Deformation Bands Research Articles

Topological and Petrophysical Analyses Across a Fault Zone Containing Deformation Bands

Topological and Petrophysical Analyses Across a Fault Zone Containing Deformation Bands

Seismic and outcrop-based 3D characterization of fault damage zones in sandstones, Rio do Peixe Basin, Brazil

Fault damage zones, composed of sub-seismic deformation structures, are difficult to detect using seismic data. Still, they can be related to fault throw, which is widely measured in the subsurface. This research employs a multiscale approach that integrates outcrop studies with seismic reflection data to investigate the attributes of fault damage zones affecting porous sandstones. We provide an in-depth understanding of the 3D fault zone volume, investigating correlations between geometric attributes of faults (width of damage zone, frequency of subsidiaries structures, and fault termination) in the outcrop and the fault throw in the subsurface, with insights from deformation mechanisms within the fault zone. The methods encompass 1D scanlines to constrain the damage zone width on the outcrop. At the same time, the subsurface analysis uses 3D seismic data, seismic attributes, and deep learning neural network (DNN) fault volumes to interpret fault geometries and quantify fault throw at different depths. Results show that the area presents a complex fault zone with multiple fault sets, deformation bands, and fracture corridors trending mainly NE-SW, NW-SE, and E-W. The integration of surface and subsurface fault data enabled the identification of two portions in each fault set outcropping at the fault tip for E-W/ESE-WNW-striking faults and the central part of the fault for NE-SW-striking faults. Faults with the greatest length do not outcrop with the largest damage zone width since they are outcropping the tip of the fault. The parallel faults overlap their damage zones, increasing the deformation zones in the affected sandstones. Fault throw and damage zone width present a positive correlation. This relation is affected by fault segments and subsidiary faults.

Subshell gaps and onsets of collectivity from proton and neutron pairing gap correlations

Throughout the nuclear chart, particle-hole correlations give rise to giant resonances and, together with the proton–neutron interaction, deformation and rotational bands. In order to shed light on many-body correlations in open-shell nuclei, I explore macroscopic properties that could manifest from the collective behaviour of protons and neutrons. Intuitively, the correlation of proton and neutron Cooper pairs can be inferred from the respective pairing gaps, that can precisely be extracted from the AME 2020 atomic mass evaluation through odd-even atomic mass differences. This work shows that the combination of large and close-lying proton and neutron pairing gaps is sensitive to onsets of collectivity and subshell gaps in superfluid nuclei, away from major shell closures. Trends of reduced transition probabilities or B(E2) values — which describe the collective overlap between the wave functions of initial and final nuclear states — are revealed in overall agreement with data. Specially interesting is the peak of collectivity in the tin isotopes at 110Sn, instead of at midshell, as expected by large-scale shell-model calculations; a situation that has astounded the nuclear physics community for quite some time.

Spatial distribution of remaining movable and non-movable oil fractions in a depleted Maastrichtian chalk reservoir, Danish North Sea: Implications for CO2 storage

Depleted oil and gas fields constitute potentially important storage sites for CO2 in the subsurface, but large-scale injection of supercritical (sc) CO2 in chalk has not yet been attempted. One of the risks is the adverse effect of the substantial amount of remaining oil in the chalk reservoirs on scCO2 injection. In order to counter an undesired effect on injectivity, a fundamental understanding of the spatial distribution and quantity of the movable, semi-movable, and non-movable oil, and solid bitumen/asphaltenes fractions of the remaining oil is critical. In this study a combination of organic geochemistry (gas chromatography of the saturated fraction and programmed pyrolysis), and reflected light microscopy was applied to evaluate and measure the spatial distribution, volume, and saturation of different oil fractions in a well-defined reservoir interval of a waterflooded Maastrichtian chalk reservoir in the Danish Central Graben, North Sea. A total of 127 samples from a slightly deviated vertical well and two ∼5 km-long horizontal wells from the Halfdan and Dan fields were analyzed. An original uneven distribution of oil saturation and composition or different production efficiency of different levels in the reservoir may account for variations in the total oil and oil fraction saturations. Gas chromatography shows that the solvent extractable oil is quite similar in composition, characterized by a dominance of polar compounds and a high content of asphaltenes. Extended slow heating (ESH) pyrolysis reveals that most of the remaining oil saturation consists of semi-movable oil and total non-movable oil (non-movable oil plus solid bitumen/asphaltenes). Reduced oil gravity values (API) are related to evaporation loss of the lightest hydrocarbon fraction during core storage and increase of the relative proportion of the heavier oil fractions by waterflooding during production. Microscopy disclosed three forms of oil: i) Patchy distributed lighter, movable oil showing a bluish fluorescence, ii) Brownish staining with a dark orange to brownish fluorescence, and iii) Dark brown non-fluorescing oil and black solid bitumen/asphaltenes occurring in microfossils and along deformation bands and stylolites, constituting the heavy non-movable oil fractions. There is a general correlation between bulk rock porosity and the total non-movable oil saturation. It thus appears that the heavy non-movable oil fractions preferentially occur in association with low-permeability heterogeneities within high-permeability stratigraphic intervals. These intervals appear to favor accumulation of non-movable oil and solid bitumen/asphaltenes and may carry a higher risk for impeding scCO2 flow.

Effect of Aggressive Anions on the Stress Corrosion Cracking of Stainless Steel in Hot Pressurized Alkaline Water

Abstract U-bend stress corrosion cracking (SCC) testing of low Cr ferritic (Type 409) and austenitic (Type 304L) stainless steel was conducted in a hot pressured alkaline water to study the effect of aggressive anions (Cl− and HS−) on the relative susceptibility. SCC was only observed in Type 304L when immersed in the solution that contained both aggressive anions. Critical factors were identified based on cross-section examination of the U-bends after exposure using complementary electron microscopy techniques. These factors include: (i) preferential oxidation of deformation bands (arising from cold working), (ii) Ni-S compound formation at the oxide/metal interface and (iii) S and Cl incorporation into the inward growing Cr-rich oxide. These critical factors were considered within an overall slip dissolution-type mechanism to account for the SCC observed.

Cell structure development during cyclic deformation of near-[001] and near-[011] copper single crystals

Dislocation cell structures significantly influence the fatigue failure process. Research on the cell structures in multiple-slip-oriented copper single crystals has focused primarily on the [1‾11] orientation, whereas formation mechanisms and development processes of cell structures in [001] and [011] copper single crystals remain unclear. Therefore, this study examines the dislocation structures of near-[001] and near-[011] copper single crystals under cyclic deformation at high strain amplitudes. The cyclic stress–strain curve of the [011] crystals showed a distinct plateau at plastic shear strain amplitudes ≤7.5 × 10−3. In the plateau region, the dislocation structures consisted of cell structures along the (111) primary slip plane and matrix wall structures. Furthermore, (111) cell structures were formed in the single-slip deformation bands (DBs). After the plateau region, several types of new DBs could be observed due to the activation of multiple-slip systems. Multiple-slip DBs have a higher degree of plastic strain concentration than single-slip DBs, leading to the preferential formation of cell structures. For the near-[001] crystals, (111) cell structures were uniformly formed throughout the matrix, without the formation of DBs. The formation mechanism of the (111) cell boundary was independent of the stress axis and resulted from the interaction between the primary and coplanar slip systems.

Effect of prefatigue-induced persistent slip bands on the strength-ductility match in -oriented Cu single crystals

To explore the effect of persistent slip bands (PSBs) formed during cyclic loading on the static mechanical behavior of materials, [1‾12]-oriented Cu single crystals are selected as target materials, and the tensile behavior of Cu single crystals prefatigued to the stress saturation stage at different plastic shear strain amplitudes (γpl) and the corresponding microstructures, surface deformation features and fracture morphologies are systematically studied. The results show that the formation of few soft PSB ladder-like structures in hard dislocation veins during prefatigue deformation at γpl = 3.7 × 10−4 below the plateau region of cyclic stress-strain (CSS) curve can promote a synchronous improvement of strength and ductility (SISD) compared with the unfatigued crystal. As γpl increases to a lower value of 9.0 × 10−4 within the plateau region, the strength and ductility reduce sharply compared with the case at γpl = 3.7 × 10−4 due to more concentrated plastic deformation caused by a high volume fraction of prefatigue-induced PSBs. With continuously increasing γpl to a higher value of 2.3 × 10−3 within the plateau region, non-uniform dislocation distribution in labyrinth structures and the short spacing between labyrinth walls as well as the fine dislocation cells formed during tension jointly give rise to a slight increase in strength and ductility compared with the crystal prefatigued at γpl = 9.0 × 10−4. As γpl is increased to the level beyond the plateau region, the ductility and ultimate tensile strength continuously increase, resulting from the co-existence of wider deformation bands and dense dislocation walls.

Failure investigation of an AISI 316L pipe of the flare system in an off-shore oil platform

The oil and gas industries have severe operations conditions, which impose several failures in off-shore equipment. The Flare System is a pipe designed to safely dispose of relieving hydrocarbon gases and liquids during start-up, operational upsets, emergency shutdown, and maintenance activities. This work reported the failure investigation in a pipe of a high-pressure flare system. The pipe has a diameter of 220 mm and 4 mm of thickness, and according to the equipment datasheet, it was made in AISI 316L stainless steel. Two cracks were detected during the previous non-destructive inspection. Those failures were repaired, but another crack was detected after some months. Chemical composition was investigated using optical emission spectroscopy and elemental analysis, and the results are compatible with AISI 316L steel. The microstructure observed by light optical and scanning electron microscopes shows an austenitic matrix with deformation bands. The microhardness measurements and the XRD analysis show the martensite formation in those deformation bands. The tensile properties are in accordance with the standards. The fracture surface was investigated using scanning electron microscopy, the results point to fatigue failure.

Anatomy of a 300-million-year old fjord in Namibia

Namibia is remarkable in terms of its network of approximately 300-million-year-old fjords, cut by Gondwanan glaciers at high palaeolatitudes during the Late Palaeozoic Ice Age (LPIA). A classic suite of structures is preserved on Proterozoic bedrock, including striations, roches moutonnées and other subglacial features within many of these palaeovalleys. Some palaeovalleys are plastered with comparatively thin diamictites (a few metres) of presumed subglacial origin, in turn capped by ice marginal delta successions (tens of metres). Close examination of deposits in the outer Orutanda Fjord palaeovalley reveals an architecture that shows departure from this trend. There, boulder-bearing diamictites pass laterally into highly contorted heterolithic successions comprising folded and faulted sandstones, siltstones and shales. Aerial imagery from UAVs in tandem with traditional field observations permits mapping of assemblages of soft-sediment deformation structures (tight to recumbent folds, deformation bands, faults, sheath folds) together with spatial mapping of the long-axis of boulders in diamictite. Collectively, this assemblage of structures points towards subglacial deformation, and hence an origin as a “deforming bed” beneath a glacier. Whilst several open questions remain regarding the precise deformation mechanisms, the concept of glacial re-advances into a deeply incised palaeovalley is proposed, by direct analogy to similar stratigraphic architectures in the LPIA record of South America.

Achieving high strength in Mg-Gd-Ag-Zr alloy through heterogeneous microstructure with multimodal grain structure and hierarchical precipitates

The development of high-strength Magnesium (Mg) alloys is a key research focus due to their relatively low strength compared to other structural metals. In this paper, a high-strength Mg-13.4Gd-2.2Ag-0.4Zr wt% alloy is achieved by carefully designing a multimodal grain structure combined with hierarchical precipitates, using a processing route of hot rolling followed by aging. The multimodal grain structure, characterized by three distinct grain size distributions and a strong basal texture, arises from partial dynamic recrystallization during hot rolling. The hierarchical precipitates include microscale rod-like and particle-like β phase at grain boundaries, twins, and deformation bands, as well as nanoscale β phase precipitates (~63nm) dispersed within the grain interiors. The fully β precipitates also demonstrate a modified precipitation pathway, differing from the β' and γ'' nanoprecipitates observed in conventional Mg-Gd-Ag alloys. This unique microstructure results in an ultimate tensile strength of 447MPa, primarily attributable to the strong basal texture, hierarchical precipitates, hetero-deformation-induced (HDI) strengthening, and high dislocation density.

Where Have All the Sulfur Atoms Gone? Polycyclic Aromatic Hydrocarbon as a Possible Sink for the Missing Sulfur in the Interstellar Medium. I. The C–S Band Strengths

Despite its biogenic and astrochemical importance, sulfur (S), the 10th most abundant element in the interstellar medium (ISM) with a total abundance of S/H ≈ 2.2 × 10−5, largely remains undetected in molecular clouds. Even in the diffuse ISM where S was previously often believed to be fully in the gas phase, in recent years, observational evidence has suggested that S may also be appreciably depleted from the gas. What might be the dominant S reservoir in the ISM remains unknown. Solid sulfides like MgS, FeS, and SiS2 are excluded as major S reservoirs due to the nondetection of their expected infrared spectral bands in the ISM. In this work, we explore the potential role of sulfurated polycyclic aromatic hydrocarbon (PAH) molecules—PAHs with sulfur heterocycles (PASHs)—as a sink for the missing S. Utilizing density function theory, we compute the vibrational spectra of 18 representative PASH molecules. It is found that these molecules exhibit a prominent C–S stretching band at ∼10 μm and two relatively weak C–S deformation bands at 15 and 25 μm that are not mixed with the nominal PAH bands at 6.2, 7.7, 8.6, 11.3, and 12.7 μm. If several parts per million of S (relative to H) are locked up in PAHs, the 10 μm C–S band would be detectable by Spitzer and the James Webb Space Telescope (JWST). To quantitatively explore the amount of S/H depleted in PASHs, a detailed comparison of the infrared emission spectra of PASHs with the Spitzer and JWST observations is needed.

Influence Mechanisms of Cold Rolling Reduction Rate on Microstructure, Texture and Magnetic Properties of Non-Oriented Silicon Steel

The effects of cold rolling reduction on the microstructure, recrystallization behavior, and magnetic properties of 3.0%Si-0.8%Al-0.3%Mn steel were studied by X-ray diffraction (XRD) and electron backscatter diffraction (EBSD). With the reduction rates of 78%, 85% and 87% in the cold rolled sheet, the width of the deformation band becomes narrower, the number of intragranular shear bands decreases, and the proportion of grain boundaries increases. The intensity of the α and γ fibers texture in the cold rolled sheet is enhanced, and the annealed sheet is dominated by the γ fibers texture and the content increases from 26.0% to 34.5%. During the recrystallization process, the Goss and γ-grains nucleate first. The λ-grains nucleate mainly at the grain boundaries of the deformed α-grains, and the α-grains ultimately recrystallize. With the increase in the cold rolling reduction rate, the γ-grains develop into the main texture due to a large amount of nucleation at the deformation band and grain boundary. The λ-grains with a high mobility do not have a numerical advantage, and the increase in the texture content is very small. The content of the unfavorable γ fiber texture in the annealed sheet increases, the magnetic induction intensity B50 decreases, Pe and Pt decrease significantly, and the critical grain size with the lowest iron loss decreases from 136.2 to 109.4 μm.

Cross-rolling induced texture randomization and structural evolution for improved plastic isotropy in Al-Mg alloys with high Mg content

Plastic anisotropy is a key factor that affects the formability and performance of Al-Mg alloys. In this study, the effects of Mg content and strain path shifting from unidirectional rolling (UDR) to cross rolling processes (CR) on plastic anisotropy in Al-Mg alloys were investigated. Al-6 and 9Mg alloys were heat-treated and rolled in two different ways: the first was a UDR process, and the other was a CR process at room temperature. The rolled specimens were analyzed by electron backscattered diffraction method and tensile test. High Mg content suppresses the formation of texture that strengthens the plastic anisotropy in both UDR and CR processes. CR significantly reduces the rolling texture area fraction, leading to greater texture randomness compared to UDR. CR promotes the formation of low-angle deformation bands, which low-angle bands appear to have a weaker impact on deformation resistance and may contribute to the reduced anisotropy in CR-processed materials. CR results in a more uniform distribution of stored energy. R-value which represents plastic anisotropy decreases by shifting from UDR to CR, and by increment of Mg content. Overall, this study demonstrates that CR is a promising approach for improving the formability and performance of Al-Mg alloys by effectively controlling plastic anisotropy.

The Influence of Microstructure and Process Design on the Plastic Stability of 4 wt% Medium‐Manganese Steels

The influence of different microstructures on the plastic stability of an air‐hardened industrially produced medium‐manganese steel is presented. For this matter, heat treatment parameters before and during intercritical annealing (IA) are varied, to achieve different microstructures. The resulting duplex microstructure is consecutively tested by tensile tests, which are monitored by digital image correlation (DIC) to obtain information on the local plastic deformation. The tests are accompanied by microstructure investigations using optical, scanning electron, and transmission electron microscopy. Finally, X‐ray and electron backscatter diffraction experiments are performed before and after deformation, to describe the altering phase fractions. It is demonstrated that the effect of the deformation temperature prior to IA treatment has a significant influence on the duplex microstructure, as it changes the austenite morphology from lamellar to globular and increases the phase fraction. The change in austenite phase fraction and morphology results in a higher yield strength (≈100 MPa), as well as higher uniform and total elongations (+2% and +5%, respectively). The DIC and tensile tests reveal that these differences in the austenite phase lead to a complete change in the strain hardening behavior, from continuous flow to discontinuous serrated flow, with clearly visible deformation bands during plastic deformation.

Investigating microstructure dynamics and strain rate sensitivity in gradient nanostructured AISI 304 L stainless steel: TEM and nanoindentation insights

In recent years, gradient nanostructured (GNS) materials have gained significant attention due to their superior strength-ductility balance and enhanced functional properties compared to their coarse-grained counterparts. This research examines the microstructure evolution and nanomechanical responses of GNS AISI 304 L austenitic stainless steel using transmission electron microscopy (TEM) and nanoindentation techniques. Through surface mechanical attrition treatment (SMAT), a gradient nanostructured layer with ultrafine grains (∼15 nm) and nanoscale martensite (up to ∼40 %) within the austenite matrix has been successfully created on the steel’s surface. This treated surface exhibits a hardness of ∼6.7 GPa, nearly double the original value. The GNS layer demonstrates single-step (γ → α’) and two-step (γ → ε → α’) martensitic transformations, deformation twinning (γ -twin), a decrease in the density of deformation bands, compressive residual stress, lattice strain, and martensite content, along with an increase in grain size. Strain rate sensitivity (SRS) increases with austenitic grain size and inversely correlates with martensite proportion as depth increases in the GNS layer. A significant amount of ultrafine martensite is primarily responsible for the limited SRS in the topmost layer.

Comparison on Hysteresis Loops and Dislocation Configurations in Fatigued Face-Centered Cubic Single Crystals

The aggregation and evolution of dislocations form different configurations, which are the preferred locations for fatigue crack initiation. To analyze the spatial distribution of the same dislocation configuration and the resulting configuration morphologies on different observation planes, several typical hysteresis loops and dislocation configurations in fatigued face-centered cubic single crystals with various orientations were compared. The crystal orientations of these specimens were determined by the electron back-scattering diffraction technique in a Cambridge S360 Scanning Electron Microscope. It is well known that dislocation ladder and wall structures, as well as patch and vein structures, are distributed on their respective observation planes, (12¯1) and (111). These correspond to the point defect direction and line defect direction of dislocations, respectively. Therefore, the wall structures on the (12¯1) and (111) planes consist of point defects and line defects, which can be defined as point walls and line walls, respectively. Furthermore, the walls on the (12¯1) plane consist of Persistent Slip Band ladders connected with each other, corresponding to the formation of deformation bands. The evolution of dislocation patterns follows a process from patch to ladder and from vein to wall. The formation of labyrinths and dislocation cells originates from the activation of different secondary slip systems. In one word, it can help us better understand the physical nature of metal fatigue and failure by studying the distribution and evolution of different configurations.

Permeability partitioning through the brittle-to-ductile transition and its implications for supercritical geothermal reservoirs

Geothermal projects utilizing supercritical water (≥400 °C) could boost power output tenfold compared to conventional plants. However, these reservoirs commonly occur in crustal areas where rocks are semi-ductile or ductile, impeding large-scale fractures and cracking, and where hydraulic properties are largely unknown. Here, we explore the complex permeability of rocks under supercritical conditions using mechanical data from a gas-based triaxial apparatus, high-resolution synchrotron post-mortem 3D imagery, and finite element modeling. We report a first order control of strain partitioning on permeability. In the brittle regime, strain localizes on permeable faults without necessarily increasing sample apparent permeability. In the semi-ductile regime, distributed strain increases permeability both in deformation bands and the bulk, leading to a more than tenfold permeability increase. This study challenges the belief that the brittle-ductile transition (BDT) marks a cutoff for fluid circulation in the crust, demonstrating that permeability can develop in deforming semi-ductile rocks.

Enhanced soft magnetic properties with high frequency stability of pure iron powder cores via high-pressure compaction – An environment and cost saving solution as a prospective alternative to soft magnetic composites

The paper presents the analysis of the magnetic behaviour of soft magnetic powder compacts vs. the increasing compacting pressure. An unexpectedly positive result was obtained at a pressure of 1500 MPa, as the pure iron compact without coating of powder particles and without subsequent heat treatment showed very good magnetic properties compared to the class of soft magnetic composites (SMCs). In particular, the effective relative permeability of μeff ∼120, stable up to a frequency f ∼200 kHz, the maximum total relative permeability of μtotmax ∼700, and the specific electrical resistivity of ρR ∼10−5 Ω m. This phenomenon was explained on the basis of analyses of the samples microstructure, the magnetic and electrical properties, magnetization processes, inner demagnetizing fields, Barkhausen noise and thermal diffusivity. It was found that the grain size refinement inside iron particles occurs at certain elevated compaction pressure because the deformation bands gradually rise and break up with compaction pressure, leading to a higher resistivity of the compact thus to its SMC-like behaviour, despite the counteracting effect of increasing number of iron-iron bridges among neighbouring particles. The grain size refinement causes also the refinement of magnetic domain structure, which facilitates the magnetization reversal, although, the increased internal stresses and microstructural defects affect domain wall mobility negatively. The most favourable combination of the mentioned factors influences, finally resulting in the soft magnetic properties enhancement, appeared at 1500 MPa. Due to high-pressure compaction, the high density (above ∼95 % of iron density) of a compact was achieved, ensuring sufficient mechanical properties. The presented material can serve as a potential supplanter of SMCs in many applications as it provides evident advantages, such as its easy production with minimum chemical waste (because any additional chemical processes and substances needed for particle coatings in conventional SMCs are completely omitted), as well as easy recycling process, which makes it eco-friendly and cost-effective, nevertheless, maintaining the advantages of SMCs.

Multi‐mode gravity tectonics during northern North Sea rifting: the Snorre fault block case

AbstractContinental rifts are characterized by up to 30 km wide rotated fault blocks with stratigraphic dip away from the central rift axis. Although gravity‐induced mass movements are well known features of collapsed fault block crests, I here demonstrate the occurrence of polymodal gravity‐driven mass transport down the back slope of a first‐order rift fault block. I identify (1) early sliding related to syntectonic crestal collapse of second‐order rift faults, (2) large‐scale bed‐parallel sliding of the L‐M Jurassic sedimentary package, and (3) the accumulation of two 7 km long, 1–2 km wide and up to 750 m thick volumes of complexly slumped material in the hanging walls of two ramp‐forming faults. Early sliding is documented by 100 m of repeated Brent Group stratigraphy in a cored well in the study area (well 34/4‐15A). These smaller slides have intact internal stratigraphy but show elevated deformation band densities. The seismic data also show evidence for ca. 2 km of massive translational sliding of the ca. 400 m thick and ca. 300 km2 large Jurassic section above a lowermost Jurassic bedding‐parallel detachment. This translational slide did not deform much internally, except for ductile folding where it slid over underlying active rift faults. Chaotic seismic facies in fault hanging walls are interpreted as contorted Jurassic beds, formed by multiple slumping and sliding events that stacked mobilized sediments into a 750 m thick column. These complex slump volumes occur where fault displacement is highest along two relayed faults. A model is favoured where the large translational slide ruptured with an opening of space against the fault that was progressively filled with slumped material from the footwall. While the large‐scale translational sliding only caused moderate internal subseismic deformation, early sliding and, particularly, the complex slumping caused significant internal deformation. This study shows the importance of carefully searching for and distinguishing between different types of mass movement in rift systems.

Hot Workability and Microstructure Evolution of Homogenized 2050 Al-Cu-Li Alloy during Hot Deformation.

For this article, hot compression tests were carried out on homogenized 2050 Al-Cu-Li alloys under different deformation temperatures and strain rates, and an Arrhenius-type constitutive model with strain compensation was established to accurately describe the alloy flow behavior. Furthermore, thermal processing maps were created and the deformation mechanisms in different working regions were revealed by microstructural characterization. The results showed that most of the deformed grains orientated toward <101>//CD (CD: compression direction) during the hot compression process, and, together with some dynamic recovery (DRV), dynamic recrystallization (DRX) occurred. The appearance of large-scale DRX grains at low temperatures rather than in high-temperature conditions is related to the particle-stimulated nucleation mechanism, due to the dynamic precipitation that occurs during the deformation process. The hot-working diagrams with a true strain of 0.8 indicated that the high strain-rate regions C (300 °C-400 °C, 0.1-1 s-1) and D (440 °C-500 °C, 0.1-1 s-1) are unfavorable for the processing of 2050 Al-Li alloys, owing to the flow instability caused by local deformation banding, microcracks, and micro-voids. The optimum processing region was considered to be 430 °C-500 °C and 0.1 s-1-0.001 s-1, with a dissipation efficiency of more than 30%, dominated by DRV and DRX; the DRX mechanisms are DDRX and CDRX.