effect was enhanced during the later stage of deformation, and discontinuous dynamic recrystallization (DDRX) became the main recrystallization mechanism.

Hot deformation behavior, superplasticity and microstructure evolution of a new hot isostatic pressed nickel-based superalloy

The new hot isostatically pressed (HIP) superalloy has demonstrated remarkable superplastic characteristics, as evidenced by studying the compression and tensile deformation behavior. To identify the superplastic deformation zone, the instability regions at various strain variables were overlaid onto the strain rate sensitivity index (m) distribution map at a strain of 0.6, resulting in the acquisition of a new hot working map. The tensile test results showed that under the conditions of 1080 °C-10−2.5 s−1 (0.35 < m < 0.43) and 1030 °C-10−3 s−1 (0.66 < m < 0.74) which located in the superplastic deformation zone in the new hot working map, the new HIPed superalloy exhibited superplasticity, and the elongation was 395 % and 410 %, respectively. Considering the hot working map and the microstructure evolution, the suitable hot working window was further optimized to be 1030–1080 °C and 0.001–0.005 s−1. At high strain rate and low temperature conditions, continuous dynamic recrystallization (CDRX) was the primary mechanism for dynamic recrystallization (DRX), while with the gradual decrease of strain rate, discontinuous dynamic recrystallization (DDRX) tended to occur and dominate the process. DDRX dominated under high temperature deformation condition.

Hot deformation behavior of Ni50.4Ti34.6Hf15 high-temperature shape memory alloy

Due to their extreme requirements, conventional Ni–Ti shape memory alloys (SMAs) are no longer suitable for aerospace applications. Adding Hf to Ni–Ti SMAs can significantly enhance their suitability for aerospace applications, particularly in high-temperature environments. In this regard, the hot/thermal deformation behavior of Ni50.4Ti34.6Hf15 high-temperature shape memory alloys (HTSMAs) was systematically investigated by using a Gleeble-3800 thermocompression simulation machine. The results prove that the Ni50.4Ti34.6Hf15 alloys have more strain sensitivity than the temperature during the hot/thermal deformation process. In detail, the flow stress increases with the increase in strain rate and decreases with the increase in deformation temperature. From the microstructure evolution point of view, the recovery effect will increase with the increase in deformation temperature, and the recrystallization effect will increase with the increase in strain rate. Following the obtained stress-strain curves, the flow behavior of Ni50.4Ti34.6Hf15 alloys during hot/thermal deformation was established. A modified constitutive equations model was proposed using careful consideration of deformation temperature and strain rate. It was found that the calculated strain activation energy was 363.945 kJ/mol in the range of 700∼800 °C and 512.489 kJ/mol in the range of 900∼1000 °C. Based on the constitutive equation, the calculated values were consistent with the experimental values, which indicated reliable analysis with high prediction accuracy. Furthermore, the thermal processing maps under different conditions were constructed, and it was determined that the optimum hot/thermal deformation processing parameters of Ni50.4Ti34.6Hf15 alloys were 940∼1000 °C and 0.01–0.04 s−1.

Constitutive Modeling for Flow Stress and Processing Maps of a 0.2C–2.0Mn–0.5Cr Microalloyed Steel

Low‐carbon microalloyed steel with the microstructure of bainite is frequently utilized to produce automotive parts. The systematic investigation of the hot deformation behavior can serve as a reference for the optimization of deformation process parameters. The hot deformation of 0.2C–2.0Mn–0.5Cr microalloyed steel is studied. Based on the stress–strain curve, an Arrhenius model with strain compensation is established. The correlation coefficient R2 and the average absolute relative error calculated according to this model are 0.962 and 4.871%. The microstructure evolution at the strain of 0.90 is studied. In the stable region with substantial power dissipation, the microstructure is uniformly fine. The strain rate is high in the stable region with low‐power dissipation, and the room‐temperature microstructure after deformation retains a large amount of deformation storage energy and fine substructures. During deformation, the banded structures are formed in the instable region. The difference in dislocation density between the band structure and the nearby regions promotes the formation of necklace microstructures. Therefore, the 0.2C–2.0Mn–0.5Cr microalloyed steel has an ideal deformation process window in the range of a hot deformation temperature of 880–920 °C and a strain rate of 0.1–0.3 s−1.

Application of Ni-based superalloy in aero turbine blade: A review

A superalloy is a high-performance alloy used for achieving stability and strength at elevated temperatures. Generally, a temperature of about 800°C is developed at the first stage of the aero turbine blade. So it is a challenge to choose a material that can withstand such high temperatures. Nowadays advanced generation single crystal Ni-based superalloys are being used for the fulfillment of high-temperature requirements in aero turbine components. But the continuous effort is being carried out to manufacture new materials that can withstand more and more temperatures generated at aero turbine because the high-temperature operation of the turbine is directly proportional to the efficiency of a turbine engine. The requirement of high-temperature application upgraded the Ni-based superalloy and different generations of alloys were prepared from time to time those were discussed in the paper. Recent developments of superalloys in the paper mainly include fifth and sixth generations of superalloys those incorporate Hf, Re, and Ru-like elements in significant amounts. A brief extension discussion has been placed on the types, processing, and hot deformation characteristics of Ni-based superalloys. VIM melting, single crystal growth, directional solidification, and powder metallurgy techniques for manufacturing Ni-based superalloys are discussed in detail. The strengthening mechanism and machinability behavior depict the characteristics of superalloys in a mechanical direction. Heat treatment and hot deformation behavior of Ni-based superalloy was precisely discussed in the context so as to correlate the strength of the material with the temperature change. Overall, the paper describes the origin, processing and characteristics of Nickel based superalloy in detail.

Discontinous and continuous dynamic recrystallization of Fe-12.5Cr–4Al–2Mo-0.03Nb-0.08Y alloy during hot deformation

The hot deformation behavior and microstructure of Fe-12.5Cr–4Al–2Mo-0.03Nb-0.08Y alloy were studied under conditions of 800 °C–1200 °C/0.01 s−1∼10 s−1 using a combination of hot compression experiments, EBSD and TEM characterization. The results indicate that the deformation temperature and strain rate have a significant impact on the flow stress and microstructure of the alloy, especially the deformation temperature. The constitutive equation constructed in this paper can reflect the hot deformation process and accurately calculate flow stress value of the FeCrAl alloy in corresponding states. The FeCrAl alloy undergoes DRV and DRX during hot deformation. DDRX grains distributed along the original grain boundaries mainly formed at low deformation temperatures and high strain rates, while CDRX grains mainly formed at high deformation temperatures and low strain rates and characterized by the internal distribution of the original grains. Moreover, the orientation of DDRX grains is mostly different from that of adjacent original grains, while the orientation of CDRX grains is relatively close to that of the original grains.

Effect of temperature on superplastic deformation behavior of 2198 Al–Cu–Li alloy

Al–Li alloy possesses remarkable advantages such as low density, high specific strength and specific elastic modulus, making it an exceptional aerospace structural material with considerable application potential. However, Al–Li alloy suffers from poor formability, which restricts its broader engineering applications. Alternatively, superplastic forming at high temperatures is widely applied for producing such components. Temperature is a key factor affecting the thermal deformation properties of Al–Li alloy. In this study, tensile tests of 2198 Al–Cu–Li alloy were conducted at different temperatures, and dedicated characterizations were performed to reveal the underlying mechanisms responsible for the hot deformation behavior. Results reveal that three distinct stages are observed in the superplastic deformation process of this alloy. Specifically, in the initial low-temperature range (400 °C–450 °C), incomplete dynamic recrystallization (DRX), accompanied by grain rotation and elongation plays a dominant role in the hot deformation mechanism. In the middle temperature stage (450 °C–500 °C), both DRX and grain boundary sliding (GBS) occur. At the high-temperature stage (500 °C–550 °C), diffusion creep emerges as the prominent mechanism. Moreover, optimum superplasticity is achieved at 500 °C, which results from a synergistic combination of several factors, including grain refinement by DRX, an increased fraction of high-angle grain boundaries (HAGBs), reduced dislocation density and weak texture.

Microstructure Evolution and Constitutive Modelling of Deformation Behavior for Al-Mg-Si-Cu-Sc-Zr Alloy Processed with Isothermal Multidirectional Forging

This research is devoted to the microstructure evolution and deformation behavior of the Al-1.2Mg-0.7Si-1.0Cu-0.1Sc-0.2Zr alloy during the isothermal multidirectional forging (MDF) in a large cumulative strain and temperature range. The structure investigation of the studied alloy revealed several phases precipitated during solidification, among which θ(Al2Cu), Q(Al5Cu2Mg8Si6), Mg2Si, Sc-bearing W(AlScCu) and V(AlSi2Sc2) phases were observed. The MDF at 150–350 °C and a maximum cumulative strain of 14.4 significantly refined grain structure providing a mean grain size of 1.2–2.1 µm. The L12 structured Al3(Sc,Zr) dispersoids with a mean size of 10 ± 1 nm were formed during two-step homogenization annealing. Due to Zener pinning of the nanoscale dispersoids and fine-grained structure, the alloy exhibited near-superplastic behavior in a temperature range of 460–500 °C and strain rate range of 2 × 10−3–1 × 10−2 s−1 with the maximum elongation to failure of ~300%. After a strengthening heat treatment, the forged alloy exhibited the yield strength of 326 ± 5 MPa, ultimate tensile strength of 366 ± 5 MPa, and elongation of 10 ± 3%. The hot deformation behavior was described using the Arrhenius type model. The developed model demonstrated high predictability accuracy with a maximum average absolute relative error of 6.6%.

Study on thermal deformation constitutive model of NiCoFeAlCrMo high-entropy alloy with FCC / L12 coherent structure

Due to its multi-principal component characteristics, high-entropy alloys exhibit excellent comprehensive mechanical properties and become a new generation of engineering structure alternative materials. At present, a single constitutive model is used to describe the change of flow stress in the study of hot deformation behavior of high-entropy alloys, and there are some problems such as inaccurate prediction accuracy or inapplicability of the model in some hot processing intervals. In this paper, three different constitutive models are combined to fully consider the applicability of the model in different temperature ranges, and the change of flow stress behavior is accurately described, which is of great significance for subsequent deformation mechanism research, hot processing process optimization, numerical simulation and so on. Thermal compression experiments on cast Ni28.5Co18.6Fe18.2Al16.3Cr10.5Mo4 Ti2.3Nb0.6W0.9C0.2 high-entropy alloy were carried out using a Gleeble-3800 thermal simulation tester with deformation temperatures in the range from 900 ℃ to 1150 ℃ and strain rates from 0.001 s−1 to 1 s−1. The constitutive relationships between true stress and strain, temperature and strain rate were established, while the heat deformation process of this alloy under different deformation conditions by Arrhennius, Modified Johnson-Cook and Modified Fields-Backofen models were characterized. The results indicate that Arrenius model describe the rheological behavior of the alloy better in a wider temperature range and at a wider strain rate range. Comparatively, the model shows the highest prediction accuracy in the high-temperature region and slightly lower accuracy in the mesothermal and low-temperature regions. The modified J-C and F-B models have better prediction accuracy in the low-temperature and medium-temperature regions, respectively. Due to the different deformation conditions, dislocation configurations such as dislocation tangles, dislocation networks, and subcrystalline junctions can be observed in the plastic deformation region. The dislocation density of this alloy increases with increasing strain rate and decreasing deformation temperature after deformation.

Hot deformation behavior of novel high-strength Mg-0.6Mn-0.5Al-0.5Zn-0.4Ca alloy

Hot deformation behavior of novel high-strength Mg-0.6Mn-0.5Al-0.5Zn-0.4Ca alloy

Constitutive model for hot deformation behaviors of Al/Cu bimetal composites based on their components

The hot deformation behavior of Al/Cu bimetal composites was investigated using isothermal compression tests at temperatures of 400–500 °C and strain rates of 0.001–0.1 s−1 by considering the effects of volume fractions of composite components (30%–51% Al). In this regard, new proper constitutive equations were developed using Arrhenius-type and the rule of mixture (ROM) models. Experimental flow stress (FS) showed that processing parameters and volume fraction affect the flow behavior of composite as the volume fraction of copper has a more substantial impact on the flow behavior of the composite rods at elevated temperatures. The values of correlation coefficient (r) and average relative error of the developed Arrhenius-type constitutive equation and ROM model were 0.9826, 0.9742 and 0.9718, and also 0.18%, 1.69% and –0.84% for volume fractions of 51%, 42% and 30% Al, respectively. The results indicate that the newly developed constitutive model can successfully predict the hot working behavior of the considered bimetal composite. Finally, the microstructure of composites was investigated under different processing conditions. The dominant mechanisms for three considered volume fractions were identified at different temperatures, strains, and strain rates specified for the hot deformation of the Al/Cu composite.

Phase transformation and deformation behavior under isothermal compression in β-quenched metastable Ti-10V-2Fe-3Al alloy

Comprehensive knowledge on the hot deformation behavior and microstructure evolution of metastable titanium alloys is critical for process optimization and microstructure regulation. The isothermal compression of β-quenched metastable titanium alloys (Ti-10 V-2Fe-3Al) was experimented at different temperatures (600 ℃−800 ℃) with the strain rate of 10−3 s−1 in present work. The stress-strain curves show that the flow stress reduces with increasing temperature, and the characteristics of the stress-strain curve at low temperature (600 ℃) are clearly distinct from those at other high temperatures. During the isothermal compression process at 600 °C, the deformation went through four stages: initial linear hardening (stage Ⅰ), Discontinuous yielding phenomenon (DYP, stage Ⅱ) followed by work hardening (stage Ⅲ) and final flow softening (stage Ⅳ). Further observations of the microstructure throughout each deformation stage revealed that the precipitation of αGB and the proliferation of dislocation lead to initial linear hardening behavior. The softening of deformation behavior during the discontinuous yield stage is originated from the fragmentation of αGB and the generation of a large amount of moving dislocations. Almost all β phase transformed into lamellar α phase as the deformation degree increased, which is the main cause of work hardening after discontinuous yield. The major causes of final flow softening are the formation of deformation bands and spheroidization of α phase. The present work analyses the correlation between the deformation behavior and microstructure features on the deformation mechanisms of metastable β titanium alloys and reveals the potential mechanism of metastable β alloy under thermal deformation and provides more comprehensive information for the optimization of the process parameters of hot deformation.

Hot Deformation Behavior and Mechanisms of SiC Particle Reinforced Al-Zn-Mg-Cu Alloy Matrix Composites

A systematic and comprehensive analysis of the hot deformation and mechanisms of SiC particle-reinforced aluminum matrix composites is significant for optimizing the processing of the composites and obtaining the desired components. Based on this, related research on 11 vol% SiCp particle-reinforced 7050Al matrix composites was carried out. Hot compression experiments were carried out on the Gleeble-3500 thermal simulator to study the hot deformation behavior of composites at the temperature of 370–520 °C and strain rate of 0.001–10 s−1. The hyperbolic sine constitutive equation of the material was established, and the processing map was calculated. Combining the typical metallograph and misorientation angle distribution, the microstructure evolution mechanism of composites was analyzed, and the effect of particles on recrystallization behavior was investigated. Under certain process conditions, the dominant deformation mechanism of composites changed from dynamic recovery (DRV) to dynamic recrystallization (DRX), and the grain boundary sliding mechanism began to play a role. In addition, high temperature tensile and elongation at break were tested, and it was found that the dominant form of fracture failure changed from brittle fracture of the particles to ductile fracture of the matrix as the temperature increased.

The high-temperature deformation and microstructural evolution mechanism of Mg-Gd-Y-Zn-Zr alloy formed by CMT arc additive forming

ABSTRACT The hot deformation behavior of the Mg-Gd-Y-Zn-Zr alloy formed by CMT arc additive under 400°C, 0.1 s−1, and 50% deformation were systematically studied by means of hot compression test, constitutive equation, numerical simulation and microscopic structure. After deformation, twinning appeared in the microstructure. A large number of high-density dislocations and stacking faults were distributed around it. This was the thermal stress generated during the compression process, causing the deformation of the grains and stress concentration within the grains. The deformation at the center of the specimen was severe, the grains were elongated, and the equivalent stress was high. The simulated peak stress was close to the experimental value. The effect of the high-temperature deformation on the crystal slip was independent of the deformation region. The slip occurred along the {10-10} crystal plane and the <11-20> crystal direction with the deformation, which was related to the Hcp structure of the alloy.