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In numerous engineering applications, the occurrence of highly rapid loading conditions, coupled with significant temperature rise, is prevalent. Under these harsh conditions, shear localization is a prominent material failure mechanism, which may result in catastrophic failure. Generally, materials possessing higher strength, limited work hardening rate, and lower thermal conductivity are more prone to mechanical instability. However, in the current study, a cryo-rolled CoCrNi alloy, characterized by much higher strength and limited work hardening, shows remarkable room and high-temperature mechanical performance under impact loading except at one temperature domain∼600 °C where this material displays mechanical instability by exhibiting adiabetic shearband. To shed light and understand this abnormal mechanical response, an in-depth microstructural study revealed that the ASB formation is closely linked to the recrystallization behavior of this alloy that is invariantly related to the stored energy of cold work, test temperature, and strain rate. Uniquely, the amplified nano-twinning activity at high strain rate and critical temperature promoted the fragmentation of grains and facilitated recrystallization, respectively. Once the recrystallization is completed, the alloy regains work hardening ability even at very high test temperatures, reaching 900 °C due to the deformation of the newly recrystallized matrix. The present work is valuable in delineating the alloy's application domain for rigorous impact and crash-worthiness applications, as there exists a dearth of literature on this material for dynamic scenarios. • Cryo-rolling introduces extensive twinning in CoCrNi. • Dynamic hot compression from room temperature to 900 °C. • Formation of shear band at only one critical temperature ∼600 °C,neither below nor above this temperature. • Dynamic strain rate induced secondary and tertiary twins fragment the deformed matrix into nano-sized blocks. • Shear band formation and propagation linked to stored energy of cold work and ambient test conditions. [ABSTRACT FROM AUTHOR]

Differential scanning calorimetry coupled with simultaneous evolved gas analysis (DSC-EGA) on aged δ-Pu samples shows that most radiogenic helium remains trapped within the Pu matrix at temperatures very close to, or slightly above, the melting temperature. Our results indicate that helium release from 50-year-old δ-Pu occurs as a burst just below the melting temperature (>0.994 T m), with subsequent pressure oscillations as temperature increases. Subordinate quantities of H 2 were also released along with helium. The helium emission tails off and ceases above ∼720 – 750°C. In a δ-Pu alloy aged 6 years, the initial helium burst occurs slightly above melting (∼1.015 – 1.042 T m), with a discrete, larger helium spike occurring between 670 and 686°C. The proximity of helium release to the liquidus transition presented challenges in the deconvolution of overlapping process enthalpies, the liquidus endotherm, and the exotherm resulting from bubble collapse, annealing and gas expulsion. Helium's strong affinity for vacancy binding in a 2He-vac configuration is predicted by Density Functional Theory (DFT) modeling. The measured stored energy associated with the He release events in a 50-year-old δ alloy is on the order of ∼10–11 J/g, which is significantly higher than stored energies measured in the sub-solidus regimes (∼2 J/g) that are related to the solid-state annealing of processing- and radiation-induced defects. This implies that aged δ Pu alloys have a remarkable resilience to accommodate the lattice strain produced by the internal pressure of the helium bubbles and provides further insight into the thermodynamic behavior of aged δ Pu. [Display omitted] • DSC-EGA analyses of aged δ-Pu samples document the emanation of a He + H 2 gas burst, while the metal is in the ε-phase. • During the 1st melt, an exothermic energy spike occurs immediately after the onset of normal endothermic melting. • Energy release during 1st melt is ∼10 J/g, corresponding to annealing of gas-filled voids formed due to self-irradiation. • Helium's affinity for vacancy binding, illustrated using DFT modeling, accounts for its abundance in the gas burst. • Aged δ−Pu alloys can accommodate lattice strain produced by gigapascal-scale internal pressures of He bubbles. [ABSTRACT FROM AUTHOR]

In the present investigation, equiatomic CoCrFeMnNi high entropy alloy (HEA) was subjected to 80% cold rolling (as-rolled) followed by isothermal annealing treatment at 700 °C for different time periods. Microstructural characterization was performed using electron back-scattered diffraction (EBSD) and electron channeling contrast imaging (ECCI) techniques on the as-rolled and annealed samples. The as-rolled microstructure consisted of elongated grains mainly composed of strong α-fiber and weak γ-fiber textures. The as-rolled sample showed the formation of ingrain SBs in the γ-fiber grains, which served as preferential sites for grain nucleation. The annealing treatment of as-rolled samples at 700 °C cause static recovery (SRV) before 5 minutes of heat-treatment, whereas static recrystallization (SRX) was observed after 5 minutes of heat-treatment in the CoCrFeMnNi alloy samples. A faster rate of recrystallization kinetics was observed after 15 minutes of heat-treatment. The annealing treatment reduced the intensity of α-fiber and enhanced the Copper, Cube and P ({011}<122>) texture components. Copper components originated from coarse recrystallized grains, which were the results of localized grain growth phenomena. Unusual behavior of banded featured α-fiber grains was observed during the annealing process. These banded grains in the partially annealed samples consisted of subgrain-boundaries and showed a delayed response to recrystallization as compared to grains with other orientations. Stored energy (SE) and Taylor factor (M) calculations were also used to understand the delayed recrystallization response of the banded featured/retained deformed grains. The microhardness value of the as-rolled sample was approximately 450 Hv, which decreased to around 230 Hv for the fully recrystallized grains. • Microstructural and texture evolution of the RTR+annealed CoCrFeMnNi HEA alloy were investigated. • Brass-oriented grains were showing the delayed in recrystallization. • Localized grain growth was observed for the Copper-oriented grains. • Copper-type shear bands were observed in the RTR CoCrFeMnNi sample. • The annealing treatment enhanced the Copper, Cube and P ({011}<122>) components. [ABSTRACT FROM AUTHOR]

Inhomogeneous deformation occurs in aluminum matrix composite, resulting in strain concentration near reinforcement/matrix interfaces. In this work, for the CNT/2024Al composite extruded by porthole die extrusion, the effects of reinforcements (CNTs and Al 4 C 3) and intermetallic (Al 2 Cu) on atomic strain concentration and grain boundary migration were systematically studied. The results indicate that obvious atomic strain concentration appears near the CNT/Al and Al 4 C 3 /Al interfaces, and then, the strain is transferred from the interfaces to Al matrix. Mirco-Al 2 Cu phases are mainly distributed at grain boundaries, increasing Zener force, and thus inhibit grain growth of the composite. In addition, the Al 4 C 3 /Al and Al 2 Cu/Al interfaces are observed, and the (111) Al atom plane is parallel to 1 ̄ 107 Al4C3 , while large number of misfit dislocations are observed near the Al 2 Cu/Al interface. Transmission Kikuchi diffraction and transmission electron microscope observations indicate that the grains, which contains more second phases, exhibit higher dislocation density than neighboring grains, providing driving force for grain boundary migration. High extrusion temperature brings about Al 2 Cu dissolution, leading to grain growth, and interfacial bonding strength decreases with increasing extrusion speed. Consequently, the composite extruded at low-temperature and low-ram speed has ultrafine grains, high dislocation density, and strong interfacial bonding, exhibiting high hardness, tensile strength and elongation. • Atomic strain concentration is illustrated by geometric phase analysis and molecular simulation. • The unevenly distributed dislocations in neighboring grains provide driving force for grain boundary migration. • Mirco-Al 2 Cu phases are dissolved at high temperature, leading to grain growth. • The composites extruded at low temperature and speed exhibits superior properties. [ABSTRACT FROM AUTHOR]

The selective 3D growth of multiple recrystallization nuclei/grains around a hardness indentation into a deformed Al grain has been quantified through a new approach that combines two synchrotron techniques: 3D X-ray Laue micro-diffraction and diffraction contrast tomography. The former is used to characterize the deformed microstructure and nucleation, while the latter to track the nuclei's growth during interrupted in situ annealing. The combined 4D (x,y,z,t) datasets enable a detailed quantification of the local deformed microstructure consumed by the nuclei/grains and the boundary characteristics between them, including the stored energy and anisotropy of the orientation distribution of the deformation matrix, as well as the misorientation of the moving and non-moving boundary segments. It is found that only certain nuclei can grow into large sizes, and the growth is heterogeneous both among recrystallizing grains and along different directions. Neither the local stored energy nor the boundary misorientation, whether considered individually or in combination, can fully account for the observed growing and shrinking behavior. The growth difference along different directions is related to the deformation microstructure, specifically the geometrical alignment of dislocation boundaries. Furthermore, the effects of impingement of other recrystallizing grains, recovery of the matrix, and elastic strain/stress, on the growth heterogeneities are discussed in detail with a view towards developing advanced modeling with improved predictability of local recrystallization phenomena. The present study demonstrates the effectiveness of the new approach in enabling 3D analysis of recrystallization in complex materials, with potential applications in the development of advanced engineering materials. [Display omitted] [ABSTRACT FROM AUTHOR]

(Na 0.5 Bi 0.5) 0.4 Sr 0.6 Ti 1- x Zr x O 3 relaxor ferroelectric ceramic were prepared by a traditional ceramic preparation process introducing Zr4+ at the B-site. It was observed that introducing an appropriate amount of Zr4+ ions into the NBST matrix can improve the energy storage efficiency. (Na 0.5 Bi 0.5) 0.4 Sr 0.6 Ti 0.5 Zr 0.5 O 3 shows excellent energy storage density up to 2.83 J/cm3, and excellent efficiency (83.90 %) at 220 kV/cm. A single layer ceramic capacitor (SLCC) was also prepared by the tape casting technique for multilayer ceramic capacitors (MLCCs) to further enhance the energy storage performance. The recoverable energy storage capacity is increased to 4.52 J/cm3 and the efficiency is 70.02 % at 460 kV/cm. Moreover, it still has a relatively stable energy storage performance after 105 cycles of charge and discharge. This sample has exhibited outstanding energy storage performance, fatigue resistance, and charge/discharge performance and has great potential value in practical applications. [ABSTRACT FROM AUTHOR]

Controlling the texture of tantalum sheets is of critical importance to fabricate good sputtering targets. In the present study two tantalum sheets were produced by clock rolling to 70% thickness reduction in 1 or 2 cycles. The results show that the stored energy and grain subdivision within the {111} grains {<111>//normal direction (ND)} after 1 cycle are significantly higher than those after 2 cycles, leading to fast recrystallization kinetics and strong {111} recrystallized texture upon annealing. Simulations with Taylor model indicate that shear strain occurred on more slip systems in the 2-cycle sample, which could explain the formation of cell blocks in {111} grains. Image 1 • Two sheets were produced by 135° clock rolling to same reduction in 1 or 2 cycles. • Different deformation substructures existed in the {111} grains in the two samples. • The recrystallization rate in the {111} grains in the 1-cycle sheet was much faster. • Taylor model was adopted to clarify the difference in deformation behavior. [ABSTRACT FROM AUTHOR]

[Display omitted] • The stored energy evolution tends to some asymptotic value close to damage. • Analysis of the AE signal revealed two different clusters during crack propagation. • Heat dissipation correlates with AE signal cluster probably associated with crack growth. • The stored energy is sensitive to AE signal cluster probably associated with twin density. The aim of this work was to investigate the correlation between structural, acoustic emission and thermal characteristics of the fatigue crack growth in titanium alloys. Cluster analysis of the acoustic emission signals revealed two different types of signals recorded during the development of a fatigue crack. It has been shown experimentally that the evolution of the stored energy tends to an asymptotic value at the final stage of fatigue crack growth and it correlates with the intensification of the twinning process in titanium alloy Ti Grade 2. A correlation was assumed between the stages of change in the heat flux, the cumulative energy of the first cluster of AE signals and the crack length. [ABSTRACT FROM AUTHOR]

The energy stored in the crystallographic defects in nanocrystalline Ni-Mo alloy films was determined experimentally by differential scanning calorimetry (DSC) and compared with the calculated values. Two Ni-Mo layers with low (∼0.4 at.%) and high (∼5.3 at.%) Mo contents were processed by electrodeposition. It was revealed that the majority of the heat released during DSC (∼77%) was related to the grain boundaries. It was also found that the increase of Mo content from 0.4 to 5.3 at.% yielded an enhancement of the stored energy with a factor of about two. The measured and the calculated stored energies were compared with the values obtained for ultrafine-grained Ni-Mo alloys with similar compositions but processed by severe plastic deformation (SPD). It was revealed that in the SPD-processed samples there was a considerable contribution of vacancies to stored energy while their effect in the electrodeposited layers was lower. • The stored energy in Ni-Mo films was calculated and compared with calorimetry results. • About 77% of the stored energy was caused by grain boundaries. • Higher Mo content yielded larger stored energy with unchanged fraction of GB energy. • The specific GB energy in electroplated Ni-Mo alloys was estimated as 0.5–0.7 J/m2. • The electrodeposited films contained less vacancies than the SPD-processed samples. [ABSTRACT FROM AUTHOR]

Effects of low clock rolling passes on through-thickness deformation and recrystallization behavior of the Ta sheet have been investigated. The clock-rolled samples with one cycle (8 passes) were systematically examined under different thickness layers. X-ray diffraction (XRD) and X-ray diffraction line profile analysis (XLPA) showed that the extremely inhomogeneous texture evolution generated and the bulk stored energy existed in the through-thickness clock-rolled Ta sheet after 8 passes. The electron backscatter diffraction (EBSD) results revealed the misorientation of the grains in the deformed samples, indicating that grain subdivision in the surface and center layer was more serious than that in the quarter layer. High intensities misorientation indicates the presence of microshear bands in the surface and center layer. During annealing, the difference of the stored energy and the fragmentation of deformation microstructure along the thickness led to a heterogeneous driving force for the nucleation of the grains, resulting in subsequent different recrystallization rate in the different regions of the sample. Image 1 • Texture and stored energy along the thickness was uneven in the Ta with one cycle. • Schmid factor analysis was adopted to clarify the difference in deformation behavior. • The inconsistent recrystallization rate indicates the uneven deformation degree. [ABSTRACT FROM AUTHOR]

• Crystal plasticity modeling used to solve for SCS specimen fitting parameters. • Twin-dominated plasticity has a lower conversion of plastic work to heat in AZ31B. • Slip-dominated plasticity has a higher conversion of plastic work to heat in AZ31B. In this study the conversion of plastic work to heat of a hot-rolled magnesium alloy AZ31B is investigated using a mechanism-based approach. Shear-compression specimen loading orientations are selected to promote plastic deformation principally through either basal slip, combined pyramidal and prismatic slip, or extension twinning. Loading orientations were selected based on predictions from a crystal plasticity model. High strain-rate adiabatic deformation was accomplished using a compression Kolsky bar. During each experiment the deforming gauge section temperature rise is recorded using a single-point infra-red detector. From the specimen deformation, thermal measurements, and crystal plasticity calculations of mechanism activity, the conversion of plastic work to heat was inferred. Specimens where basal, prismatic, and pyramidal slip accounted for the majority of plastic deformation exhibited similar percentage of plastic work converted to heat. Specimens where extension twinning was highly active exhibited a comparatively lower fraction of plastic work converted to heat. [ABSTRACT FROM AUTHOR]

The investigation of new ceramics and ceramic composites to overcome the inadequacies of monolithic ceramics without using costly techniques and equipment is essential for developing ceramic armor components. The aim of the research was analyzing the mechanical properties (elastic modulus, flexural strength, and hardness) of Al 2 O 3 /1 vol% Ni nanocomposites with 5 vol% ZrO 2 or 1 vol% Cr 2 O 3 additives and estimating their performance by comparing with the pure Al 2 O 3 , Al 2 O 3 /ZrO 2 composite, and Al 2 O 3 /Cr 2 O 3 ceramic system for armor applications. The heterogeneous precipitation method was used to obtain nano-sized metal particles in the ceramic matrix for the Ni-containing compositions. Equibiaxial flexural tests were conducted for strength measurements and stored energy at failure was estimated by using the theoretical deflection of the cylindrical plate; also, post-failure total crack lengths were measured. Simultaneous addition of Ni and ZrO 2 on Al 2 O 3 matrix resulted in the highest hardness (25.5 ± 1.0 GPa) and flexural strength (367 ± 34 MPa) compared to other compositions because of the hardening effect of Ni and the grain boundary strengthening mechanism. Moreover, this composition showed the highest resistance to fragmentation as evidenced by the shortest crack length per stored energy at failure. Cr 2 O 3 addition also provided remarkable results related to the solid solution formation for both the pure Al 2 O 3 and Al 2 O 3 /Ni composites. By this comparative study, different compositions with high mechanical properties have been introduced as the potential candidates to be used in armor applications with static tests giving an indication about ballistic performance. [ABSTRACT FROM AUTHOR]

Abstract To overcome brittleness of bulk metallic glasses, great efforts have been devoted to optimizing BMGs′ plasticity under compressive, tensional or bending load. Yet, it is hardly found any work done to enhance torsional plasticity of BMGs. Herein, based on the different stored energy of BMGs determining diverse properties, we introduce the energy into Zr 54.46 Al 9.9 Ni 4.95 Cu 29.7 Pd 0.99 BMG by a high rheological rate forming method, leading to the higher microstructural heterogeneity, which is conducive to increase not only the plasticity (from 0.2% up to 1.56%) but also the ultimate strength from (990 MPa up to 1110 MPa) on the torsional deformation effectively. This work provides a new orientation to break through the brittleness of BMGs. [ABSTRACT FROM AUTHOR]

Highlights • Stored energy of the samples was calculated by the EBSD images. • The stored energy affected the run-in period and the wear rate in pure Ti. • The friction stir processed pure Ti with appropriate stored energy exhibited good wear resistance. Abstract The friction stir processed pure Ti was annealed at 550 °C with various annealing times. Dry sliding wear tests on friction stir processed and as-annealed pure Ti were performed at room temperature. Friction coefficient and wear rate of the alloys were measured. The results showed that the friction stir processed pure Ti with high hardness revealed lower wear resistance than as-annealed samples. The stored energy of the samples before and after annealing treatment were calculated. The relationship between work hardening and wear resistance of pure Ti was discussed. The run-in period increased as the stored energy in the pure Ti decreased. The fine-grained pure Ti with 400 kJ/m3 low angle grain boundaries stored energy exhibited the lowest wear rate. The wear mechanism of fine-grained pure Ti changed from fatigue wear and abrasive wear to adhesive wear after annealing treatment. [ABSTRACT FROM AUTHOR]

Abstract This work experimentally investigated photothermal conversion behavior of Gold/water and MWCNT/water nanofluids at different volumetric concentrations (0.0001–0.004% and 0.0001–0.03%, respectively) in a direct absorption solar collector (DASC). The experiments were conducted for ~10 h outdoor on each test day, without interruptions. The results show that the tested nanofluids have excellent photothermal conversion capability even under very low concentrations. Specific absorption rate (SAR) presented an exponential decay with increasing volumetric concentration of nanoparticles in the sample while both the total energy stored by the fluid sample during the heating period and the stored energy ratio (SER) increased with the increase in nanoparticles concentration. The results indicate the existence of an "optimal" volumetric concentration, above which further nanoparticle addition becomes indifferent or infeasible. This optimal nanoparticle volumetric concentration was found to be 0.002% for the gold nanofluid and 0.001% for the MWCNT samples for the setup used in this work. Highlights • Comparative study of photothermal conversion using two nanomaterials (gold nanoparticles, MWCNT) under realistic conditions. • Several volumetric concentrations were tested and an optimal concentration for future applications was proposed. • MWCNT samples presented remarkable improvement of photothermal conversion efficiency and preserved homogeneity after testing. • Au-water samples presented evidences of degradation after several hours of solar exposure. [ABSTRACT FROM AUTHOR]

The effect of the scanning speed on the fatigue behavior of Laser Powder Bed Fusion (LPBF)-fabricated 316L steel is investigated in this paper. To this end, fatigue limits of specimen manufactured by different scanning speeds are determined by the self-heating approach. EBSD experiments and relative density measurements are carried out to characterize the microstructure and porosity. To analyze the influence of scanning speed on the microstructure (grain morphology, texture, dislocation density and stored energy) and fatigue property, a dislocation-density, crystal plasticity and stored energy-based fatigue model is developed. The inverse optimization method is combined with EBSD experiments and uniaxial tension experiments to identify the model parameters. The experimental results show a critical scanning speed, below which the fatigue limit stays almost unchanged and decreases drastically while the scanning speed is increased beyond. Furthermore, the simulation results show that the predicted fatigue limits correspond well to the experimental fatigue ones. From experimental and numerical results, it is deduced that the critical stored energy density and maximum temperature variation are functions of the porosity and can be used to differentiate the types of fatigue: microstructure-dominated or defect-dominated. This article provides new insights which can be further used in the optimization of fatigue behavior of LPBF 316L steel with respect to the scanning speed. [ABSTRACT FROM AUTHOR]

This research work is an attempt to understand the effect of stored strain energy heterogeneity over macro-scale, induced during interrupted annealing treatment, on the micro structural evolution in a heavily cold rolled AISI 304L austenitic stainless steel. The cold rolled AISI 304L stainless steel (SS) samples were subjected to different annealing treatments. The microstructures obtained after each annealing treatment were characterized using optical and electron microscopy techniques. Further, an attempt was made to estimate the stored strain energy by a novel approach of micro hardness measurement both over small scale (area 3600 μm 2 ) and large scale (area ~0.25 mm 2 ). The stored strain energy was determined using hardness values. Using these data, spatial stored strain energy distribution contour maps were created. They were, in turn, used to characterize the local softening behavior both at micro and macro-scale levels after each interrupted annealing treatment. The results showed that, interrupted annealing treatment induces increased stored strain energy heterogeneity after each annealing interruptions. Also, it was possible to determine recrystallization kinetics of the material using stored strain energy map, which helps in designing annealing cycles for achieving ultrafine grained microstructure. [ABSTRACT FROM AUTHOR]

This work proposes thermodynamic model for stored energy evolution in metals within the internal variable approach. It is assumed that stored energy is a function of strain-type variable (structural strain) while dissipated energy is a function of plastic strain. Constitutive equations are derived for one-dimensional case and then generalized to the three-dimensional one. The proposed model is based on the introduction of two independent dissipation potentials with the corresponding multipliers for plastic strain and structural strain. Efficiency of the proposed model is demonstrated by two numerical examples. The first example is a simulation of the energy balance in the process of quasi-static deformation of Ti-1Al-1Mn alloy. The second example is modeling of the fatigue crack growth rate in Ti-1Al-1Mn alloy on the base of the consideration of energy balance at the crack tip. Numerical results have good agreement with the original experimental data. [ABSTRACT FROM AUTHOR]

The hysteresis observed in the mechanical response of filled rubbers is classically assumed to be due to viscosity. In this study, a complete energy balance is carried out during cyclic deformation of a filled acrylonitrile-butadiene rubber. Results show that for the studied material, viscosity is not the preponderant contribution to the hysteresis loop: the mechanical energy brought to the material is not entirely dissipated into heat but a contrario is mainly used by the material to change its microstructure. Moreover, no significant hysteresis loop is observed in the unfilled material. Hence, the filler network stores elastic energy during its deformation, leading to a change in the internal energy. The higher the stretch applied, the higher the relative stored energy, but the higher the stretch rate applied, the lower the relative stored energy in the filler network. This has been evidenced by defining a ratio γ se in terms of energy. As hysteresis loop in rubbers does not systematically mean that intrinsic dissipation is produced, predicting changes in temperature, and consequently the self-heating, is not possible from the mechanical response only. To conclude, this study presents the first estimation of stored energy in a filled rubber. [ABSTRACT FROM AUTHOR]

• Strain localizations (SLs) were observed preferentially in Copper-type grains in the CR Cu-Fe-P specimens. • Self-annealing at room temperature was observed at the deformed GBs and at SLs in the CR specimens. • TEM and TKD confirms that DSRX and CSRX were responsible for the self-annealing phenomena in the CR specimens. • CPFEM simulation was showing the nearby predictions for average grain size (GS avg) and texture fraction. • Activation of single-slip system in the Copper and S oriented grains was the primary cause of SLs formations. Deformation of Cu-Fe-P alloys at cryogenic temperature (CT) leads to the evolution of a complex microstructure, which includes deformed and recrystallized grains, strain localizations (SLs), and heterogeneous deformation. In this study, specimens of Cu-Fe-P alloy were subjected to cryogenic rolling (CR) at reduction ratios (RR) of 20, 40, 60, and 80%. The microstructural evolution of the CR specimens was characterized using electron back-scattered diffraction (EBSD) and high-resolution transmission electron microscopy (HR-TEM). Severely deformed CR specimens showed SLs, which formed predominantly in the Copper and S oriented grains. After deformation, the CR specimens exhibited self-annealing behavior, which is also referred to as static recrystallization (SRX). Self-annealing at room temperature (RT) caused grain nucleation at the deformed grain boundaries (GBs) and at the SLs. The nucleation of new grains was attributed to both discontinuous SRX (DSRX) and continuous SRX (CSRX) phenomena. The characteristics of DSRX and CSRX grains were analyzed based on transmission Kikuchi diffraction (TKD) and HR-TEM investigations. DSRX grains were surrounded by high-angle GBs, whereas CSRX grains showed sub-boundaries with no dislocations inside. The as-received Cu-Fe-P specimen showed a weak plane-strain texture that intensity increased with an increase in the RR. The CR-80 specimen showed the highest-intensity for plane-strain texture components. SRX at the SLs showed preferential formations of Copper, Brass and S-nucleated grains in the CR-80 specimen. In this study, crystal plasticity finite element method (CPFEM) was used to calculate the stored energy, relative slip activity and texture fractions for the CR specimens. Copper and S oriented grains showed the occurrence of predominant single-slip systems near the severely deformed regions which was the primary cause of SLs formation. [Display omitted] [ABSTRACT FROM AUTHOR]

In semiconductor integrated circuits, the orientation dependence of the stored energy and texture distribution uniformity of sputtering tantalum targets are critical to the properties of the deposited films which block the diffusion of Cu atoms into the storage cell Si. In this paper, the effect of heating rate on the recrystallization behavior was investigated with the aid of a differential scanning calorimeter (DSC). In addition, the texture and stored energy of deformed tantalum targets with different heat treatments along the thickness direction were characterized using electron backscatter diffraction (EBSD). The results show that the initial temperature of recrystallization rises but the temperature range reduces with the increase of the heating rates. The stored energy of deformed tantalum targets presents various orientation dependencies in different thickness layers. During the heating process, the stored energy difference among the grains with different orientations decreases, but the maximum difference of stored energy in different thicknesses increases inversely. The content of {101} oriented grains increases as the temperature increases, while the content changes of {111} and {001} present a waveform with an opposite trend. • The orientation dependence of the stored energy varies in different layers. • The content of {111} and {001} grains with heating changes in a waveform. • Growth mechanisms of differently oriented sub-grains are different. • {001} recrystallized grains nucleate at grain boundaries of {111} deformed matrix. [ABSTRACT FROM AUTHOR]

Tantalum samples were dynamically deformed at liquid nitrogen (LN) temperature to obtain one pass (LN-DPD-1pass) and three pass LN-dynamic plastic deformation (LN-DPD-3pass) samples, and Ta was also dynamically loaded at room temperature (RT-DPD) for comparison. Results showed that although all the three DPD samples are essentially formed by {100} and {111} grains, the LN-DPD-3pass sample is significantly more severely fragmented. The low-angle grain boundaries are fairly uniformly distributed indicating a high homogeneity of the deformed microstructure. Meanwhile, the proportion of random texture in LN-DPD-3pass sample is higher as compared to the other two samples due to the rotation of dynamic recrystallization grains during DPD. Uniform deformation structure and similar stored energy of the deformed grains lead to the formation of excellent microstructure in the annealed LN-DPD-3pass samples. • The orientation dependence of deformation behavior is significantly weakened by decreasing the DPD temperature. • S R results indicate that the LN-DPD sample is more likely to activate multiple slips than the RT-DPD sample. • The annealed LN-DPD-3pass sample shows an excellent microstructure with fine grain size and uniform texture. [ABSTRACT FROM AUTHOR]

The evolution of stored energy associated with Brass {110}<112>, Copper {112}<111>, S {231}<346> and Cube {001}<100> texture components of Fe-36Ni (wt.%) Invar alloy after accumulative roll-bonding (ARB) processing up to 6 cycles was investigated using two methods: Neutron Diffraction peak broadening analysis and Kernel Average Misorientation (KAM) in an electron backscatter diffraction (EBSD). Both methods evidence the stored energy evolution variation as E Copper > E S > E Brass > E Cube . The stored energy increases first with strain up to 3 cycles and then decreases and then slightly rises up again between 4 and 6 cycles but with a trend towards stabilization. The overall evolution of the stored energy versus strain was related to the dislocation density and substructure evolution as well as recovery process. The small increase of the stored energy at high deformation levels is due to the production of new dislocations. Comparisons between results obtained with the two methods and with Dillamore approach show that Geometrically Necessary Dislocations (GND) dislocations in the cells/sub-grains walls are the principal contributor to the stored energy of the alloy. [ABSTRACT FROM AUTHOR]

By using the infrared thermographic method, a non-destructive testing technique was applied to detect the surface-temperature evolution of solid propellants during strain-control fatigue tests within finite cycles. When the applied strains were below the viscoelastic limit, two stages of temperature variation were observed before the initiation of macroscopic cracks: an initial temperature-increase stage, and a steady temperature state. Thermodynamic analysis was carried out and a method was developed to allow the acquisition of stored energy at different stages of cyclic loading, which can reflect the material damage on the macroscopic scale. In addition, temperature localization during fatigue was observed, which implied the occurrence of damage accumulation and crack propagation. The results reveal that the cyclic-loading induced temperature increase of solid propellants during the fatigue process has a significant effect on solid rocket motors in a transportation or storage state. [ABSTRACT FROM AUTHOR]

This study investigates the mechanistic approach to evaluate total stored energy consisting of damage energy (due to voids and microcracks) and deformation energy (due to dislocations). Thermal data obtained by online IRT technique have been employed for this evaluation. The deformation energy is estimated through EBSD analysis. Subsequently, the damage and deformation induced by creep and fatigue have been modeled as functions of applied stress and cumulative plastic strain, individually. By using the data of experimental creep stress and fatigue strain for each creep-fatigue cycle, the contributions of creep and fatigue damage energies have been estimated for creep-fatigue interaction. New fatigue and creep damage parameters have been proposed based on the damage mechanics concepts. Different regimes have been identified and explained with creep and fatigue damage evolution curves. The present approach has also been extended to characterize incremental creep-fatigue interactions. [ABSTRACT FROM AUTHOR]

Cylindrical specimens of as-extruded AA2099 Al-Li alloy are uniaxially compressed at temperatures ranging from 360 °C to 520 °C and strain rates ranging from 0.001 s −1 to 10 s −1 . Processing map of these specimens was established. Electron backscatter diffraction (EBSD) measurements were performed for specimens deformed under various conditions to probe their microstructures and restoration mechanisms. Stored energies in various specimens are calculated based on statistics of low angle boundaries via EBSD data. The remarkable decrement of stored energy and misorientation characteristics reveal that dynamic recrystallization (DRX) happens at 480–520 °C and 0.001–0.1 s −1 . Obvious DRX nucleation further suggests that this process should be classified to discontinuous dynamic recrystallization (DDRX). Stored energies in various specimens strongly affect the extents of dynamic recovery and dynamic recrystallization. By systemically considering the processing map and restoration behaviours of the specimens, the dynamic recrystallization regimes and the central high- η regimes are determined to correspond to preferable thermo-mechanical processing parameters for the as-extruded AA2099 Al-Li alloy. [ABSTRACT FROM AUTHOR]

In the present study an attempt has been made to understand the high strain hardening in austenitic low-density steel using two full field measurements of temperature and strain on the sample during tensile deformation. Based on these measurements' evolution of energy storage during deformation was calculated. High energy storage has been attributed to the interaction between dislocation groups belonging to different slip bands and destruction of short-range order (SRO) clusters. This in turn, dictates the range of the elastic stress field of slip bands. Furthermore, weak deformation heterogeneity ensued just after yield and continued with a fixed strain pattern up to facture. This did not result in macroscopic instability but manifested as microstructural heterogeneity in the form of micro-band and nano twins at later stages of deformation. A mathematical model of energy storage based on dislocation entrapment is discussed. [ABSTRACT FROM AUTHOR]

In this paper, a fine distinction between the role of strain-paths on the evolution of mechanical properties has been reported. Commercially pure (CP) titanium plates were subjected to hot rolling of 90% reduction in thickness through different strain-paths such as unidirectional rolling (UDR), multistep cross-rolling (MSCR) and reverse-rolling (RR). It was observed that the sample rolled through RR had higher mechanical properties (both yield strength and ductility) followed by the samples rolled through MSCR and UDR respectively. It was further observed that the RR sample had higher stored energy followed by MSCR and UDR samples which eventually controls the evolution of microstructure and hence defines the mechanical properties. [ABSTRACT FROM AUTHOR]

In the scaled-down test facilities that simulate the accident transient process of the prototype nuclear power plant, the stored energy release in the metal structures has an important influence on the accuracy and effectiveness of the experimental data. Three methods of stored energy analysis are developed, and the mechanism behind stored energy distortion in the test facilities is revealed. Moreover, the application of stored energy analysis is demonstrated for the ACME test facility newly built in China. The results show that the similarity requirements of three methods analyzing the stored energy release decrease gradually. The physical mechanism of stored energy release process can be characterized by the dimensionless numbers including Stanton number, Fourier number and Biot number. Under the premise of satisfying the overall similarity of natural circulation, the stored energy release process in the scale-down test facilities cannot maintain exact similarity. The results of the application of stored energy analysis illustrate that both the transient release process and integral total stored energy of the reactor pressure vessel wall of CAP1400 power plant can be well reproduced in the ACME test facility. [ABSTRACT FROM AUTHOR]

Grains with γ-fiber texture (〈111〉 direction // normal direction (ND)) and θ-fiber texture (〈100〉 direction // ND) show different subdivision behaviors during unidirectional rolling, which leads to orientation-dependent stored energy. This orientation dependence in tantalum can be largely alleviated by a novel approach named 135° clock rolling, which is attributed to two reasons. One is that the clock rolling can weaken the micro-shear bands and destroy the parallel dislocation boundaries in γ-fiber grains, thus reducing their stored energies; and the other is that the clock rolling changes the stability of θ-fiber orientations and introduces plenty of “veins” into θ-fiber grains, thereby increasing corresponding stored energies. Therefore, 135° clock rolling narrows the stored energy difference between these two types of grains, which is beneficial for homogenizing the annealing microstructure of tantalum. [ABSTRACT FROM AUTHOR]

Coatings are applied to titanium alloys to prolong the life of the components by improving the high temperature oxidation and corrosion resistance. The coating thickness needs to be optimized depending upon the service conditions. The coating thickness can potentially affect the mechanical properties of the substrate alloy. In the present study, the effect of variation in the coating thickness on the deformation behavior of a near-α titanium alloy coated with Al 3 Ti aluminide has been studied. Infrared thermography technique has been used to monitor the local heat evolution along the gauge portion of uncoated and coated specimens during tensile deformation. The technique has been used to measure the dissipated heat and to monitor the changes in the stored energy during tensile deformation. The presence of coating led to only marginal variations in strength although it reduced the alloy ductility significantly. The coated specimens failed by propagation of cracks from the coating to the substrate material. It is observed that several cracks penetrate into the substrate alloy and the unstable propagation of these cracks led to failure of the specimen. This study also shows that the localized heat evolution during the crack propagation process can be effectively used as a parameter for studying the in-homogeneous deformation and fracture process typical in coated materials. [ABSTRACT FROM AUTHOR]

To improve the performances of high-temperature superconducting (HTS) coils, it is necessary to store more energy within a shorter HTS tape length and to reduce leakage magnetic fields. To attain these goals, we need to increase the critical current of the coil. The critical currents and n -values of the HTS tape generally depend on the magnitudes and angles of the applied magnetic field. Therefore, we calculated the transport current performances of HTS coils with anisotropic properties. In general, anisotropy generates relatively large electric fields at the coil edges, limiting the transport current performances of the coil. To solve this problem, we proposed a new symmetric, lattice shaped HTS coil cross sections. The coil assembly consists of small ring-shaped coils of rectangular cross section forming pairs of Helmholtz coils. As a result, the angle between the magnetic field and tape and electric fields decreased, resulting in an increase in the critical current of the coil. Through this optimization, the stored energy increased 2.2 times compared with a normal rectangular solenoid coil with the same HTS tape length. Furthermore, the leakage magnetic field was substantially reduced. [ABSTRACT FROM AUTHOR]

Pumped hydro energy storage (PHS) currently is the only electricity grid storage technology with substantial deployment throughout the world, representing over 99% of storage capacity, but other storage technologies such as batteries are increasingly finding application. In Europe, the implementation of storage systems is expected to increase because of the integration of intermittent, nondispatchable renewable energy sources. Nevertheless, there is no overview available of the power and energy ratings of large-scale stationary storage at the supranational level. In the absence of officially collected statistics on energy capacity, publicly available information is collected from storage owners, freely accessible databases, scientific articles, reports, brochures and government websites. The status of PHS and other large-scale storage technologies in the EU-28 countries, supplemented by Norway and Switzerland, is presented. First, this paper defines a measure of energy storage capacity, to allow comparison of pumped hydro storage plants with other storage technologies. Next, a set of technical parameters of current large-scale storage plants is presented, as well as an overview of planned storage projects. The estimate of PHS power ratings in the EU-28 exceeds previous estimates, with a total of 160 plants and 45.283 GW rated power in turbine mode and a full cycle storage capacity of 602 GWh. When adding Norway and Switzerland, a total of 188 operational PHS plants is shown with 1313 GWh. The data is used to obtain EU-wide discharge curves and national indicators of utilization and significance. [ABSTRACT FROM AUTHOR]

• Improving quality of power supply in remote areas and reducing burden on power grid. • A micro off-grid power supply system with peak load shifting is designed and analyzed. • Multi-perspective evaluation is carried out. • The payback time is reduced by 42% to 4.00 years in the case presented. Nowadays, the proportion of thermal power generation is still large, the waste of electricity will lead to more environmental pollution. With the continuous increase in electricity demand, how to improve the quality of power supply, reduce transmission loss and ease the burden of power grid are urgent problems to be solved. The combination of fuel cell and energy storage technology could be a good solution. In this article, a new off-grid system with peak load shifting function is proposed to solve problems of power supply in remote regions. This combined system consists of a solid oxide fuel cell, a regenerative Brayton cycle, an organic Rankine cycle and a compressed-air energy storage system. By rational utilization of waste heat in exhaust gas, the cascade utilization of energy can be realized. The results indicate that the fuel cell-waste heat recovery system can achieve higher thermal efficiency and exergy efficiency, with an improvement of 6.69% and 6.46%, respectively. The application of compressed-air energy storage system not only makes the system have the functions of energy storage and peak regulation, but also improves the economic performance. The system reaches a minimum payback time of 4 years in the case presented. In conclusion, this new combined system is clean, efficient and economical, which can provide a good solution for power supply in coteaux, suburbs and islands. [ABSTRACT FROM AUTHOR]

• Microstructural and crystallographic texture evolution in the RTR and CR ETP copper were investigated systematically. • CR-processed specimens showed higher hardening and softening rate than RTR-processed specimens. • SRX at room temperature was the main softening phenomena observed in the severely deformed specimens. • DSRX and CSRX were responsible for the nucleation of small grains at room temperature in the severely deformed RTR and CR-processed specimens. • Time-dependent decay in the hardness values for the RTR and CR specimens, attributed to the SRV and SRX. The present study addresses the evolution of microstructural and crystallographic texture in room-temperature-rolled (RTR) and cryogenic-rolled (CR) electrolytic tough-pitch (ETP) copper. Copper specimens were subjected to 20, 40, 60, and 80% reductions via RTR and CR processing. The microstructure evolution of the severely deformed RTR and CR specimens revealed deformed and recrystallized grains. Static recrystallization (SRX) at room temperature (RT) was observed in the severely deformed RTR and CR specimens. Both discontinuous SRX (DSRX) and continuous SRX (CSRX) were responsible for the nucleation of small grains at RT. Particle-stimulated nucleation (PSN) was also responsible for small-grain formations around the Cu 2 O particles. The initial ETP copper specimen showed a weak texture whose intensity increased after the RTR and CR deformation. The texture intensity of the severely deformed specimens was affected by both deformation and the SRX phenomena. The CR specimens showed texture that was stronger than that of the RTR specimens up to the point of an intermediate reduction (60%), whereas at higher deformation (80%), the RTR specimens showed stronger texture intensity compared with that of the CR specimens. The texture weakening in the CR80 specimen was due to the formation of strain localizations (SLs) and to the nucleation at SLs. Large amounts of stored energy and SL formation in severely deformed CR specimens led to a different recrystallization texture compared with that of RTR specimens. A Cube component was dominant in the RTR80, whereas Goss, Copper and S components were observed in the CR80 specimen for SRX grains. The CR specimen showed a relatively high hardness value compared with the RTR specimen. Time-dependent decay in the hardness values for both the RTR and the CR specimens were attributed to room-temperature recovery (SRV) and recrystallization (SRX). [ABSTRACT FROM AUTHOR]

In this contribution, the phenomenon of work hardening is studied as a function of the nature of dislocation evolution with change in the level of deformation for commercially available 1050 Al alloy. To investigate the nature of dislocations in the cold-rolled aluminum alloy, total dislocation density was calculated using the indentation technique as well as by implementing two numerical approaches. For estimation of a statistically representative value of geometrically necessary dislocations (GND), electron backscattering diffraction measurements were performed over a large area (~ 0.5 mm2). The GND density of deformed samples was quantified by the implementation of a modified kernel average misorientation technique as well as by using Nye's dislocation density tensor for corresponding lattice curvature. The values of statistically stored dislocations (SSD) are obtained based on the assessment of the total dislocation density and GND values after different straining levels. The study provides both qualitative and quantitative illustrations of the mechanism of dislocation multiplication as thickness reduction increases, thereby, increasing the hardness of the samples. The results obtained reveal that the hardening of rolled materials is majorly governed by the SSD density at lower deformation. However, as the deformation level approaches the value of ~0.4, the density of GNDs rises and its contribution becomes significantly accountable for the strain hardening of the material. On the other hand, it has been observed that at lower straining levels the generated GNDs are trapped at grain boundaries and have a high contribution towards forest dislocations but with an increase of strain, the GNDs have a tendency to contribute nearly equally to mobile and forest dislocations. The estimated stored energies for samples subjected to rolling reduction ranging between 5.3 and 76% tend to change between the 5.6 kJ/m3 and 343.3 kJ/m3. • The total dislocation density and the amount of both GNDs and SSDs were estimated by mean of indentation and EBSD. • The quantification of GND density has been analyzed by two different techniques. • The contribution of GNDs in mobile and forest counterparts of total dislocation density has been revealed. • The stored energy was derived for a wide range of straining levels. [ABSTRACT FROM AUTHOR]

This paper aims at studying the ratio of plastic work converted to heat, β (Taylor and Quinney, 1934) in pressure vessel steels used in VVER-440 energetic reactors by an inverse-experimental and computational analysis. The experiments were performed with different strain rates on a thermal-mechanical testing machine from DSI (model GLEEBLE-3800). Because of the magnitude of strain rate during the experiments it cannot be modelled as an adiabatic process, also the heat transfer during the tests has to be taken into account. Analytical model was carried out to account for the conduction, convection and radiation heat losses that occur during the tests. A thermodynamically based thermo-elasto-plastic model is used to describe both the stress–strain behavior and temperature evolution in these steels under monotonic uniaxial loading. The governing equation system of thermo-elasto-plasticity was implemented in MATLAB software. It is found that β is always smaller for compression than that of tension. The results for 15Ch2MFA (bainitic structure with fine grains) show a rather strong dependence on strain rate, whereas 08Ch18N10T (austenitic structure with coarse grains) is practically independent. The results obtained by the investigation correspond to the literature. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study of a new designed Trombe wall, which is a part of the southern wall of a test room, in terms of energy performance and heating comfort during winter operation for Yazd city (Iran) desert climate. The area of the Trombe wall is 50% of that of the southern wall of the test room. Hence, it occupies less space and reduces the implementation costs. Contrary to the traditional Trombe walls in which the absorber receives solar radiation from one direction, this innovative design enables the absorber to receive solar radiation from three directions (East, South and West), therefore, the absorbing surface of the wall is subject to the solar irradiation during the all day time (from sunrise to sunset). The experimental results revealed that the range of room temperature on the coldest winter days and weeks in Yazd is kept within 15–30 °C, and this implies that the present Trombe wall design is able to provide a comfortable indoor temperature with lower difference between the maximum and minimum temperatures due to the increased stored energy of the Trombe wall. Furthermore, the present innovative design of the Trombe wall channel causes the absorber temperature to reach around 47 °C on the coldest winter days, indicating the highest possible solar intensity received by the absorber. Analysis of the hourly stored energy of the Trombe wall reveals that the more solar intensity leads to the more energy absorption and the higher Trombe wall back surface temperature, which in turn causes the hourly stored energy to reach to a maximum of 5800 kJ/h in February. [ABSTRACT FROM AUTHOR]

The microstructural evolution of a cold-rolled steel 0.1C–5Mn was characterized by SEM and EBSD, and the α → γ phase transformation of the steel was determined by differential scanning calorimetry (DSC) upon heating. The retained austenite fraction and the dislocation density were examined by XRD. Based on the DSC data, the Kissinger׳s method was used to calculate the activation energy of the cold rolled steel. The activation energy of 363–824 kJ/mol suggested a sluggish phase transformation during the heating process and it showed an increase trend with the increase of thickness reduction which was affected by the density of the dislocation and the drag effect by the solute Mn. The stored energy (14–30 J/g) was associated with energy released from the α → γ transformation during the heating process. Based on the effects of temperature on the phase transformation behavior, the cold rolled medium-Mn steel with different thickness reductions were annealed at the onset phase transformation temperature with 5 min and 6 h, which results in a very good combination strength and ductility. [ABSTRACT FROM AUTHOR]

Nickel-base superalloy, Waspaloy, was linear friction welded (LFWed) under different axial shortening conditions of 2.0, 3.4, and 4.6 mm. The tensile properties and microhardness of the weldments were investigated in the as-LFWed condition and compared with those in the post-weld heat treated (PWHTed) condition. Mechanical properties were related to microstructures following examination by optical microscopy, high resolution scanning electron microscopy, and electron backscatter diffraction (EBSD). Analyses of the EBSD results in terms of the misorientation angle distribution, which represents the stored energy, were performed. In the as-LFWed condition, the yield strength (YS) and ultimate tensile strength (UTS) increased with axial shortening due to greater expulsion of the softened interfacial material toward the periphery as flash. In contrast, with increasing axial shortening the total elongation initially remained constant and then decreased. This was also related to the expulsion of the softened interfacial material into the bifurcated flash. Extensive dissolution of the strengthening phase ( γ′ ) in the weld area during linear friction welding (LFW) contributed to the lower YS and UTS in the as-welded condition compared to the PWHTed condition where the γ′ particles were recovered. After performing post-weld heat treatment (PWHT), the total elongation improved due to the relaxation of stored energy and grain growth in the thermomechanically affected zone (TMAZ). [ABSTRACT FROM AUTHOR]

During the deformation of low carbon steel by cold-rolling, dislocations are created and stored in grains depending on local crystallographic orientation, deformation, and deformation gradient. Orientation dependent dislocation densities have been estimated from the broadening of X-ray diffraction lines measured on a synchrotron beamline. Different cold-rolling levels (from 30% to 95% thickness reduction) have been considered. It is shown that the present measurements are consistent with the hypothesis of the sole consideration of screw dislocations for the analysis of the data. The presented evolutions show that the dislocation density first increases within the α fiber (={hkl}<110>) and then within the γ fiber (={111}). A comparison with EBSD measurements is done and confirms that the storage of dislocations during the deformation process is orientation dependent and that this dependence is correlated to the cold-rolling level. If we assume that this dislocation density acts as a driving force during recrystallization, these observations can explain the fact that the recrystallization mechanisms are generally different after moderate or large strains. [ABSTRACT FROM AUTHOR]

The stored energy during deformation under different strains, strain rates and deformation temperatures was investigated in this paper. Thermal simulation compression and dynamic compression tests were carried out to obtain the deformed specimens with different strains, strain rates and deformation temperatures. By means of electron backscatter diffraction (EBSD) analysis, the stored energy per volume under different deformation conditions was measured. Then, the effects of strain, deformation temperature, and strain rate on the stored energy were analyzed. The increase of strain and strain rate and the decrease of temperature are conducive to the accumulation of stored energy. The correlations between the stored energy and microstructure parameters including grain and subgrain size were determined. The results show that the grain size is inversely proportional to the stored energy, while the subgrain size is inversely proportional to the square root of the stored energy. The hardening effect during plastic deformation was well described from the side of stored energy. The stress-strain relationship and hardening rate can be accurately predicted based on the evolution of stored energy. A convenient method for the acquisition of stored energy through hardness measurement was provided based on the relationship between hardness and stored energy. The proportion of the stored energy to the plastic work and its dependence on the deformation conditions were discussed. It is concluded that the stored energy can be a comprehensive quantity to connect and analyze the macro and micro behavior in the plastic deformation. • Explore the effects of deformation conditions on stored energy during deformation. • Discuss the relation among the stored energy, microstructure and hardening effect. • Analyze the hardening behavior from the side of stored energy. • Propose a method to obtain stored energy through hardness measurement. [ABSTRACT FROM AUTHOR]

This study attempts to comprehensively characterise the cutting process behaviour based on the stored energy field in the cutting deformation zones. Studying the cutting mechanism is difficult because the cutting process is accompanied by complex macro- and micro-phenomena. Therefore, it is proposed that the stored energy inside the deformed materials can be selected as the characterisation index of the cutting process behaviour including the stress, hardness, microstructure, and slip lines in the cutting deformation zones. The stored energy prediction model and constitutive model are established based on the hardening behaviour and microstructure evolution mechanism of the material. These models are then integrated into a finite element cutting model to obtain the stored energy field in the orthogonal cutting process. The simulation results are verified by combining transmission electron microscopy analysis and image quality method using electron backscatter diffraction technology. The relationships between the stored energy field and the distributions of the microstructure, stress and hardness are discussed. The results demonstrate that the subgrain size can be accurately predicted based on the stored energy. The distribution laws of the stress and hardness in the cutting deformation zones can be reflected by the stored energy field, and a convenient method for predicting the stored energy field by the hardness distribution is proposed and verified. Based on the aforementioned results, the formation mechanisms of the chips and the machined surface are analysed, and it is found that the slip lines can be sufficiently characterised by the gradients of the stored energy field. The cutting forces, chip thickness, and shear angle can be accurately predicted at different cutting speeds, indicating the reliability of the constitutive model. Moreover, the deformation characteristics of hardened zone are analysed and the thickness is estimated based on the stored energy field. [Display omitted] • Obtain stored energy evolution model by hardening behaviour and micro mechanisms. • Characterise cutting process behavior by stored energy field in cutting deformation zones. • Propose an experimental method to obtain stored energy field combining TEM and EBSD analysis. • Predict the stored energy field by hardness distribution of the chip roots. • Analyse the formation mechanisms of chips and machined surface based on stored energy field. [ABSTRACT FROM AUTHOR]

In the paper, tantalum (Ta) samples were processed with one pass (1-pass), two passes (2-pass) and three passes (3-pass) dynamic plastic deformation (DPD). The deformed and annealed microstructures were studied by using multiple characterization techniques, such as electron backscatter diffraction (EBSD) and X-ray diffraction (XRD). Results showed that the yield strength increases from 611.81 MPa at the first DPD to 1055.19 MPa at the third DPD and all samples reached a 70% reduction finally. The deformed samples are mainly composed of {111}(<111>//LD) and {100}(<100>//LD) grains, and the grains are arranged alternately. Meanwhile, numerous micro shear bands (MSBs) appear in {111} grains of the 1-pass sample. In contrast, they are rarely observed in 2-pass and 3-pass samples, and the distribution of low-angle grain boundaries (LAGBs) and kernel average misorientation (KAM) are more uniform than 1-pass samples. Compared with the 1-pass sample, the 3-pass sample exhibits lower geometrically necessary dislocations (GND) density differences between {111} and {100} grains. The relative Schmidt factor (S R) results indicate that the 2-pass and 3-pass sample is more likely to activate multiple slips than the 1-pass sample. The stored energy variance between {111} and {100} grains in deformed samples is significantly weakened after increasing DPD passes, resulting in that microstructure and texture homogeneity after annealing are improved. [ABSTRACT FROM AUTHOR]