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In recent years, much attention has been devoted to understanding the pathways of phase transition between two equilibrium condensed phases (such as liquids and solids). However, the microscopic pathways of transition involving non-equilibrium, non-diffusive amorphous (glassy) phases still remain poorly understood. In this work, we have employed computer simulations, persistence homology (a tool rooted in topological data analysis), and machine learning to probe the microscopic pathway of pressure-induced non-equilibrium transition between the low- and high-density amorphous (LDA and HDA, respectively) ice phases of the TIP4P/2005 and ST2 water models. Using persistence homology and machine learning, we introduced a new order parameter that unambiguously identifies the LDA- and HDA-like local environments. The LDA phase transitions continuously and collectively into the corresponding HDA phase via a pre-ordered intermediate phase during the isothermal compression. The local order parameter susceptibilities show a maximum near the transition pressure (P*)—suggesting maximum structural heterogeneities near P*. The HDA-like clusters are structurally ramified and spatially delocalized inside the LDA phase near the transition pressure. We also found manifestations of the first-order low-density to high-density liquid transition in the sharpness of the order parameter change during the LDA to HDA transition. We further investigated the (geometrical) structures and topologies of the LDA and HDA ices formed via different protocols and also studied the dependence of the (microscopic) pathway of phase transition on the protocol followed to prepare the initial LDA phase. Finally, the method adopted here to study the phase transition pathways is not restricted to the system under consideration and provides a robust way of probing phase transition pathways involving any two condensed phases at both equilibrium and out-of-equilibrium conditions. [ABSTRACT FROM AUTHOR]

The high-pressure and high-temperature structural, mechanical, and dinamical stability of rhodium has been investigated via synchrotron X-ray diffraction using a resistively heated diamond anvil cell and density functional theory. The isothermal compression data have been fitted with a Rydberg-Vinet equation of state (EoS) with best-fitting parameters V 0 =55.046(16) Å 3 , K 0 = 251(3) GPa, and K 0 ′ = 5.7(2). The thermal equation of state has been determined based upon the data collected following four different isotherms and has been fitted to a Holland and Powell thermal equation-of-state model with α 0 = 3.36(7)x10 - 5 K - 1 . The measured equation of state and structural parameters have been compared to the results of ab initio simulations. The agreement between theory and experiments is generally quite good. The present results solve controversies between previous studies which reported values of the bulk modulus from 240 to 300 GPa. [ABSTRACT FROM AUTHOR]

Triple-layer stainless-steel clad plate having 317L stainless steel (SS317L) as cladding layer and ASTM SA516 GR60 (GR60) as backing layer was successfully fabricated through vacuum hot roll bonding (VHRB) at 1373 K (1100 °C) temperature and strain rate regime of 1–5 s−1, which were identified through process efficiency maps of the base materials (SS317L and GR60). The process efficiency maps were constructed by conducting isothermal compression tests within the temperature range of 1173 K (900 °C)–1473 K (1200 °C) and 0.1–50 s−1strain rate regime. Effect of post-rolling heat treatments on the mechanical properties of clad plate was studied after solutionization at 1173 K (900 °C) for 1 h followed by cooling at different rates, i.e., water quenching, air cooling, and furnace cooling. As compared to other post-rolling heat treatments, the ultimate tensile strength, uniform plastic elongation, and maximum shear strength showed a significant change from 524 MPa, 0.46 and 519 MPa to 652 MPa, 0.36 and 410 MPa, when the normalized clad plate was solutionized at 1173 K (900 °C) and water quenched. A drastic change in shear fracture mode from gradual failure in normalized condition to catastrophic failure was also noticed after water quenching. These changes are essentially manifestation of the microstructural change in GR60 layer which led to the change in mechanical properties. [ABSTRACT FROM AUTHOR]

Al–Ti–C/7075 aluminum matrix composites (referred to as 7075-ATC) containing uniformly distributed TiC particles and traces of TiAl3 particles were produced by introducing 2 wt. % Al–Ti–C master alloy through stir casting. Isothermal thermal compression behavior at 300 °C–450 °C and 0.001 s−1 to 1 s−1 strain rates was studied in a Gleeble-3800 thermal simulation tester. Peak stress is influenced by deformation temperature and strain rate, reaching its maximum at low temperatures and high strain rates. The activation energy of the final thermal deformation is 150.11 kJ/mol, attributed to particle reinforcement. A sinusoidal hyperbolic Eigen structure equation for composites considering strain compensation is developed to describe the rheological stresses in composites. Dynamic recrystallization at 450 °C and a strain rate of 0.001 s⁻1 enhances composite molding properties. After hot compression, composites exhibit higher activation energy (Q) than cast 7075 and in situ particle-reinforced 7075 due to the obstruction of dislocations by the particles, grain refinement, and pinning effect on the grains. Based on the experimental results, an intrinsic model considering strain compensation was developed to accurately predict the thermal deformation behavior. EBSD results indicated that dynamic softening primarily occurred through dynamic restitution and partial recrystallization. The efficiency of softening peaked at 39% under a strain of 0.6, deformation temperatures between 350 °C and 450 °C, and strain rates ranging from 0.0009 s⁻1 to 0.0111 s⁻1. [ABSTRACT FROM AUTHOR]

Magnesium alloys with a high volume fraction of secondary phases exhibit inferior formability. Therefore, investigating their thermal deformation characteristics is critical for optimizing thermal processing techniques. In this work, isothermal compression experiments were performed on a Mg-15Gd-8Y-6Al-0.3Mn alloy with an elastic modulus of 51.3 GPa with a substantial volume of aluminum-rare earth (Al2RE) phases. The rheological behavior and microstructural evolution of the material were systematically investigated at varying temperatures (350–500 °C) and strain rates (0.001–1.000 s−1). The calculated thermal processing diagram indicates that the unstable region gradually enlarges with increased strain, and all unstable regions appear within the high-strain-rate, low-temperature domain. The ideal thermal processing range of the alloy is 350–500 °C at strain rates ranging from 0.001 to 0.016 s−1. Particle-stimulated nucleation and discontinuous dynamic recrystallization are both verified to be responsible for the recrystallized microstructure of the alloy. The recrystallized grains exhibit a relatively random crystallographic orientation. As recrystallization proceeds, the texture gradually transitions from a typical [0001] texture in the compression direction to a random texture accompanied by decreased texture intensity. This work sheds new light on the thermo-mechanical processing of high-modulus Mg alloys, which could help design suitable processing techniques for related materials. [ABSTRACT FROM AUTHOR]

A novel Al-Cu-Ni composite, featuring Ni-Al3Ni2/Al3Ni core–shell intermetallics within its matrix produced via powder metallurgy, was subjected to isothermal compression tests at different conditions so as to garner an insight into its hot deformation behaviour. These experiments were conducted from 300 to 500 °C, with strain rates varying from 0.0001 s−1 to 0.1 s−1. It is found that the flow stress is influenced by both strain rate and temperature. As the deformation temperature reduced or the strain rates increased, the peak stress level increased. To characterize the flow stress of the composite, a sine-hyperbolic constitutive equation was developed and the calculated value of activation energy (234 kJ/mol) was substantially higher than that for the self-diffusion of pure Al. Subsequently, the strain-compensated Arrhenius model and the artificial neural network (ANN) model were developed to predict the composite flow behaviour. With a lower average absolute relative error of 2.266%, a smaller root means square error of 0.668 MPa, and a higher correlation coefficient of 0.999 than the Strain-compensated Arrhenius model, the ANN model is more predictable. The processing maps show that the ideal hot working conditions for the composite are between 400 and 500 °C, with strain rates between 0.0001 s−1 and 0.01 s−1 with an efficiency of 37%. The uneven distribution in the shape and size of Core–shell/Al3Ni intermetallic compounds influenced the flow stress curves, leading to dynamic recrystallization (DRX), followed by partial dynamic recovery (DRV), and ultimately strain hardening at 0.01 s−1 & 0.1 s−1. The occurrence of recrystallization and recovery up to a specific strain followed by strain hardening at all the deformation temperatures is a rare phenomenon and has been attributed to the structure and composition of core–shell intermetallics. The occurrence of work hardening at higher strains throughout the operational range of temperatures imparts greater reliability to structural components. [ABSTRACT FROM AUTHOR]

Titanium alloy, Ti–6Al–2.2Mo–1.4Cr–0.4Fe–0.3Si (BT3-1), is a two phase α + β alloy developed for applications in rocket engines, gas turbine engines, and aircraft frames for service up to a temperature of 450 °C. The hot workability of this alloy has been studied through isothermal hot compression testing in the temperature and strain rate (ε ˙) range of 800 °C to 1000 °C and 10−3 to 10 s−1, respectively, in a thermomechanical simulator. Processing maps using dynamic material model has been generated and different regions of the map were correlated with microstructural observations. The flow stress data were fitted in Arrhenius strain-compensated model and constitutive equations were developed. Optical microstructures revealed elongated grains, kinking of α phase, flow localisation, and adiabatic shear bands at lower temperatures. Super-plasticity was found to be operative at low temperature of 850 °C and ε ˙ 10−3 s−1, whereas dynamic recrystallization (DRX) was dominating at high temperatures of 950 °C to 1000 °C and ε ˙ of 10−3 s−1. Finite element analysis showed the flow localization in the unstable regions of processing map. Enhanced hot workability was achieved above 950°C in the ε ˙ of 10−2−10−3 s−1 due to initiation of DRX in view of an increase in the β phase fraction. [ABSTRACT FROM AUTHOR]

The liner is affixed to the inner side of the ball mill cylinder to protect the cylinder. Through isothermal compression experiments, Arrhenius constitutive models, peak strain models, critical strain models, dynamic recrystallization dynamic models, and grain size models suitable for the forging process of Mn–Cr–Ni–Mo steel used in ball mill liners were established. By utilizing Deform software, a 3D thermo‐force‐structure coupling model for the hot forging process of ball mill liners was constructed, and the volume fraction of dynamic recrystallization and average grain size during forging was predicted. The response surface model was employed to investigate how process parameters interacted with each other and affected microstructure uniformity in ball mill liners. After optimization, the optimal parameters were determined: initial forging temperature at 1200 °C, forging speed at 30 mm s−1, and friction coefficient at 0.3. Subsequently, a hot forging experiment on ball mill liners was conducted using these optimized parameters; samples were analyzed through backscattered electron diffraction device experiments and microscopic tissue observations. Results demonstrated that microstructural changes observed during actual forging processes aligned with numerical simulation results—thus verifying both the accuracy of the Mn–Cr–Ni–Mo steel material model and numerical simulation method. [ABSTRACT FROM AUTHOR]

In this article, Fe–8.5Mn–1.5Al medium‐manganese steel is taken as the research object, and Gleeble 3500 thermal simulation testing machine is used to conduct isothermal compression at different deformation temperatures, strain rates, and strains in its austenite ferrite two‐phase zone. A constitutive model and a dynamic recrystallization volume fraction model for materials are established, and finite‐element method is used to simulate the temperature, equivalent strain, and dynamic recrystallization volume fraction distribution in different regions of the workpiece under different deformation conditions. By comparing and analyzing the microstructure, finite‐element simulation results, and hot working diagrams obtained from the experiment, the microscopic mechanism of dynamic softening of the material when ferrite and austenite coexist is explained; the transformation of the dynamic softening mechanism of the two phases with the hot deformation process is also explained. Early deformation mainly occurs in softer ferrite, which preferentially undergoes continuous dynamic recrystallization. Austenite has a lower stacking fault energy, and discontinuous dynamic recrystallization (DDRX) occurs when the dislocation density reaches a certain critical value. At the same time, when the strain reaches a certain level, the dynamic softening behavior of ferrite will also transform into DDRX. The optimal deformation conditions for Fe–8.5Mn–1.5Al medium‐manganese steel during warm processing in the two‐phase zone are a temperature of 720 °C, a strain rate of 0.01 s−1, and a large deformation zone. [ABSTRACT FROM AUTHOR]

Solidification structure and segregation behavior of S31254 superaustenitic stainless steel ingot containing 0 wt% B and 0.005 wt% B are investigated. The results show that serious element segregation and massive eutectics are present in the center of the ingot. By contrast, the addition of boron reduces the secondary dendrite spacing, the degree of elemental segregation, and the σ phase. Further, the effect of boron on the solidification process is studied by using the high‐temperature confocal laser scanning microscope and combined with Thermo‐Calc thermodynamic simulation results. The results show that boron can widen the solidification temperature range and greatly retard the matrix solidification. The role of boron in refining dendrite structure and inhibiting precipitation is further confirmed. The effect of boron on the constitutive equation of S31254 superaustenitic stainless steel has also been researched through isothermal compression testing in the temperature range of 950–1200 °C and strain rate range of 0.01–10 s−1. The activation energy of the boron‐free and boron‐containing S31254 superaustenitic stainless steels based on the constitutive equation are 427.77 and 495.80 kJ mol−1, respectively. Processing maps indicate that the instability domain is significantly reduced and the hot ductility is improved after the addition of B. [ABSTRACT FROM AUTHOR]

The evaluation of the hot workability of 5Cr5MoSiV1 steel with high deformation resistance is crucial for the controllability of the hot forging process. Based on the isothermal compression at deformation temperature of 950–1200 °C and strain rate of 0.01–10 s−1, the flow behavior of 5Cr5MoSiV1 steel is demonstrated. As the strain rate increases, the typical characteristics of the true stress–strain curve indicate that the dynamic softening mechanism changes from dynamic recrystallization to dynamic recovery. Moreover, the hot working window determined by the hot processing map from the modified J–C constitutive model is constructed for the forging process of the material. Through microstructure verification, the optimal hot working window is within the range of deformation temperature from 1000 to 1185 °C and strain rate from 0.01 to 0.202 s−1. Furthermore, the forging upsetting tests of the large cylindrical specimens are used to confirm the insecurity of hot deformation parameters outside the optimum hot working window. The implementation of this study can provide a theoretical basis for the determination of hot forging process parameters for 5Cr5MoSiV1 steel. [ABSTRACT FROM AUTHOR]

The hot deformation behavior of 22Cr‐25Ni austenitic heat‐resistant steel at the temperatures of 950–1150 °C and strain rates of 0.01–10 s−1 is studied by isothermal compression test. It is found that the dynamic recrystallization (DRX) degree of the steel increases with the increase of temperature. The DRX degree decreases with the increase of the strain rate from 0.01 to 1 s−1, whereas the DRX degree increases with the increase of the strain rate from 1 to 10 s−1. The hot deformation activation energy is as high as 624.25 kJ mol−1 due to the addition of a large number of alloying elements. The typical strain compensation Arrhenius constitutive model established can be used to roughly predict the hot flow behavior of the steel. Furthermore, a modified model considering the influence of strain rate and deformation heat on the deformation process is proposed and showed higher accuracy (statistical parameters r = 0.994 and average absolute relative error = 4.59%). The DRX zone of the steel is determined to be 1080–1150 °C/0.01–0.1 s−1 through processing map analysis, representing the appropriate hot working zone. The microstructure corresponding to the instability zone in the processing map exhibits deformation concentration bands or necklace structures. [ABSTRACT FROM AUTHOR]

Isothermal constant-strain-rate compression experiments of S280 ultrahigh-strength stainless steel were conducted at 800–1150 °C, 0.001–10 s−1, and 70% height reduction. The flow stress behaviors were analyzed based on the compression data. The strain compensation Arrhenius constitutive relation, multiple linear regression constitutive relation, and back-propagation (BP) neural network constitutive relation of this alloy were established for the first time. The S280 ultrahigh-strength stainless steel is characterized by a positive strain rate and negative temperature sensitivity. Its flow stress at high temperature (1000–1150 °C) and low temperature (800–950 °C) is generally at the steady state and the softening state, respectively. The three new flow stress constitutive relations all meet the requirements for engineering applications in terms of predictive precision. The BP neural network constitutive relation shows the highest predictive precision, with correlation coefficient R of 0.999 and average absolute relative error AARE of 1.04%. The strain compensation Arrhenius constitutive relation shows the lowest predictive precision, with R of 0.994 and AARE of 14.748%. The multiple linear regression constitutive relation shows the modest predictive precision, with R of 0.994 and AARE of 6.24%. [ABSTRACT FROM AUTHOR]

In this work, the deformation behavior of Al-8.1Zn-2.0Mg-1.0Cu-0.2Ag-0.15Zr alloy was studied under isothermal compression, with strain rate and temperature in the range of 0.001 s−1−10 s−1 and 330 °C−450 °C, respectively. First, it was found that the deformation temperature significantly affected the dynamic recrystallization (DRX) and phase transformation behaviors of this alloy. At 330 °C, discontinuous dynamic recrystallization (DDRX) and arched grain boundaries were observed, whereas dislocation entanglements dominated continuous dynamic recrystallization (CDRX) was notably detected at 370 °C. Temperatures exceeding 410 °C facilitated the CDRX behavior, as polygonal chain-like subgrains and block-like dislocation loops were found within the new grains. High deformation temperatures also resulted in the amalgamation and growth of adjacent subgrains. Moreover, we found the Ag-containing phase spheroidized and grew at high temperatures, while the deformation had little effect on the Al3Zr. Strain rate also significantly affected the deformation behavior of this alloy. Samples deformed at 0.001 s−1 exhibited prolonged deformation time with clear dynamic recovery (DRV) and DRX. At 1 s−1, irregular dislocation distribution was observed, while at 10 s−1, shear band formation induced by deformation instability was evident. Furthermore, the deformation induced η′/matrix interfacial transformation from Zn clusters to a Zn–Mg common interface. Particularly, the precipitation order at grain boundary was proved to be Zn atomic clusters → Zn, Mg atomic clusters (GP zone) → η′ (MgZn2).

In this paper, isothermal thermal compression tests were carried out on Al–Zn–Mg–Cu alloys at varying deformation temperatures (360°C∼440°C) and strain rates (0.001s−1∼10s−1) using a Gleeble-3500C thermal simulation tester. Based on the true strain stress data obtained from the tests, the flow behavior of Al–Zn–Mg–Cu alloys during thermal deformation was investigated. Through a comprehensive consideration of deformation temperature, strain rate, and strain compensation, a high-precision constitutive model was established. Additionally, the specimens subjected to hot compression were further treated with solution annealing for different durations (0 h–2 h) to investigate the static recrystallization (SRX) behavior and the associated microstructural evolution of the alloy during the solution treatment process. Electron Backscatter Diffraction (EBSD) was employed to characterize the microstructure evolution of Al–Zn–Mg–Cu alloy under various deformation and solution treatment conditions. The EBSD data were further processed and analyzed using the MTEX toolbox. The results revealed that dynamic recovery (DRV) is the predominant softening mechanism during the deformation process, accompanied by a small amount of dynamic recrystallization (DRX). The dynamically recrystallized grains exhibit a random crystallographic orientation. Further investigation showed that low temperature and high strain rate conditions are unfavorable for the occurrence of dynamic recovery and dynamic recrystallization during the thermomechanical processing. However, dislocations accumulated during deformation provided sufficient stored energy for the growth of static recrystallized grains during subsequent solution treatment, with static recrystallized grains predominantly forming at grain boundaries.

Within the realm of sustainable heating technologies, this study examines the performance of a Stirling heat pump employing chemically reactive working fluids in contrast to conventional inert counterparts. Reactive working fluids are energy vectors that enable the conversion of not only thermal but also chemical energy within the heat pump. The investigation spans a wide range of theoretical reactive gaseous mixtures, leveraging the ideal gas mixture thermodynamic model. Each fluid is characterized by an equilibrated chemical reaction, denoted as A 2 (g) ⇄ 2 A (g) , and distinguished by a set of reaction coordinates: the standard entropy change of reaction and standard enthalpy change of reaction. The chemical reaction evolution and thermodynamic properties are observed in each transformation, and the overall coefficient of performance (COP) of the system is evaluated and benchmarked against that of comparable inert working fluids. It is observed that the exothermic reaction during isothermal compression significantly increases the thermal energy supplied to the heat sink, as well as the thermal energy density per unit maximum volume, by up to 269 %, compared to an inert gas system. However, for the majority of reactive fluids studied, chemical reactions introduce irreversibility in the internal regenerator due to heat transfer across a finite temperature difference, contrary to the case of inert working fluids, penalizing the COP. Consequently, a reduction of up to 28 % in the COP is observed. Nevertheless, there exists a range of reactive fluids, characterized by reversible heat exchange in the internal regenerator, offering increased thermal energy transfer to the heat sink without compromising the COP. [ABSTRACT FROM AUTHOR]

Data-driven machine learning techniques can be useful for the rapid evaluation of material properties in extreme environments, particularly in cases where direct access to the materials is not possible. Such problems occur in high-throughput material screening and material design approaches where many candidates may not be amenable to direct experimental examination. In this paper, we perform an exhaustive examination of the applicability of machine learning for the estimation of isothermal shock compression properties, specifically the shock Hugoniot, for diverse material systems. A comprehensive analysis is conducted where effects of scarce data, variances in source data, feature choices, and model choices are systematically explored. New modeling strategies are introduced based on feature engineering, including a feature augmentation approach, to mitigate the effects of scarce data. The findings show significant promise of machine learning techniques for design and discovery of materials suited for shock compression applications. [ABSTRACT FROM AUTHOR]

Graphene/copper composites are promising in electronic and energy fields due to their superior conductivity, but microstructure control during thermal mechanical processing (TMP) remains a crucial issue for the manufacturing of high-performance graphene/copper composites. In this study, the hot deformation behavior of graphene/copper composites was investigated by isothermal compression tests at deformation temperatures of 700~850 °C and strain rates of 0.01~10 s−1, and a constitutive equation based on the Arrhenius model and hot processing map was established. Results demonstrate that the deformation mechanism of the graphene/copper composites mainly involves dynamic recrystallization (DRX), and such DRX-mediated deformation behavior can be accurately described by the established Arrhenius model. In addition, it was found that the strain rate has a stronger impact on the DRX grain size than the deformation temperature. The optimum deformation temperature and strain rate were determined to be 800 °C and 1 s−1, respectively, with which a uniform microstructure with fine grains can be obtained. [ABSTRACT FROM AUTHOR]

Herein, the hot deformation behavior of a near-α Ti-5Al-1Sn-1 V-1Zr-0.8Mo (Ti-5111) titanium alloy was studied at 870-1050 °C during isothermal compression tests at a strain rate of 0.01-10.0 s−1. The microstructural evolution mechanism in the titanium alloy was systematically analyzed. Results show that the flow stress values rapidly increase to the peak value and gradually decrease as the strain variable increases. Further, the peak stress declines with the increasing deformation temperature. The apparent activation energy values of (α + β) and β regions are 438 and 206 kJ mol−1, respectively. The variation of flow stress against temperature and strain rate is established using the constitutive equation. The safe processing zones are 890-960 °C and 960-1010 °C at strain rates of 0.01-0.3 s−1 and 0.1-2 s−1, respectively, as determined using the hot processing diagram. The maximum energy dissipation efficiency is 0.59 at 0.01 s−1 and 930 °C, which is the optimum processing technique. The flow instability for the Ti-5111 alloy will occur at a high strain rate when shear bands and microscopic cracks appear in the deformed microstructures. Therefore, processing Ti-5111 alloy in unstable zones of the hot processing diagram should be avoided. [ABSTRACT FROM AUTHOR]

Ferromagnetic shape memory alloys attracted increasing interest as multicaloric materials for solid state refrigeration. The most effective field coupling is achieved through the combination of the magnetic and mechanical induction of thermoelastic martensitic transformation. In the present work, we present an experimental investigation on NiMnGaCu polycrystalline cast alloy, by means of an experimental setup for compression tests in isothermal conditions under a longitudinal magnetic field. The setup has been ad hoc designed and developed specifically for this purpose. In this way, we can measure the elastocaloric and magnetocaloric effect at the same time. Moreover, the evolution of the entropy changes ΔS and the functional caloric parameters vs the magnetic field is evaluated. The application of magnetic field seems to act like a supplementary mechanical longitudinal stress. These preliminary results are fundamental to achieve a comprehensive understanding and modeling of coupled multicaloric phenomena. [ABSTRACT FROM AUTHOR]

Isentropic (adiabatic) compression of superheated vapor in vapor compression refrigeration cycles usually results in some discharge superheat, i.e. the discharge temperature exceeding the condensing temperature. Large discharge superheat reduces both operating range and compression efficiency. Sub-isentropic compression with heat rejection to the heat sink is therefore superior to adiabatic compression, as it results in lower discharge superheat and improved efficiency. However, significant temperature reduction by heat transfer through the working chamber walls is difficult to facilitate in common refrigeration compressors, particularly reciprocating compressors. Refrigerant and oil injection is a well-established method for reducing temperatures and increasing efficiency in screw and scroll compressors, as well as multi-stage systems. In comparison, effective methods for temperature reduction in single-stage reciprocating compressors are fairly limited. Therefore, a concept for high-pressure liquid injection is proposed. By means of a pump and injection valve, high-pressure liquid refrigerant is injected into the working chamber and atomized. The compressed gas is cooled through the evaporation of the injected liquid. The injection valve allows for control over the injection timing and quantity, enabling adjustment of the temperature profile, which is a major distinction from existing refrigerant injection methods. The coupled compression-injection process is evaluated for various refrigerants using an energetic chamber model. The injection is found to be particularly suitable for refrigerants with a large evaporation heat and a shallow dew line slope. For the example of ammonia, a theoretical reduction in compression work of 8.9% at an evaporation temperature of −10 °C and a condensing temperature of 45 °C is found. • Proposal of high-pressure liquid injection for reciprocating compressors. • Theoretical evaluation using energetic chamber model. • Potential for significant efficiency improvement compared to isentropic compression. • Increased operating range due to reduced discharge temperature. [ABSTRACT FROM AUTHOR]

Thermal simulation isothermal uniaxial compression experiments were carried out with Cube, Copper and S oriented aluminum single crystal(ASCs) at 25 〜300 °C and 0. 001 〜10 s-1. The true stress true strain curves of ASCs under different high temperature deformation conditions were obtained, and the strain compensation constitutive equation and thermal processing diagram were established. The results show that the degree of dynamic recrystallization(DRX) of ASCs with different crystal orientations is significantly different The DRX difficulty of ASCs with three orientations is as follows: Cube> CopperThe flow stress of ASCs during isothermal uniaxial compression decreases with the decrease of strain rate and the increase of deformation temperature. The maximum flow stress level of each orientation is Copper>S>Cube. The microstructure evolution energy dissipation of ASCs with different orientations during deformation is different, and the order of the power dissipation rate is Cube> Copper〉S. [ABSTRACT FROM AUTHOR]

Achieving superior properties in hot working demands the integration of constitutive modeling, precise microstructure control, and the rigorous identification of safe and efficient conditions. To address this, a powder metallurgy Al–Zn–Mg alloy underwent isothermal compression tests under conditions of 300–500 °C and 0.1–0.0001 s−1. The experimental outcomes indicate that the flow stress of the Al–Zn–Mg alloy exhibits dynamic recrystallization as the predominant softening mechanism observed across all investigated hot working parameters. An Arrhenius-type model integrated with strain was constructed to describe its hot working behavior. Establishing processing maps, while considering the effect of strain, facilitated the assessment of the workability of the Al–Zn–Mg alloy. Constructed processing maps suggest that recommended processing conditions fall within the range of 475–500 °C and 0.001–0.0001 s−1, revealing the presence of uniform equiaxed grains and recrystallized structures. Samples compressed at 300 °C/0.1 s−1 exhibited adiabatic shear bands and partial recrystallization, while microcracks were found in samples deformed at 400 °C/0.1 s−1 and 500 °C/01 s−1. The microstructural changes were analyzed using EBSD, employing various maps, including IPF, KAM, GOS, and GAM, to assess dislocation density, grain misorientation, and their correlation with recrystallization in relation to both strain rate and temperature. [ABSTRACT FROM AUTHOR]

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The material constitutive equation of 25CrMo4 steel was established through an isothermal compression experiment. First, a thermal compression experiment was carried out with a Gleeble-3500 thermal simulator to study the thermoplastic deformation behaviour of 25CrMo4 steel at various temperatures (850, 950, 1050, and 1150 °C) and strain rates (0.01, 0.1, 1.0, and 10 s−1). The measured true stress–strain curve showed that when the temperature is constant, the flow stress increases with the strain rate, whereas when the strain rate is constant, the flow stress decreases with the temperature. Then, the constitutive model of peak stress of 25CrMo4 was established after analyzing the stress and strain statistics. The model parameters were optimized. The accuracy of the flow stress constitutive model was verified by comparing the flow stress prediction model with the experimental results. The hot forging process of the inner core wheel was numerically simulated based on DEFORM-3D v11 software, and the parameters of this process were formulated by analyzing the metal flow rate and equivalent stress and strain fields. [ABSTRACT FROM AUTHOR]

Copyright of Materials & Technologies / Materiali in Tehnologije is the property of Institute of Metals & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Laasraoui segmented and Arrhenius flow stress model, dynamic recrystallization (DRX) model, grain size prediction model, and hot processing map (HPM) of Fe-Cr-Mo-Mn steels were established through isothermal compression tests. The models and HPM were proven by experiment to be highly accurate. As the deformation temperature decreased or the strain rate increased, the flow stress increased and the grain size of the Fe-Cr-Mo-Mn steel decreased, while the volume fraction of DRX (Xdrx) decreased. The optimal range of the hot processing was determined to be 1050–1200 °C/0.369–1 s−1. Zigzag-like grain boundaries (GBs) and intergranular cracks were found in the unstable region, in which the disordered martensitic structure was observed. The orderly packet martensite was formed in the general processing region, and the mixed structure with incomplete DRX grains was composed of coarse and fine grains. The microstructure in the optimum processing region was composed of DRX grains and the multistage martensite. The validity of the Laasraoui segmented flow stress model, DRX model, grain size prediction model, and HPM was verified by upsetting tests. [ABSTRACT FROM AUTHOR]

Isothermal compression tests for ERNiCrMo-3 alloy specimens were conducted under temperatures of 990–1170 °C with strain rates of 0.01–10 s−1. Hot deformation behavior of ERNiCrMo-3 was analyzed based on the obtained flow stress curves. Three constitutive models were developed to anticipate the flow stress: the Arrhenius model compensated by strain, the Arrhenius model optimized by genetic algorithm (GA), and the artificial neuron network (ANN) model. The correlation coefficient (R) and average absolute relative error (AARE) were used to assess the predictive ability for these three models. The R values of the strain-compensated, GA optimized, and ANN models were 91.04, 93.54, and 99.01%, respectively, while the AARE values were 12.30, 8.19, and 2.92%, respectively. Furthermore, the absolute relative error of the ANN model was the most concentrated and mainly around 0. Therefore, the ANN model provides the maximum predictability and accuracy for flow stress. The ANN model was implemented via subroutine USRMTR in DEFORM 2D to simulate the hot compression process of the ERNiCrMo-3 alloy specimens. The numerical results were in good agreement with the experimental results, indicating a high potential for applicability to actual production processes. Finally, hot working characteristic of ERNiCrMo-3 alloy was analyzed by processing map and microstructural investigation. According to the result, the suitable thermal processing domain for ERNiCrMo-3 alloy should be at a temperature range of 1130–1170 °C and a strain rate range of 0.03–0.36 s−1. [ABSTRACT FROM AUTHOR]

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Gas separation such as CO 2 from N 2 in flue gas is an important step in reducing greenhouse gas emission. We discuss a separation method that moves mixed gas between two tracks at different pressures with ever-increasing purity at each stage along the tracks. Designs for adsorbents driven by volumetric pumps and membranes driven by a pressure drop are illustrated. For selectivity exceeding 10 in a three-stage system, the purity of the CO 2 output is 97.8% with 99.75% recovered. For a six-stage example, the purity of CO 2 is 99.996% and 99.9996% is recovered. The cost of compression is estimated from the number of times the two components have to be pressurized as they move between the tracks. For large selectivity, the effective number of times for CO 2 is 2 for the adsorbent case and 3 for the membranes in the three-stage design; these numbers are 5 and 6 in the six-stage design. As a result, the compressional energy requirement per input mole is R T ln ⁡ (C) (1 + A f) in the isothermal case for compression factor C , effective number of re-compressions A , and input CO 2 fraction f. This compressional energy exceeds the minimum energy from entropy by the factor ∼ (1 + A f) / f if C = 1 / f for efficient membrane use. [ABSTRACT FROM AUTHOR]

The hot deformation behavior and mechanism of Ti65 alloy with a bimodal microstructure were investigated by isothermal compression experiments conducted on the Thermecmastor-Z simulator equipment at temperatures ranging from 950 to 1110 °C and strain rates ranging from 0.01 to 10.0 s−1. The Arrhenius constitutive model, based on strain compensation, and Grey Wolf optimization-neural network with back propagation model (GWO–BP), were both established. The differences between the experimental and predicted value of flow stress were compared and analyzed using the two models. The results show that the prediction accuracy of GWO–BP in the two-phase region is higher than that of Arrhenius model. In the single-phase region, both methods demonstrated high prediction accuracy. Compared to the single-phase region, the flow stress of Ti65 alloy shows a higher degree of softening in the two-phase region. During deformation in the two-phase region, the initial lamellar α phase transformed from a kinked and elongated morphology to a globularized topography as the strain rate decreased. Boundary-splitting was the primary mechanism leading to the spheroidization process. The degree of recrystallization increased with the increase in strain rate during the deformation in the single-phase region, while dynamic recovery and strain-induced grain boundary migration were the main deformation mechanisms at a lower strain rate. Discontinuous dynamic recrystallization may be the dominant recrystallization mechanism under a high strain rate of 10 s−1. [ABSTRACT FROM AUTHOR]

During thermal deformation, grain coarsening due to grain growth and grain refinement resulting from dynamic recrystallization (DRX) collectively influence the deformed grain size. To investigate the separative and comprehensive effects of the two mechanisms in the Ni-38Cr-3.8Al alloy, grain growth experiments and isothermal compression tests were conducted. Kinetics models for grain growth and DRX behaviors were established based on the experimental data, which were integrated with finite element (FE) techniques to simulate the evolution of grain size throughout the entire thermal compression process. The effects of grain coarsening and grain refinement during this process were separated and quantified based on the simulation data. The results revealed that grain coarsening predominated during the heating and holding stages, with a longer holding time and higher holding temperatures intensifying this effect. However, during the compression stage, grain coarsening and grain refinement co-existed, and their competition was influenced by deformation parameters. Specifically, grain refinement dominated at strain rates exceeding 0.1 s−1, while grain coarsening dominated at lower strain rates (<0.1 s−1) and higher deformation temperatures (>1373 K). The simulated grain sizes closely matched the experimental observations. [ABSTRACT FROM AUTHOR]

The performance degradation of electrical submersible pump (ESP) caused by high gas volume fraction (GVF) has always been a common problem in the field of oil and gas production. Experiments are conducted to investigate the gas-liquid performances of pressurization, power, and efficiency of a 15-stage mixed-flow ESP self-designed and manufactured. A calculation method of gas-liquid useful power is proposed based on the hypothesis of isothermal compression, with the relative error of calculated results within ±2% between isothermal compression and polytropic compression. The rapid decrease of useful power is found to be the main reason for the rapid decrease of hydraulic efficiency as the pump-inlet gas volume fraction (IGVF) increases. Moreover, the interstage pressurization deterioration gradually weakens along the increasing direction of stage number. The calculation method of interstage gas volume fraction is proposed, and the gas-liquid pressurization of each booster stage is found to follow the same distribution with the variation of interstage gas volume fraction. Increasing the stage number can efficiently improve the critical gas volume fraction of interstage pressurization deterioration, as well as the pressurization boundary and maximum value of average single-stage gas-liquid pressurization. The prediction correlations of gas-liquid operating conditions of the maximum pressurization and the highest hydraulic efficiency are established, respectively, and the gas-liquid condition range of high-efficiency pressurization is discovered. [ABSTRACT FROM AUTHOR]

The mechanical properties of metastable β-titanium alloys are highly susceptible during the thermal mechanical processing (TMP). In this process, the recrystallization process plays an important role in determining the microstructure and texture evolution. The implementation of dynamic recrystallization (DRX), a process for achieving β-grain refinement, is considered of great significance for the improvement of the properties of metastable β-titanium alloys and their industrial production. Along these lines, in this work, an isothermal compression test of TB8 titanium alloy was carried out by using a Gleeble-3500 thermal simulator. As a result, the rheological stress behavior was analyzed, the thermal processing map was accurately established based on the stress–strain curve, and the optimal processing interval was determined. The DRX kinetic and the DRX grain size models were developed, on the basis of which a new DRX intrinsic model was established to improve the material parameters. Therefore, the actual situation in the working process could be better predicted. The microstructural evolution of TB8 titanium alloy during thermal deformation was comprehensively investigated using the electron backscatter diffraction (EBSD) technique. The obtained results demonstrate a close correlation between the diversity of DRX mechanisms in TB8 alloy and the distribution of dislocation density. Four microstructural textures during thermal deformation were identified, in which the cube texture of (001) <010> and the R-Gorss Nd texture of (110) <110> dominate. Due to the random orientation of the dynamically recrystallized grains, the strength of the R-Gorss Nd texture of (110) <110> increases with the increase in the volume fraction of DRX. On the contrary, it was verified that the dynamic recrystallization behavior has a significant weakening impact on the cube texture of (001) <010>. [ABSTRACT FROM AUTHOR]

Six hot compression tests are conducted using the Gleeble3500 thermomechanical simulator to investigate the microstructural evolution and precipitation behavior in low‐C–Mn V‐microalloyed steel. The specimens are subjected to hot isothermal compression deformation of 87%. The optical microscopy and transmission electron microscopy using carbon extraction replica method are used to characterize the microstructures and precipitation after the simulated thermomechanical controlled process and coiling. The results indicate that increasing the finish rolling temperature benefits the refinement of ferrite grains but has little influence on the refinement of the precipitates. It is also observed that lower coiling temperatures (CTs) promote the formation of fine precipitates. When the CT is 500 °C, the average precipitate size is found to be 86 nm. Furthermore, it is found that the CT significantly influences the nucleation sites of the precipitates inter alia, the matrix, interphase, grain boundaries, and dislocations. As expected, at higher CTs, nucleation is predominantly on the defects rather than the matrix. [ABSTRACT FROM AUTHOR]

This study investigated the formation mechanism of new grains due to twin–twin intersections in a coarse-grained Mg–6Al–3Sn–2Zn alloy during different strain rates of an isothermal compression. The results of electron backscattered diffraction investigations showed that the activated twins were primarily { 10 1 ¯ 2 } tension twins, and 60° < 10 1 ¯ 0> boundaries formed due to twin–twin intersections under different strain rates. Isolated twin variants with 60° < 10 1 ¯ 0> boundaries transformed into new grains through lattice rotations at a low strain rate (0.01 s−1). At a high strain rate (10 s−1), the regions surrounded by subgrain boundaries through high-density dislocation arrangement and the 60° < 10 1 ¯ 0> boundaries transformed into new grains via dynamic recrystallization. [ABSTRACT FROM AUTHOR]

The hot deformation behavior of Al-Zn-Mg-Cu alloy was investigated by flow stress curves in isothermal hot compression experiments with deformation temperatures of 350–450 °C and strain rates of 0.01 s−1 to 1 s−1, and the constitutive equation of homogeneous alloy was obtained. At the same time, the dynamic recrystallization and precipitation behavior during hot deformation and the relationship between them and the Z parameters were studied by using EBSD and TEM. DRV is the main mechanism of dynamic softening. With the decrease in Z parameter, the softening mechanism changes from dynamic recovery to discontinuous dynamic recrystallization or continuous dynamic recrystallization. At a higher Z parameter, the dislocation density and precipitated phase density are also higher because the high dislocation density provides heterogeneous nucleation sites of the precipitated phase. A large number of precipitates in the alloy also inhibit the nucleation and growth of dynamic recrystallization by hindering dislocation movement and grain boundary migration. [ABSTRACT FROM AUTHOR]

Using experimental and LES methods, this paper investigates the effects of equivalence ratio and blockage ratio on hydrogen flame acceleration, explosion overpressure characteristics, and flow field properties in a closed obstructed duct. The study indicates that there is a positive correspondence between the flame acceleration and pressure rise in a closed duct. The continuous flame acceleration is driven by flow compression and turbulent combustion propulsion, corresponding to a rapid pressure rising. After the quasi-plane flame, the explosion overpressure begins to oscillate at a high frequency. As the blockage ratio increases, the turbulent combustion is intensified, consequently leading to a noticeable increase in flame velocity and pressure rising rate. While high obstacles exert an obstructive effect on the initial flame propagation and the pressure oscillations. The vorticity is mainly distributed in the shear flow region and the burned region, and its magnitude and distribution area increase with a higher obstacle ratio. • Correspondence between flame acceleration and overpressure characteristics is revealed. • The adiabatic and isothermal compression are analyzed in a closed obstructed duct. • Vector field and vorticity field at different blockage ratios are investigated. [ABSTRACT FROM AUTHOR]

To obtain the optimal hot deformation process, the rheological and dynamic recrystallization behaviors of A100 steel were researched through isothermal compression tests. Firstly, a Hensel-Spittel constitutive model was established based on the stress–strain curves. Secondly, dynamic recrystallization percentage and grain size models were established to identify the necessary conditions for complete dynamic recrystallization. Finally, microstructural analysis was employed to validate the accuracy of the recrystallization model. The results indicate that the flow stress is highly sensitive to both the strain rate and the temperature, and the HS model demonstrates a high predictive accuracy, with a correlation coefficient of 0.9914. There exists a contradictory relationship between decreasing the average grain size and increasing the recrystallization percentage. The higher the percentage of dynamic recrystallization, the larger the average grain size tends to be. This situation should be avoided when devising the actual processing procedures. The optimal hot working processes for achieving complete dynamic recrystallization and a smaller average grain size are as follows: a strain equal to or greater than 0.6, a temperature between 1193 and 1353 K, and a strain rate between 0.1 and 1 s−1. [ABSTRACT FROM AUTHOR]

In this work, a new use of mixed Ti-6Al-4V powder, consisting of the retained powder after screening for additive manufacturing and the recycled powder after multiple printing, has been exploited. The powder mixture has been hot-isostatically-pressed (HIPed) at 930 °C/120 MPa for 3 h to reach full density. The hot deformation behavior of the as-HIPed powder compacts were investigated through isothermal compression tests, kinetic analyses, and hot processing maps. Finally, the optimized hot working parameters were validated using upsetting tests. The results show that the as-HIPed Ti-6Al-4V alloy has a fine and homogeneous microstructure. The activation energies were calculated to be 359 kJ/mol in the α + β phase regime and 463 kJ/mol in the β phase regime, respectively. The optimal hot working parameters are a deformation temperature above 950 °C and strain rate higher than 0.1 s−1. The hot workability of as-HIPed powder compacts is better than the as-cast billets. The deformed microstructure can be finer than that of as-HIPed state, and the mechanical performance can be further improved by the optimal thermo-mechanical processing treatment. [ABSTRACT FROM AUTHOR]

Hybrid compressed air energy storage (H-CAES) system can effectively reduce the heat loss in the compression process, which is one of the important methods to solve the problem of renewable energy volatility. Based on the H-CAES system that combines adiabatic compression and isothermal compression, this paper proposes a liquid piston compressor arrangement to adapt to the input power fluctuation and proposes a power allocation calculation method to solve the adiabatic compression and isothermal compression in the H-CAES system, with an emphasis on analyzing the impact of the participation of renewable energy sources on the system performance. In addition, the H-CAES system is placed under wind-solar-storage conditions, and scheduling strategies judged by time-sharing electricity price are proposed for different scenarios to explore the actual operating effects of the H-CAES system. The results show that the arrangement of liquid piston compressors from large tanks with fewer groups to small tanks with more groups can better adapt to the power change while maintaining a better isothermal compression effect. On the basis of using the power allocation calculation method proposed in this paper, it is found that higher compressor outlet pressure and lower storage pressure can improve the system efficiency and economic benefits. The system is able to achieve 59.71% efficiency and 0.2261 annual return on investment at the compressor outlet pressure of 4 MPa. Finally, it is demonstrated that the combined operation of H-CAES and wind energy can serve to increase the operating income of the power plant, and a maximum of 8909.236 yuan in daily electricity generation revenue can be achieved. [ABSTRACT FROM AUTHOR]

The constitutive model refers to the mapping relationship between the stress and deformation conditions (such as strain, strain rate, and temperature) after being loaded. In this work, the hot deformation behavior of a Ni-Cr-Mo steel was investigated by conducting isothermal compression tests using a Gleeble-3800 thermal simulator with deformation temperatures ranging from 800 °C to 1200 °C, strain rates ranging from 0.01 s−1 to 10 s−1, and deformations of 55%. To analyze the constitutive relation of the Ni-Cr-Mo steel at high temperatures, five machine learning algorithms were employed to predict the flow stress, namely, back-propagation artificial neural network (BP-ANN), Random Committee, Bagging, k-nearest neighbor (k-NN), and a library for support vector machines (libSVM). A comparative study between the experimental and the predicted results was performed. The results show that correlation coefficient (R), root mean square error (RMSE), mean absolute value error (MAE), mean square error (MSE), and average absolute relative error (AARE) obtained from the Random Committee on the testing set are 0.98897, 8.00808 MPa, 5.54244 MPa, 64.12927 MPa2 and 5.67135%, respectively, whereas the metrics obtained via other algorithms are all inferior to the Random Committee. It suggests that the Random Committee can predict the flow stress of the steel more effectively. [ABSTRACT FROM AUTHOR]

Engine components, particularly exhaust valves, are manufactured by a specific forming process known as electric upsetting, which contributes to microstructures with finer grains which enhance the performance of these components. To this end, it is necessarily required to describe the grain evolution behaviors of heat-resistant alloys during the electrical-thermal-mechanical coupling forming process. The grain evolution behaviors of Ni80A superalloy including dynamic recrystallization (DRX) kinetics models and mesoscale cellular automaton (CA) model are solved from the acquired stress–strain curves in resistance heating isothermal compression tests. Following which, a multi-field and multi-scale coupling FEM model is established by embedding the multi-scale grain evolution models into the electrical-thermal-mechanical multi-field coupling compression model. Then the grain evolution behaviors in isothermal compressions with processing conditions are reproduced by simulations. The results reveal that during the isothermal compressions, recrystallized grains intend to bulge and generate around the original grain boundaries, representing as 'necklace' microstructures inhomogeneously distributed in the matrix, and then such grain morphology is gradually replaced by refined and equiaxed DRX grains. For a fixed strain, grain size decreases with decreasing temperature and increasing strain rate. Finally, the EBSD characterization results show that the developed FEM model can well describe the grain evolution behaviors of Ni80A superalloy in electrical-thermal-mechanical coupling compression process. [ABSTRACT FROM AUTHOR]

Amorphous ices are usually classified as belonging to low-density or high-density amorphous ice (LDA and HDA) with densities ρLDA ≈ 0.94 g/cm3 and ρHDA ≈ 1.15−1.17 g/cm3. However, a recent experiment crushing hexagonal ice (ball-milling) produced a medium-density amorphous ice (MDA, ρMDA ≈ 1.06 g/cm3) adding complexity to our understanding of amorphous ice and the phase diagram of supercooled water. Motivated by the discovery of MDA, we perform computer simulations where amorphous ices are produced by isobaric cooling and isothermal compression/decompression. Our results show that, depending on the pressure employed, isobaric cooling can generate a continuum of amorphous ices with densities that expand in between those of LDA and HDA (briefly, intermediate amorphous ices, IA). In particular, the IA generated at P ≈ 125 MPa has a remarkably similar density and average structure as MDA, implying that MDA is not unique. Using the potential energy landscape formalism, we provide an intuitive qualitative understanding of the nature of LDA, HDA, and the IA generated at different pressures. In this view, LDA and HDA occupy specific and well-separated regions of the PEL; the IA prepared at P = 125 MPa is located in the intermediate region of the PEL that separates LDA and HDA. Recently, a medium-density amorphous ice (MDA) was synthesized via ball-milling of hexagonal ice, adding complexity to our understanding of the phase diagram of supercooled water and amorphous ice. Here, the authors use molecular dynamics simulations to show that, depending on the employed pressure, isobaric cooling can generate a continuum of amorphous ices with densities that expand in between those of low- and high-density amorphous ices, with some of these amorphous ices being remarkably similar to MDA. [ABSTRACT FROM AUTHOR]

Single-pass isothermal hot compression tests on four medium-Mn steels with different C and Al contents were conducted using a Gleeble-3500 thermal simulation machine at varying deformation temperatures (900–1150 °C) and strain rates (0.01–5 s−1). Based on friction correction theory, the friction of the test stress–strain data was corrected. On this basis, the Arrhenius constitutive model of experimental steels considering Al content and strain compensation and hot processing maps of different experimental steels at a strain of 0.9 were established. Moreover, the effects of C and Al contents on constitutive model parameters and hot processing performance were analyzed. The results revealed that the increase in C content changed the trend of the thermal deformation activation energy Q with the true strain. The Q value of 2C7Mn3Al increased by about 50 KJ/mol compared with 7Mn3Al at a true strain greater than 0.4. In contrast, increasing the Al content from 0 to 1.14 wt.% decreased the activation energy of thermal deformation in the true strain range of 0.4–0.9. Continuing to increase to 3.30 wt.% increased the Q of 7Mn3Al over 7Mn by about 65 KJ/mol over the full strain range. In comparison, 7Mn1Al exhibited the best hot processing performance under the deformation temperature of 975–1125 °C and strain rate of 0.2–5 s−1. This is due to the addition of C element reduces the δ-ferrite volume fraction, which leads to the precipitation of κ-carbides and causes the formation of microcracks; an increase in Al content from 0 to 1.14 wt.% reduces the austenite stability and improves the hot workability, but a continued increase in the content up to 3.30 wt.% results in the emergence of δ-ferrite in the microstructure, which slows down the austenite DRX and not conducive to the hot processing performance. [ABSTRACT FROM AUTHOR]

During the thermal deformation of aluminum alloy materials, the deformation conditions such as deformation volume, temperature and strain rate are important factors that influence the deformation mechanisms such as work hardening, dynamic recovery and dynamic recrystallization. Under the interaction of different deformation mechanisms, the properties of aluminum alloy materials will change significantly. In this study, isothermal hot compression experiments were conducted on the Al-7.92 Zn-1.64 Mg-2.00 Cu alloy to analyze its hot flow behavior (T = 250~450 °C, ɛ̇ = 0.001~1 s−1). The obtained flow behavior data were used to construct an Arrhenius-type constitutive equation and processing maps, investigating organizational evolution under diverse hot deformation conditions. The results show that the energy dissipation rate can reach 0.37 when the deformation temperature T = 380~450 °C and the strain rate ɛ̇ < 0.1 s−1, suggesting that the material is most suitable for thermal deformation processing at high temperatures and low strain rates. At a strain rate of 0.1 s−1 and a temperature of 450 °C, the percentage of recrystallized grains and substructures increased by 7.20% and 3.14%, respectively, compared to 300 °C, which is due to the severe dynamic recovery and dynamic recrystallization. At 350 °C and 0.1 s−1, there was a higher percentage of recrystallized grains and substructures, 5.44% and 5.87% higher, respectively, than at a strain rate of 1 s−1, indicating that the release of dislocation accumulation due to deformation storage energy will be more favored at low strain rates, which promotes the enhancement of the dynamic recrystallization mechanism. [ABSTRACT FROM AUTHOR]