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Low-temperature, low-pressure Cu-to-Cu direct bonding technology is a promising solution for next-generation high-density interconnects. Previous studies have shown that many properties of nanomaterials are determined by their structural characteristics. Therefore, the effect of the nanostructure (i.e., twin crystal and twin boundary, TB, sizes) on the bonding mechanism and mechanical response of the direct bonding of (111)-oriented nanotwinned Cu (NT-Cu) is studied using molecular dynamics simulations, where TB size means the TB layer thickness in terms of the number of atoms. The simulation results show that NT-Cu with extremely small twin crystals (e.g., 0.625 nm) have poor diffusivity. The number of dislocations induced by plastic deformation increases with increasing twin crystal size during stretching processes, degrading mechanical strength. The strain hardening of bonded NT-Cu with extremely small twin crystals (e.g., 0.625 nm) is dominated by the strong barrier created by a high density of TBs, whereas that with twin crystal sizes of 2.5–10 nm is dominated by dislocation–TB and dislocation–grain boundary interactions. Bonded NT-Cu with 2–6 atoms per TB layer exhibits softening at initial plastic deformation due to the onset of partial collapse of TBs; however, the strength then significantly increases with a further increase in strain due to strain hardening. [ABSTRACT FROM AUTHOR]

Applying graphene (Gr) coatings to high-entropy alloys (HEA) is anticipated to enhance their tribological characteristics. The current understanding of the mechanism by which the Gr/HEA is enhanced at the atomic level is still limited. Molecular dynamics simulations revealed the mechanical behavior and strengthening mechanism of the Gr/AlCoCrFeNi HEA during nanoindentation and nanoscratch. The results demonstrate a substantial increase in the indentation hardness of the Gr/AlCoCrFeNi HEA by about 2.4 times. When Gr changed from a single layer to three layers, it further improved (3.2 times for a double layer and 3.9 times for three layers). At the same time, the friction coefficient is effectively reduced. Furthermore, the elevated in-plane stiffness of the Gr coating leads to an expansion of the effective loading area, resulting in increased Shockley dislocation and stair-rod dislocation density within the Gr/AlCoCrFeNi HEA, thereby amplifying the strain hardening effect and reducing subsurface damage. Qualitative experiments confirmed the excellent wear resistance of the Gr/HEA, and coating Gr increased the width of scratches, effectively confirming our simulation results. These findings provide valuable insights for the development and design of Gr/HEA composite coatings with enhanced mechanical properties. [ABSTRACT FROM AUTHOR]

We simulate an alloy of HfNbTaTi mixed in six different proportions and also of the equiatomic system under uniaxial tensile loading at 300 K. Molecular dynamics simulation trajectories are analyzed using radial distribution functions, OVITO, bond-orientational order parameters, and coordination numbers. Equiatomic and the two other alloys (Hf 0.31 Nb 0.23 Ta 0.23 Ti 0.23 and Hf 0.23 Nb 0.31 Ta 0.23 Ti 0.23 ) containing comparable fraction of elements deform similarly through the formation of an amorphous state. Two alloys rich in Nb (Hf 0.17 Nb 0.50 Ta 0.16 Ti 0.17 ) and Ta (Hf 0.17 Nb 0.16 Ta 0.50 Ti 0.17 ) deform similarly resulting in the formation of bcc atoms, which transform to fcc at higher loading. Finally, alloys rich in Hf (Hf 0.50 Nb 0.16 Ta 0.17 Ti 0.17 ) and Ti (Hf 0.17 Nb 0.16 Ta 0.17 Ti 0.50 ) deform resulting in high dislocation densities and hcp atoms. These two hcp-rich alloys also undergo strain hardening. In each mixture during loading, local orientational order of all the different elements changes similarly. Atoms prefer to pair with other atoms than to themselves during tensile loading. [ABSTRACT FROM AUTHOR]

Hydra has a tubular bilayered epithelial body column with a dome-shaped head on one end and a foot on the other. Hydra lacks a permanent mouth: its head epithelium is sealed. Upon neuronal activation, a mouth opens at the apex of the head which can exceed the body column diameter in seconds, allowing Hydra to ingest prey larger than itself. While the kinematics of mouth opening are well characterized, the underlying mechanism is unknown. We show that Hydra mouth opening is generated by independent local contractions that require tissue-level coordination. We model the head epithelium as an active viscoelastic nonlinear spring network. The model reproduces the size, timescale and symmetry of mouth opening. It shows that radial contractions, travelling inwards from the outer boundary of the head, pull the mouth open. Nonlinear elasticity makes mouth opening larger and faster, contrary to expectations. The model correctly predicts changes in mouth shape in response to external forces. By generating innervated : nerve-free chimera in experiments and simulations, we show that nearest-neighbour mechanical signalling suffices to coordinate mouth opening. Hydra mouth opening shows that in the absence of long-range chemical or neuronal signals, short-range mechanical coupling is sufficient to produce long-range order in tissue deformations.

In this paper, a new approach for rotational hardening in elastic-plasticity is formulated. After discussing the standard yield criteria employed for geomaterials and the rotational hardening models proposed in the past, the authors introduce the concept of pure rotational hardening, that is a rigid rotation of the yield surface not implying any distortion of it. In the second part of the paper, a new approach for rotational hardening, based on Householder transformations, is proposed. The method, that allows to reflect vectors with respect to a given hyper-plane, is briefly described since not usually employed in geomechanics. Moreover, the authors clarify that any yield surface or plastic potential rotation, not being a rolling, is a transformation keeping unaltered first and second invariants, but not the third. As a consequence, when rotational hardening is introduced, the use of the third mixed invariant, for defining in the deviatoric plane the yield surface shape, is not appropriate. Finally, the application of the proposed approach in the formulation of anisotropic elastic–plastic strain hardening constitutive models is briefly discussed for the classes of uncoupled and hybrid yield criteria that include a dependence of the yield surface on Lode angle. [ABSTRACT FROM AUTHOR]

The milling process is the standard method for producing flat tensile test specimens from sheet metal. However, alternative methods employed in the industry for cutting sheet metal include abrasive water jet cutting, laser cutting, punching, and, to a lesser extent, electrical discharge machining. Among these, abrasive water jet cutting stands out for its superior material integrity, versatility, precision, and efficiency, making it a preferred choice. Previous studies consistently show that specimens cut by abrasive water jetting exhibit lower ultimate tensile strength and higher percent elongation than those obtained by milling in standardized tensile tests. This study investigates this behavior across different types of steel and alloys. Both steel types were subjected to milling and water jetting processes, followed by an analysis of their experimental and simulated mechanical behavior to identify discrepancies between the two methods. The findings suggest that milling, influenced by factors such as feed per tooth and cutter diameter, introduces geometric stress concentrators. This relative increase in ultimate tensile strength and decrease in percent elongation are observed consistently in milled tensile specimens compared to those cut by water jet, regardless of material type or thickness. Additionally, the effects of perimeter hardening resulting from superficial plastic deformation caused by the cutting edge, likely due to its small thickness, do not influence the observed trends significantly. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This study investigated the fatigue fracture mechanisms and life prediction of clinched joints made from titanium alloy TA1. The fatigue tests revealed that TA1 titanium alloy clinched joints exhibited failure characterized by fracture of the lower plate at three distinct fatigue load levels. Additionally, finite element analysis indicated that cold work hardening enhanced the fatigue performance of these joints. Observations of fracture surfaces using scanning electron microscopy identified the crack source and its propagation path, which correlated with the location of maximum principal stress from the finite element simulations. Fretting wear was also observed in this critical region. Furthermore, fatigue life predictions for TA1 titanium alloy clinched joints were made using Paris' law and the local strain approach. Both methods closely matched experimental results across different fatigue life intervals. Overall, the local strain approach exhibited superior predictive capability compared to Paris' law, taking into account various influencing factors. [ABSTRACT FROM AUTHOR]

The softening of aluminum alloy is an important factor affecting its service life. In the present work, the softening characteristics and mechanism in the friction pull plug welding (FPPW) joint of AA2219-T87 plate with a nominal thickness of 18 mm were studied, and an effective measure to mitigate the softening issue was proposed. The softening zone in the thick-plate FPPW joint is located in thermo-mechanically affect zone near the bonding interface and is 6–12 mm away from the top surface of the plate. The disappearance of the strengthening transition phase θ′ is the main cause for the softening; the degree of dynamic recrystallization, which influences the grain size and the work hardening, also affects the softening; but solid solution of Cu atoms in α-Al has little effect on the hardness change in the softening zone. After optimizing the geometric structure of joint and FPPW process parameters, the softening zone was still the weakest point of the joint. After solution and aging treatment on the above-mentioned optimized joint, the minimum hardness in the softening zone increased from 76 HV1 to 95 HV1, the tensile strength increased from 318 to 355 MPa, and the fracture position shifted from the softening zone to the plug. [ABSTRACT FROM AUTHOR]

Numerous microcracks with different angles of inclination are found in brittle rocks. The crack angles lead to anisotropic properties of the compression failure of the rock, which greatly affects the evaluation of the stability of the surrounding rock in deep underground engineering. However, there are a few studies on the macroscopic mechanical relationship applicable to true triaxial stress between the three-dimensional inclination angle of a microcrack and the anisotropic compression failure in brittle rock. This paper aims to propose a microscopic anisotropic failure criterion applicable to various stress states including true triaxial compression to solve the problem of compression yield, strength, and damage of brittle rock. Introduce the three-dimensional angle of the initial crack into the expression for the stress intensity factor KI at the tip of the compression wing crack. When the newly obtained KI reaches the fracture toughness KIC, the rock yields. Then considering the exchange of the principal stress order and the property that the wing crack always cracks along the direction of the maximum principal compressive stress, the complete anisotropic yield surface form is obtained. The stress–crack extension length curve is plotted by f(σ1, σ2, σ3, l) = 0. The stress corresponding to l = 0 is regarded as the yield stress, the peak of the stress as the strength, and the stress at l = llim as the residual stress at damage. The work hardening and softening after yield are realized, so that the yield criterion can be extended to the strength criterion and the damage criterion, and the successive yield surfaces under arbitrary crack lengths can be derived. The reasonableness of the failure criterion is verified by comparison with mechanical experiments on different types of rocks under different stress conditions. The three-dimensional yield surface is projected onto the π-plane to analyze the influence law of parameters on typical stress points. And the three-dimensional yield surface is projected onto the tensile and compressive meridian planes to analyze the influence law of hydrostatic pressure on the yield stress of rock. [ABSTRACT FROM AUTHOR]

Surface deformation strengthening treatment could effectively enhance the fatigue properties of aerospace titanium alloy components, which is attributed to the occurrence of residual compressive stress and microstructure dual gradients. However, the evolution of the dual gradients during fatigue deformation has barely been studied, and the deformation mechanism is still puzzling. In this work, TC17 alloys were strengthened by ultrasonic shot peening (USP) treatment. The fatigue life of USP-20W is 73% higher than that of the original alloy. During fatigue deformation, the dislocation density in the surface and subsurface layers is further increased to enhance work hardening, while the < 001 > β//LD texture and < 111 > β//LD texture rotate towards the < 112 > β//LD texture for balancing strength and plasticity. Notably, the fatigue crack initiation site of USP-20W was located approximately 80 μm below the surface. It is attributed to the dislocation accumulation and local stress concentration caused by the orientation mutation of β-Ti, which favors the formation of a localized weak zone for fatigue damage. This finding holds substantial significance for optimizing material performance in aerospace components. [ABSTRACT FROM AUTHOR]

Data are presented from tensile tests of commercial Nb-based alloy C103 (Nb-10Hf-1Ti, by wt pct) at temperatures of 1550–1750 °C and true-strain rates of 3 × 10 - 5 to 3 × 10 - 3 s - 1 . Changes in strain rate generated pronounced short-term transients in flow stress. These transients are of the inverse type characteristic of solute drag creep (SDC). C103 produced large tensile elongations of 150–200 pct and strain hardened during plastic deformation. Test data provide an average strain-rate sensitivity of 0.29 and an activation energy for creep of 340 kJ/mol. Short-term transient data indicate a stress dependence for dislocation glide velocity of v ¯ ∝ σ 2.7 and for mobile dislocation density of ρ ∝ σ 0.7 . The deformed microstructure contains indistinct subgrains and steep strain gradients. All data indicate deformation by SDC controlled by the diffusion of Hf solute atoms for the range of conditions examined. Data from plastic flow transients suggest that creep rates for C103 available in the literature are likely from the primary creep region. When that is considered, data from the literature and the present study are in good agreement. [ABSTRACT FROM AUTHOR]

In this research, a 3D multiscale model was applied for the analysis of long-term deformation of mudstone under high stress. Firstly, Voronoi tessellation generating and cohesive elements inserting programs were developed by Python-driven ABAQUS to establish a multiscale numerical analysis platform. In addition, creep damage effects for high stress were investigated through tests. Extended Drucker–Pranger model with strain hardening creep was developed for the calculation of mudstone viscoelastic plasticity. Finally, the creep damage model was integrated with multiscale analysis platform to evaluate the creep process of samples. The results verified that the developed model was effective in multiscale numerical analysis. [ABSTRACT FROM AUTHOR]

Given that electronic components often undergo intricate thermal and mechanical loads during operation, comprehensively understanding lead-free solder, particularly solder based on β -Sn, in various complex load conditions, plays a crucial role in ensuring the structural integrity and functional reliability of integrated circuits. Therefore, investigating the mechanical properties and fracture behavior of β -Sn as a solder material holds paramount importance. In this study, we performed molecular dynamics simulations using the modified embedded atom method to investigate the mechanical properties and crack propagation of single-crystal β -Sn under different strain rates. The research findings demonstrate that as the strain rate increases, the single-crystal β -Sn exhibits elevated yield strength, fracture strength, and strain, while the elastic modulus decreases. Under higher strain rates, the relationship between dislocation density and strain rate in single-crystal β -Sn is quantitatively elucidated. The substantial increase in internal dislocation density imparts conspicuous strain hardening to the material, rendering plastic deformation more challenging. This observation sheds light on the microscale mechanism of strain hardening at the atomic level. Our results shall facilitate a deeper investigation into the mechanical behavior of single-crystal β -Sn while also paving the path for optimizing the design and application of lead-free solder materials in the electronics industry. [ABSTRACT FROM AUTHOR]

This study investigates the effects of heating processes on the microstructure and deformation behavior of medium Mn steel during warm deformation. The samples treated by austenitization maintain an austenitic microstructure during deformation, which transforms into martensite upon cooling to room temperature. In contrast, the room‐temperature microstructure of samples deformed by direct heating to the deformation temperature is dependent on the deformation temperature: deformation above Ac3 results in a martensitic microstructure; deformation within the intercritical range (Ac1–Ac3) produces a mixture of ferrite, martensite, and austenite; and deformation below Ac1 yields a microstructure of ferrite and carbides at room temperature. When the microstructure only contains austenite during deformation, medium Mn steel exhibits excellent work‐hardening capability, characterized by a gradual increase in work hardening with strain until a dynamic balance between hardening and softening. Conversely, when ferrite is present in the microstructure during deformation, the flow behavior is dominated by ferrite, resulting in poor work‐hardening capability, with peak stress reached at low strain, followed by dynamic softening. Microstructure and stress–strain curve analyses reveal that, below 640 °C, ferrite exhibits higher strength than austenite. At 640 °C, the strengths of ferrite and austenite are approximately equal; above this temperature, austenite surpasses ferrite in strength. [ABSTRACT FROM AUTHOR]

Two indices, indicating the regional average stiffness and the pace of strain hardening respectively, are derived from the nonlinear stress–strain behavior obtained from biomechanical analysis of aneurysm. A comprehensive method based on electrocardiographic‐gated multidimensional dynamic computed tomography angiography (MD CTA) is developed for extracting these mechanical characteristics in vivo. The proposed indices are evaluated by 26 cases including 9 healthy, one aortosclerosis, and 16 abdominal aortic aneurysm cases. The difference of SSI and dSSI value between aneurysmal and healthy groups is up to orders in magnitude. Significant correlation of these indices with the clinical indicator of aneurysm diameter is found. Logistic models based on these indices are capable to sharply discriminate the healthy and the aneurysmal arteries with AUC>0.98. This work introduces new tools and new indices for aortic mechanical assessment which may shed light on understanding the mechanical condition, pathological state and eventually benefit clinical decision‐making. [ABSTRACT FROM AUTHOR]

ABSTRACT This study investigates the effect of ultrasonic shot peening (USP) on Ti‐6Al‐4V samples using cast steel and zirconia ceramic shots at the same intensity. The surface integrity of the samples before and after treatment was characterized, and tensile–tensile fatigue tests were conducted under various stress amplitudes to compare the improvements in fatigue performance. The mechanisms underlying the enhancement of fatigue properties were analyzed by examining microstructural changes and fracture morphologies. The results show that, compared to steel shot, zirconia ceramic shot leads to lower surface roughness, finer surface grains, and more significant work hardening and plastic deformation. These factors contribute to a more pronounced improvement in the fatigue performance under tension–tension loading of Ti‐6Al‐4V under USP treatment. The superior performance of ceramic shot can be attributed to low density combined with high hardness of the ceramic shot. [ABSTRACT FROM AUTHOR]

The mechanical properties of lignin, an aromatic heteropolymer constituting 20–30% plant biomass, are important to the fabrication and processing of lignin-based sustainable polymeric materials. In this study, atomistic simulations are performed to provide microscopic insights into the mechanics of lignin. Representative samples of miscanthus, spruce, and birch lignin are studied. At room temperature below the glass transition temperature, the stress–strain curves for uniaxial compression and tensile loading are calculated and analyzed. The results show that lignin possesses rigidity with a Young's modulus in the order of GPa and exhibits strain hardening under strong compression. Meanwhile, lignin is brittle and fails through the microscopic mechanism of cavitation and chain pullout under local tensile loading. In addition to the three common lignin samples, minimalist model systems of monodisperse linear chains consisting of only guaiacyl units and β -O-4 linkages are simulated. Systematic variation of the model lignin chain length allows a focused examination of the molecular weight effects. The results show that the molecular weight does not affect the Young's modulus much, but higher molecular weight results in stronger strain hardening under compression. In the range of molecular weight studied, the lignin chains are not long enough to arrest the catastrophic chain pullout, explaining the brittleness of real lignin samples. This work demonstrates that the recently modified CHARMM force fields and the accompanying structural information of real lignin samples properly capture the mechanics of lignin, offering an in silico microscope to explore the atomistic details necessary for the valorizaiton of lignin. [ABSTRACT FROM AUTHOR]

We studied the rheological properties under both shear and elongational flow and crystallization behaviors after shear history for binary blends of poly(lactic acid) (PLA) and ethylene–vinyl acetate copolymer (EVA) with a slightly lower shear viscosity. EVA was immiscible with PLA and dispersed in droplets in the blend. The addition of EVA significantly reduced the shear viscosity, which is attributed to the interfacial slippage between PLA and EVA. In contrast, under elongational flow, the addition of EVA provided strain hardening in the transient elongational viscosity. Consequently, the degree of neck-in behavior in T-die extrusion, i.e., a decrease in the film width, was reduced with the high orientation of the PLA chains. Furthermore, it was found that the addition of EVA accelerated the shear-induced crystallization of PLA, although EVA showed no nucleating ability without a flow field. Because the EVA addition can improve the mechanical toughness, this modification technique is attractive for various industrial applications of PLA. [ABSTRACT FROM AUTHOR]

The effects of aging treatment and the volume fraction of precipitation particles on the nano-hardness and nano-indentation morphology of Ni-based single crystal superalloys are systematically investigated. Using nano-indentation tests and atomic force microscopy (AFM), this study examined the mechanical properties and related physical mechanisms of Ni-based superalloys that have two volume fractions of precipitation particles and four aging treatment times. Results analyzed using the Oliver–Pharr method indicate that prolonging the aging time or increasing the volume fraction of particles enhances the nano-hardness and creep resistance of Ni-based single crystal superalloys and reduces the indentation-affected area. Additionally, the nano-hardness and elastic modulus decrease gradually with increasing applied force, revealing an obvious indentation size effect. These variations are closely linked to the size and density of particles and work hardening rate, as well as to the topologically close-packed (TCP) phases, which influence dislocation movement and accumulation within the material and lead to various nano-indentation behavior in Ni-based single crystal superalloys. The related study provides theoretical guidance and experimental data to support the design and application of superalloys. [ABSTRACT FROM AUTHOR]

Heterostructured (HS) materials, characterized by heterogeneous zones with differences in mechanical or physical properties, represent a revolutionary advancement in material science. During deformation, hetero‐deformation‐induced (HDI) stress forms due to the synergistic interactions between soft and hard zones, leading to remarkable HDI strengthening and strain hardening. This mechanism significantly enhances their performance, surpassing that of traditional homogeneous materials. This review delves into the classification, preparation techniques, fundamental deformation mechanisms, and research methods of HS materials. It outlines the preparation methods of various HS materials, emphasizing their unique characteristics and applications. The review elaborates on the fundamental deformation mechanisms of HS materials, focusing on non‐uniform plastic deformation behavior and HDI strain hardening. Furthermore, it explores the application of heterogeneous design concepts in materials, analyzing their microstructure tuning mechanisms and mechanical properties. This review aims to serve as a critical reference for the future design and development of new HS metallic structural materials, paving the way for innovations that can transform multiple industries. By highlighting the long‐term impact, this review not only enhances the understanding of HS materials but also provides a roadmap for future research and industrial applications, positioning HS materials as key players in the advancement of material technology. [ABSTRACT FROM AUTHOR]

Cu–Al alloy with a gradient nanostructured surface layer is prepared by ultrasonic shot peening (USP). The effect of different shot peening times on the microstructure and properties of the modified layer is systematically investigated. The results show that the surface phase structure is not changed by USP technology, but a gradient nanocrystalline layer is formed on the surface, and the surface grains are obviously refined. The nanocrystalline mechanism is characterized by dislocation movement and mechanical twinning. USP can greatly improve the mechanical properties, tribological properties, and corrosion properties of the alloy. When the shot peening time is 15 min, the modification effect is the best. The hardness is as high as 254.1 HV0.2, which is 2.4 times that of the matrix, and the average coefficient of friction is only 0.231. The volume wear amount and volume wear rate are 4.434 × 107 μm3 and 0.1848 μm2 N−1, respectively. The strengthening mechanism of nanosized samples is grain refinement and work hardening, and the wear mechanism is abrasive wear and slight oxidation wear. The improvement of the corrosion performance of nanosized samples is mainly due to the formation of the dense passivation film on the surface. [ABSTRACT FROM AUTHOR]

This paper conducts triaxial undrained tests on flocculated and dispersed kaolin samples at strain rate range 0.005–1%/min to investigate the effects of structure and strain rate on shear strength. The test results show that the flocculated samples exhibit strain hardening behaviour, while the dispersed samples show strain softening behaviour. The strain rate sensitivity parameter reflects the degree to which shear strength increases with increasing strain rate. The structure affects the strain rate sensitivity parameter, with values of 4.79% and 2.31% for flocculated and dispersed samples, respectively. When the strain rate is 1%/min, due to the low permeability of the dispersed sample, the high strain rate causes a rapid increase in local pore pressure, while the postponed dissipation of excess pore pressure destroys the sample. When studying the influence of clay structure, it is important to use the same strain rate; otherwise, the differences in shear strength may be underestimated. [ABSTRACT FROM AUTHOR]

The influence of different aluminum concentrations (0 and 0.25 wt%) on the mechanical properties and the microstructure of recently developed air‐hardening ductile forging steels with 4 wt% manganese is presented together with the effects of additional heat treatments after air cooling. Based on the achieved mechanical properties, the necessity of aluminum alloying is evaluated due to the processing challenges associated with the Fe–Mn–Al–Si system. For this matter, tensile properties, hardness, and Charpy impact toughness areevaluated with respect to microstructural features characterized by light optical microscopy and scanning electron microscopy equipped with electron backscatter diffraction (EBSD). It is demonstrated that the intermediate addition is not sufficient to reach the target values for the impact toughness, which demonstrates the importance of the addition to this steel grade. Additionally, insights on the tempering embrittlement are gained, as it can be shown that 0.25 wt% Al is sufficient to shift the tempering embrittlement from 300 to 350 °C. Finally, potential intercritical annealing temperatures can be specified: while high balances of strength and ductility can be reported at 650 and 675 °C, an exceeding of this temperature leads to insufficient austenite stabilization and consecutively martensite formation during cooling , as demonstrated by EBSD and X‐ray diffraction. [ABSTRACT FROM AUTHOR]

This study delves into the interplay between crystallographic texture, microstructure, and mechanical behavior in pulse laser powder bed-fused (LPBF) 316L stainless steel subjected to uniaxial tensile loading. The as-built microstructure exhibits a hierarchical arrangement spanning macro, micro, and nanoscales, showcasing chemical uniformity and minimal elemental segregation owing to the rapid cooling rate intrinsic to LPBF, distinct melt pool formations, and the emergence of nanosized silicon-rich oxides. The additive manufacturing process induces a network of dislocations, imparting twinning-induced plasticity (TWIP) behavior to 316L stainless steel. This is characterized by a distinctive five-stage strain hardening process. Maintained pre-existing dislocation networks enhance nanotwin creation, fostering interactions between different types of dislocations. Deformation-induced nanotwins contribute to a sustained elevated strain hardening rate through two stages. This effect is reinforced by the development of pronounced < 111 > and α-fiber textures, aligned with the tensile direction. Additionally, the alloy's high yield strength is attributed to the dense dislocation cell population. These dislocation cells, coupled with distributed nanooxide inclusions, facilitate the formation of nanometer-scale ductile dimples, effectively impeding crack propagation and mitigating defects compared to conventional manufacturing methods. In summary, plastic deformation hinges on dislocation glide and deformation-induced twinning, culminating in a final microstructure featuring diverse twin types and highly misoriented dislocation boundaries. This comprehensive understanding sheds light on the intricate relationship between microstructural attributes and mechanical performance in LPBF 316L stainless steel. [ABSTRACT FROM AUTHOR]

Refractory high‐entropy alloys (RHEAs) inspire the development of novel high‐temperature structural materials due to their outstanding resistance to softening and phase stability at elevated temperatures. However, they struggle to simultaneously achieve high‐temperature strength and room‐temperature ductility, while exhibiting insufficient room‐temperature strain hardening capability. Heterogeneous structure strengthening possesses a unique plastic self‐coordinated ability, which can effectively maintain strain hardening rate to achieve an excellent combination of strength and ductility. Benefiting from slow atomic diffusion, severe lattice distortion, and broad compositional design space, RHEAs with heterogeneous structures can be prepared from both chemical composition and interface structure perspectives. Chemical composition heterogeneity primarily focuses on fluctuations of alloying elements at the nanoscale, along with the formation of heterogeneous precipitates and unique lamellar eutectic structures. While, interface structure heterogeneity manifests in the activation of phase transformation and twin boundaries within grains, along with the formation of grains of vastly different sizes. The trend in RHEAs development is toward structural‐functional integration. Heterogeneous structures can also optimize functional properties, such as irradiation resistance, biomedical properties, and high‐temperature softening resistance of RHEAs. Finally, a brief outlook is provided on the future development direction of heterogeneous structure RHEAs. [ABSTRACT FROM AUTHOR]

To examine the microstructural evolution that occurs during transient creep, we deformed samples of polycrystalline olivine to different strains that spanned the initial transient deformation. Two sets of samples with different initial grain sizes of 5 μm and 20 μm were deformed in torsion at T = 1,523 K, P = 300 MPa, and a constant shear strain rate of 1.5 × 10−4 s−1, during which both sets of samples experienced strain hardening. We characterized the microstructures at the end of each experiment using high‐angular resolution electron backscatter diffraction (HR‐EBSD) and dislocation decoration. In the coarse‐grained samples, dislocation density increased from 1.5 × 1011 m−2 to 3.6 × 1012 m−2 with strain. Although the same final dislocation density was reached in the fine‐grained samples, it did not vary significantly at small strains, potentially due to concurrent grain growth during deformation. In both sets of samples, HR‐EBSD analysis revealed that intragranular stress heterogeneity increased in magnitude with strain and that elevated stresses are associated with regions of high geometrically necessary dislocation density. Further analysis of the stresses and their probability distributions indicate that the stresses are imparted by dislocations and cause long‐range elastic interactions among them. These characteristics indicate that dislocation interactions were the primary cause of strain hardening during transient creep in our samples. A comparison of the results to the predictions of three recent models reveals that the models do not correctly predict the evolution in stress and dislocation density with strain in our experiments due to a lack of previous such data in their calibrations. Plain Language Summary: Forces from earthquakes and melting glaciers cause short‐term changes to the viscosity of rocks as they flow in Earth's mantle. Recent experiments have suggested that the extent of these changes is controlled by interactions among microscopic defects, called dislocations, within the lattices of crystals that make up the rocks. To be able to predict the effects of these changes on a global scale, we need to understand how the number of, and interactions among, these defects react to sudden changes in the forces driving deformation. To this end, we deformed rocks at high temperature and pressure and characterized the evolution of these defects during a change in stress. We found that the number of dislocations increased as the stress increased, as did the strength of interactions among dislocations. Our results give more support to the idea that interactions among dislocations control the evolution of the viscosity of the rocks. These results can be used to improve models that describe short‐term deformation of Earth's mantle. Key Points: Dislocation density increases with strain during transient creep and is correlated with increases in intragranular stress heterogeneityThe characteristics of intragranular stress heterogeneity indicate that long‐range interactions among dislocations control the stress evolution during transient creepRecent models were unable to reproduce the evolution of stress and dislocation density during transient creep, demonstrating a need to revisit these models [ABSTRACT FROM AUTHOR]

The combination of cold deformation and solution aging is an important technological route for the bar processing of superalloy fasteners. The microstructure evolution and mechanical properties are intimately related to the process parameters. In this study, we systematically elucidate the mechanical properties and microstructure evolution of Fe-15Cr-25Ni alloys in different treatment processes and conduct in-depth analysis of the synergistic strengthening mechanism of fine-crystal strengthening, second-phase strengthening, and work hardening on Fe-15Cr-25Ni alloys. The results show that the tensile strength and yield strength at room temperature increase with the increase in grain refinement and dislocation density but decrease with the increase in elongation. After solid-solution treatment, most of the precipitates dissolve into the matrix, and the dislocation density is greatly reduced, resulting in a decrease in strength and an increase in plasticity. After aging, a large amount of γ′ phase was precipitated. Due to the two strengthening effects of dislocation strengthening and second-phase strengthening, the strength of the aging state is more improved than that of the cold-drawing state. The purpose of this study is to provide valuable insights for the industrial production of Fe-15Cr-25Ni superalloys. [ABSTRACT FROM AUTHOR]

Ethylene/1-octene copolymers exhibit enhanced flexibility and impact resistance compared to polyethylene, which makes them well suited for applications in advanced plastics and elastomers. United-atom molecular dynamics (MD) simulations were conducted to explore the mechanical behavior and deformation mechanisms of ethylene/1-octene copolymers under uniaxial tensile loading. This study systematically examined the influence of temperature, polymer chain length, chain quantity, and strain rate, with a specific focus on how hexyl branch content impacts the mechanical properties of amorphous ethylene/1-octene copolymers. The simulation results indicate that as the branch content increases, the yield strength and elastic modulus decrease, suggesting a trade-off between flexibility and mechanical strength. Energy decomposition analysis reveals that copolymers with more branched chains undergo greater changes in van der Waals energy. Additionally, as the branch content increases, the reduction in dihedral angle energy in the strain hardening region becomes more gradual, and the rate and the extent of the transition of dihedral angles from gauche to trans conformation decrease under deformation. Ethylene/1-octene copolymers exhibit higher chain entanglement parameters compared to linear polyethylene, with these parameters increasing as the branch content rises. Moreover, increasing the branch content results in a less pronounced increase in chain orientation along the loading direction. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pulsed-wave laser powder bed fusion achieves high yield strength in CrCoNi alloy. • Extra thermal cycles trigger uniform high-density dislocations in cell interiors. • Early activation of deformation twinning contributes to a steady work hardening. • Uniform distribution of strengthening sources reduces the sacrifice of ductility. One of the most popular medium- and high-entropy alloys is CrCoNi alloy, renowned for its outstanding mechanical properties, particularly at cryogenic temperatures. However, further enhancing the yield strength of CrCoNi at room temperature while maintaining its high ductility remains challenging. In this study, we explore the potential of using a pulsed-wave laser in the powder bed fusion, a dominant metal additive manufacturing (AM) technique, to achieve exceptional room-temperature strength–ductility synergy in CrCoNi alloy. The pulsed-wave laser induces extra thermal cycles, generating additional pre-existing dislocations that are uniformly distributed within the interiors of solidification cells, a phenomenon distinct from conventional AM. These pre-existing dislocations not only enhance the room-temperature yield strength exceeding 800 MPa but also trigger the onset of deformation twinning prior to 2% strain. This early activation of deformation twinning contributes to steady work hardening throughout the entire plastic deformation, resulting in a large uniform elongation of nearly 40%. Our work offers valuable insights for designing novel AM processes with pulsed-wave lasers to advance the fabrication of high-value and high-performance alloys. [ABSTRACT FROM AUTHOR]

In this study, we prepared unentangled and slightly entangled poly(L-lactic acid) telechelic ionomer samples (Mn=5 and 16 kg/mol) based on sodium sulfonate groups. The telechelic samples exhibit extremely slow crystallization kinetics below the melting temperature Tm and above the glass transition temperature Tg, which enables us to examine the linear viscoelasticity of the ionomer melt samples therein. The application of either the shear flow (at 85 °C) or elongational flow (between 70 and 90 °C) strongly accelerates the crystallization, leading to strong strain hardening and formation of highly oriented α crystals. Depending on the relative average rates of the strain-induced dissociation and strain-induced crystallization, the stress evolution can be classified into two cases, and the critical work for strain-induced crystallization is higher in case where the strain-induced dissociation occurs earlier than the strain-induced crystallization. [ABSTRACT FROM AUTHOR]