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Hydrogen-induced damage is an inevitable challenge in pipeline safety applications, especially, the fusion welded joints owing to microstructure heterogeneity caused by welding process. In this work, X100 pipeline steel was subjected to friction stir welding (FSW) at rotation rates of 300–600 rpm under water cooling, and the relationship among the microstructure, hydrogen diffusivity, and hydrogen embrittlement (HE) behavior of the nugget zone (NZ) were studied. The NZ at 600 rpm had the highest effective hydrogen diffusion coefficient (D eff) of 2.1 × 10−10 m2/s because of the highest dislocation density and lowest ratio of effective grain boundary. The D eff decreased with decreasing rotation rate due to the decrease of dislocation density and the increase of ratio of effective grain boundary, and the lowest D eff of 1.32 × 10−10 m2/s was obtained at 300 rpm. After hydrogen charging, the tensile strength of all specimens decreased slightly, while the elongation decreased significantly. As the rotation rate decreased, the elongation loss was obviously inhibited, and ultimately a lowest elongation loss of 31.8% was obtained at 300 rpm. The abovementioned excellent mechanical properties were attributed to the fine ferrite/martensite structure, low D eff , and strong {111}//ND texture dramatically inhibiting hydrogen-induced cracking initiation and propagation. • FSW of X100 steel was performed in water cooling, producing defect-free weld. • The diffusion behavior of hydrogen in the NZ was studies. • The effect of hydrogen on deformation and fracture behavior was analyzed. • The NZ with fine ferrite/martensite present high HE resistance. [ABSTRACT FROM AUTHOR]

Transport and loss of beam injected energetic particles (EPs) due to three-dimensional perturbations, associated with the external kink (XK) instability and fishbone-like mode (FLM), are numerically investigated utilizing the guiding center following code ORBIT for static toroidal plasmas in HL-2A. The perturbation structure for the XK is computed by the MARS-F code and then mapped to the Boozer coordinates as defined in ORBIT. The simulation shows that the EP profile experiences a significant change in the middle of the plasma column, when the XK-induced radial magnetic field perturbation amplitude, normalized by the equilibrium field, exceeds a threshold value of about 10 − 2 . The EP transport is found to be dominated by a diffusion process instead of convection. Furthermore, by scanning the perturbation frequency as a free parameter while maintaining the XK mode structure (thus mimicking the FLM as observed in DIII-D and JT-60U tokamaks), redistribution and loss of EPs are found to be substantially enhanced due to strong resonances between the FLM and EPs, when the mode frequency exceeds a threshold value of ∼2 kHz for the case considered. For either XK or FLM, the response of passing EPs to the perturbation is dominant due to the assumed tangential neutral beam injection. Most lost EPs due to these instabilities are initially passing particles but are eventually lost through trapped orbits. [ABSTRACT FROM AUTHOR]

In this work, the Al content-dependent microstructure evolution and oxidation behavior of co-sputtered CrAl alloyed coatings on Zr-4 alloy were systematically investigated in 1000 ℃ steam. Experimental results demonstrated that the microstructure of generated oxide scale transformed from a Cr 2 O 3 oxide layer with embedding discrete α-Al 2 O 3 particles at low Al contents to a continuous outer (α, θ)-Al 2 O 3 and inner Cr 2 O 3 bi-oxide layer at high Al contents. However, there appeared a unique eutectoid-like Cr 2 O 3 /α-Al 2 O 3 multilayered oxide scale in Cr-18.3Al coating, which conferred the sample with optimal oxidation resistance. The underlying oxidation mechanisms were rationalized by revealing the Al content dominated selective oxidation behavior. • Appropriate Al addition can improve the steam oxidation resistance of Cr coating. • Al content dependent microstructure transformation of oxide scale is revealed. • Unique Cr 2 O 3 /α-Al 2 O 3 multilayered oxide scale in Cr-18.3Al coating contributes to high oxidation resistance. • Oxide-scale structure dominated failure mechanisms of CrAl coatings are discussed. [ABSTRACT FROM AUTHOR]

Due to its service background, the thermal behavior of Ta films is substantially concerning to researchers, especially the heat-induced β-Ta to α-Ta phase transformation. In this work, the nanocrystalline Ta films with varying β/α phase ratios (0.85–0) were deposited and vacuum annealed at 200–800 °C to study the phase transformation behavior and mechanical properties. Partial phase transformation of β-Ta to α-Ta occurred at low temperature (200 °C) and complete transformation when the annealing temperature was raised to 800 °C. Moreover, an orientation relationship of β-<110>//α-<111> and β-{330}//α-{110} was concluded, and a hypothesis theory about the low-temperature phase transformation was proposed. Annealing hardening took place at 200–600 °C and softening at 800 °C in all the samples. The hardening is mostly due to the ordering of intergranular amorphous phases with the temperature increased, simultaneously bringing the increase of modulus. The annealing softening is governed by both grain coarsening and phase transformation, where the latter is dominated in high β fraction samples. • High-temperature induced grain boundary structure ordering promotes the hardening of Ta films at 200 °C–600 °C. • β-Ta to α-Ta phase transformation was found at a wide temperature range, which partially governs the softening of Ta at 800 °C. • A preferred orientation relationship of β-<110>{330}//α-<111>{110} was concluded • The influence of phase transformation on mechanical properties was independently quantified using a simple comparative method. [ABSTRACT FROM AUTHOR]

In this work, medium-Mn steel was friction stir welded and then intercritically annealed. Hydrogen diffusion and hydrogen embrittlement (HE) behavior in the nugget zone (NZ) were investigated. The as-welded NZ exhibited the highest HE index (HEI) of 79.2%, and hydrogen‑induced cracks propagated along the grain boundary, probably depending on grain boundary decohesion caused by H segregation. However, this condition was improved by post-welding annealing since fine lath reversed austenite, acting as a strong hydrogen trap, was introduced into the ferritic matrix, inhibiting the segregation of H to grain boundaries. Ultimately, the lowest HEI of 10.7% was obtained in the as-annealed NZ. • The austenite reversion kinetics in the NZ during post-welding intercritical annealing was simulated by DICTRA. • The behavior of hydrogen diffusion and embrittlement in the NZ were studied using H permeation tests and SSRT. • The behavior of H-induced cracks of the NZ was analyzed. • The lowest HEI of 10.7% was obtained in the as-annealed-620 NZ, much lower than that of the as-welded NZ. [ABSTRACT FROM AUTHOR]

With the monotonically increasing of W from 0 to 20 at. % in Ta-W films with Cr buffers, an abnormal phase evolution of α-Ta→β-Ta→α-Ta was found, which is due to the breaking and rebuilding of α-Ta nucleation. A small amount of W addition could disturb the epitaxial growth of α-Ta on Cr layers by refining the nucleus size. Nevertheless, as a completely miscible system, Ta-W solid solutions are preferred to possess the α-Ta structure. With the increasing W content, the nucleation barrier of α-Ta is correspondingly lower, facilitating the rebuilding of α-Ta growth. The effect of phase evolution competes with that of solid solution strengthening in the controlling mechanism of Ta-W hardness. The hardness of the sample with low W contents is largely influenced by the proportion of β-Ta, while the solid solution strengthening effect is more pronounced in high W. [Display omitted] [ABSTRACT FROM AUTHOR]

The medium-Mn steels with high strength and ductility can be used as a potential material in the engineering fields. However, the weld in the medium-Mn steel joint has extremely low ductility due to the existence of full martensite. In this work, a superior tensile strength of 1453 MPa and elongation of 32.7% was obtained in the weld of friction stir welded (FSWed) medium-Mn steel. This should be related to high volume fraction of austenite (24.4%) far higher than that of basal metal (15.1%). The formation mechanism of exceptionally high fraction of austenite was studied based on the transformation kinetics. The volume fraction of austenite in the weld predicted by classical model was only 15.4% much lower than the experimentally measured value, indicating that this model is not suitable for FSW. We applied various assumptions about the diffusivity of Mn in austenite and ferrite during simulation. Consequently, when the Mn diffusivity of austenite and ferrite was multiplied by 4000 and 1500 times, respectively, the simulated austenite volume fraction was well consistent with the experimental results. This was attributed to that the high density of dislocations introduced by strong plastic deformation of FSW promoted the Mn diffusion and the austenitic reverse transformation. • The weld contained a high volume fraction of austenite (24.4%) far higher than that of the basal metal. • The formation mechanism of exceptionally high fraction of austenite was studied based on the transformation kinetics. • A superior tensile strength of 1453 MPa and elongation of 32.7% was obtained in the weld of FSW medium-Mn steel. • The contribution of various strengthening mechanisms to yield strength was evaluated. [ABSTRACT FROM AUTHOR]

The high Mn steel (Mn ≥ 20 wt.%) is widely applied because of excellent cryogenic properties. In the fusion-welded high-Mn steel joint, the Mn vapor and segregation degrade the joint quality. Friction stir welding (FSW) produces a high-Mn steel joint without defect, but the nugget zone (NZ) exhibits a poor plasticity. In this work, the preheating was subjected to FSW high-Mn steel to improve the plasticity of the NZ. Compared with the as-welded NZ, the as-preheated NZ contained slightly coarser austenite with lower density of dislocations (6.7 × 1014 m−2), and had a lower stacking fault energy (SFE) (47.18 mJ m−2) at room temperature. The lower SFE caused the deformation mechanism of dislocation slip and active twinning-induced plasticity (TWIP) in the as-preheated NZ owing to the lower back stress and critical twinning stress. Subsequently, a high strength and plasticity product of 62 GPa% was achieved in the as-preheated NZ, which was consistent with high strain hardening rate. At cryogenic temperature of −196 °C, the SFE of the as-preheated NZ decreased to 35.66 mJ m−2, but more active TWIP besides dislocation slip was found during tension. Therefore, the as-preheated NZ exhibited excellent strength and plasticity product of 91.9 GPa%. Furthermore, the yield strength of the as-preheated NZ was slightly reduced, which was attributed to the decreased of dislocation density and grain growth. • The preheating was introduced into the friction stir welded high Mn steel. • The SFE of austenite in the as-welded and as-preheated NZs at room and cryogenic temperature was calculated. • The deformation behavior of the as-welded and as-preheated NZs at room and cryogenic temperature was studied. • The contribution of various strengthening mechanisms to yield strength was evaluated. • The as-preheated-320 NZ presented excellent strength and plasticity product at room and cryogenic temperature. [ABSTRACT FROM AUTHOR]

Electroreduction of water into hydrogen holds promise to deal with growing environmental pollution and energy crisis, but it relies on efficient catalysts for both hydrogen/oxygen evolution reaction, that normally contain precious metal. Here, based on first principles calculations, we identify Co-anchored α-In 2 Se 3 as a bifunctional catalyst that can operate for both hydrogen/oxygen evolution reaction. The chemical activity can be largely enhanced or optimized by electrostatic potential due to the polarization, even better than traditional one containing precious metal. Both hydrogen/oxygen evolution reaction are dependent on polarization direction of α-In 2 Se 3 and could occur on different polarization domains separately of α-In 2 Se 3 , that providing a way for future design of bifunctional catalysts without precious metals based on two-dimensional ferroelectric substrate. • The effect of polarization for the HER and OER activity of Co atom supported on α-In 2 Se 3 has been investigated by DFT. • The activity of TM atom can be largely enhanced or optimized by electrostatic potential due to the polarization. • The stability of the single atom catalysts and the mechanism for enhancing catalytic reactions have been fully discussed. [ABSTRACT FROM AUTHOR]

The medium-Mn steels have a great application potential in the engineering fields due to its excellent strength and toughness. However, the presence of coarse martensite and segregation of Mn in the fusion-welded medium-Mn steel joint severely deteriorated toughness and ductility. In this work, 6 mm thick medium-Mn steel plates were joined by friction stir welding, and then were intercritically annealed to enhance the toughness and ductility of the joint. The as-welded nugget zone (NZ) contained lath martensite with low proportion of high angle boundaries (HABs), leading to the joint with lower elongation of 22.5% and the impact energy of 73.6 J/cm2. However, the as-annealed NZ consisted of ferrite and austenite because partial martensite changed to reversed austenite, while other martensite became ferrite during annealing. In addition, the proportion of HABs in the as-annealed NZ increased obviously. In comparison with as-welded joint, the impact energy and elongation of the as-annealed joint was increased by 70.7% and 44.4%, respectively. The abovementioned excellent mechanical properties were attributed to the high proportion of HABs and a large amount of ultra-fine reversed austenite with high thermal and mechanical stability, which provided a significant transformation induced plasticity effect, obviously inhibiting crack initiation and propagation. This systematic work provided a reference for welding similar materials containing retained austenite. [ABSTRACT FROM AUTHOR]

Hard β-Ta phase is generally produced during Ta film deposition. While in some cases, soft α-Ta phase is preferred to ensure deformation capability. In this work, templated growth strategy by introducing Cr buffer layer is proposed to tailor the phase composition in Ta films. A broad spectrum of β-Ta/α-Ta ratio from 90% to 0% can be continuously and precisely achieved when the buffer layer thickness is correspondingly controlled from 0 to ∼90 nm. Hardness of the Ta films is well proportional to the β-Ta/α-Ta ratio. The underlying mechanism of phase tailoring is rationalized by demonstrating the thickness-dependent crystallization of buffer layer. [Display omitted]. [ABSTRACT FROM AUTHOR]

The Al3+ doping effects on the ferromagnetic metallic state of La 0.55 Ca 0.45 MnO 3 have been studied by preparing the La 0.55 Ca 0.45 Mn 1- x Al x O 3- δ (x = 0, 0.05, 0.1, 0.15) ceramics. Various measurements such as ac susceptibility, relaxation, magnetization and resistivity were performed to study the magnetic and magnetotransport properties. The magnetic disorder produced by the Al3+ dopants and the oxygen vacancies suppress the long range ferromagnetic ordering and induce a short range charge ordered antiferromagnetic clusters, leading to a phase separated behavior in the Al3+-doped samples. A Griffith-like behavior is observed due to the occurrence of short range ferromagnetic clusters in the paramagnetic phase. The 15% Al3+ doping sample exhibits a spin-glass state. The 10% Al3+ doping system is blocked in a metastable state upon cooling at zero field, and a sharp metamagnetic transition is induced by applying a high magnetic field, in which the antiferromagnetic phase is transformed into ferromagnetic phase and the ferromagnetic clusters grow in size. The ferromagnetic domains grows rapidly when applying a high magnetic field. Once the conducting ferromagnetic domains are interconnected throughout the sample, a percolative insulating-to-metallic state transition would occur, accompanied by a sharp drop in resistivity. • Al3+ doping induces charge ordered AFM clusters in La 0.55 Ca 0.45 Mn 1- x Al x O 3- δ. • The magnetic disorder caused by Al3+ doping suppresses the long rang FM ordering. • The AFM clusters transform into FM phase via field driven metamagnetic transition. • Percolative insulator-metallic transition occurs when applying a magnetic field up to H C. [ABSTRACT FROM AUTHOR]

Ti alloy clad plate is of great interest for marine and petrochemical industry applications. However, high interfacial bonding is hardly obtained in the Ti alloy clad plate due to the brittle intermetallic compounds (IMCs) forming at the interface. In this study, a Ti-6Al-4V alloy/EH690 steel clad plate was fabricated by vacuum rolling and subsequently tempered to control the mechanical property of the steel substrate. The tempered sorbite appeared in the EH690 steel after quenching and tempering (QT). A decarburized zone, Fe 2 Ti + TiC mixed phases layer, and β-Ti layer were formed at the interface between steel and Ti. The brittle IMCs with high lattice mismatch resulted in a low interfacial strength of 108 MPa. To improve bonding strength, Nb was inserted between Ti and steel as an interlayer, which effectively inhibited the inter-diffusion of Ti, Fe, and C without brittle TiC or Fe-Ti IMCs. A (Ti, Nb) solid solution layer with high plasticity was present at the Nb/Ti interface. Fe 2 Nb and Fe 7 Nb 6 phases were detected at the steel/Nb interface, exhibiting less brittleness and hardness compared to Fe-Ti IMCs. The interfacial shear strength was up to 265 MPa after adding the Nb interlayer, showing a mixed fracture mode of brittleness and ductility. [ABSTRACT FROM AUTHOR]

Ti/Al clad plate is a highly promising material due to its low cost, lightweight nature, high strength, and excellent corrosion resistance. However, the deformation coordination between Ti and Al is very poor, and both metals easily are oxidated, resulting in a weak interfacial bonding. In this study, Ti/Al clad plate was fabricated by vacuum rolling, obtaining a clear interface without oxidation and compound. The as-rolled Ti/Al clad plate had a shear strength of 76 MPa with the fracture being at the Al substrate due to the solution of Mg 2 Si precipitates in the Al substrate during rolling. As a result, the solution and aging is necessary to enhance interfacial bonding. There were fine and dispersed Mg 2 Si precipitates in the as-treated Al substrate, and an (Al, Si) 3 Ti layer with ∼300 nm thickness appeared at the interface. Besides, the interfacial shear strength was up to 140 MPa, and the fracture still was at the Al side. The as-treated clad plate had an elongation of 33.5% which exceeded that of 25.8% calculated by the mixed rule. Obviously, the thin (Al, Si) 3 Ti layer is helpful to improve interfacial shear strength and plasticity of the Ti/Al clad plate. [ABSTRACT FROM AUTHOR]

Magnetron sputtering technique was employed to synthesize crystalline/amorphous high-entropy alloy (AHEA) X/AHEA (X = Cu and Ni, AHEA = Fe 20 Co 20 Cr 20 Ni 20 B 10 Si 10) nanostructured multilayers (CANMs) with equal layer thickness h ranging from 5 to 150 nm, aiming at systematically investigating their plastic deformation and microstructural evolution. Unlike traditional crystalline/crystalline multilayers often with shear banding at small h , the present X/AHEA CANMs exhibit h -independent homogeneous deformation via the thinning of both constituent layers, while associated with h -dependent deformation-induced devitrification in AHEA layers with thickness below 25 nm. This homogeneous plasticity of AHEA layers with the large incubation size for mature shear bands can be ascribed to the coupling between dislocations in X layers and shear transformation zones in AHEA layers. Meanwhile, the absorption of abundant dislocations emitted from X layers by AHEA layers with small thickness facilitates the occurrence of devitrification behavior, implying the microstructural instability under strong constraint conditions. Moreover, both of Cu/AHEA and Ni/AHEA CANMs manifest size-dependent hardness with the fashion that "smaller is stronger", which is captured well by the rule-of-mixture, based on the size-dependent strength of X nanolayers and size-independent homogenous flow of AHEA nanolayers. [Display omitted] [ABSTRACT FROM AUTHOR]

Hole machining of nickel-based alloys has a wide application space in aerospace manufacturing industry, but the high cutting force, high cutting temperature, large plastic deformation, cold work hardening and severe tool wear during the cutting process of nickel-based alloys make them typical difficult-to-machine materials. Therefore, when drilling nickel-based alloys, the selection of cutting parameters is very important. Reasonable cutting parameters will help to control the chip shape and facilitate chip removal. In this paper, the cutting force, cutting temperature, and tool life of high-speed steels in drilling Nickel-based superalloy Inconel 718 was investigated through orthogonal cutting experiments. Then the empirical method of multi-factor line regression was used to establish the empirical models of drilling torque, thrust force, cutting temperature, and tool life of the drills with emulsion as the cutting fluid, and to verify the validity of the established model, and the significance of the regression method is tested to verify the effectiveness of the model. The tool wear morphology and wear mechanisms were examined by scanning electron microscope (SEM) and energy spectrum analysis (EDS). The results revealed that the major drill wear modes incorporate flank wear, peripheral wear, micro-chipping and chipping, and the tool failure mechanisms were comprehensively synergistic interactions among abrasive wear, adhesive wear, and oxidation wear. In addition, the cutting parameters of high-speed steels in drilling Nickel-based superalloy were optimized based on the response surface methodology of equivalent tool life-efficiency, and then the reasonable cutting parameters under the condition of using cutting fluid were recommended. [ABSTRACT FROM AUTHOR]

Magnetization relaxation, ac susceptibility, dc magnetization and magnetoelectrical transport measurements have been carried out on Al3+-doped manganites La 0.5 Ca 0.5 Mn 1- x Al x O 3- δ (x = 0.05, 0.07, 0.09, 0.10, 0.15). Experimental results suggest that nonmagnetic Al3+ substituting Mn suppresses the ferromagnetic phase and induces a charge ordered antiferromagnetic phase. The coexistence and competition of these two kinds of interactions result in a spin-glass like state in x = 0.1 and 0.15 system. Obvious hysteresis was observed in both magnetization and resistivity versus temperature and magnetic field curves, suggesting an inhomogeneous metastable phase transition. Upon applying a magnetic field of H C A-F, the Al3+-doped samples undergo an irreversible metamagnetic transition from the charge ordering antiferromagnetic insulating to ferromagnetic metallic phase in the low temperature region. Phase diagram in the H C - T plane has been determined according to the magnetization and magnetoelectric transport measurements. The magnetic disorders and antiferromagnetic matrix produced by Al3+ dopants and spontaneous oxygen vacancies play an important role in the pinning of the FM phase. [ABSTRACT FROM AUTHOR]

A new kind of porous 6061 aluminum alloy composite material was successfully fabricated using self-made high-strength silicon-containing ceramic hollow spheres as reinforcement. For comparison, another composite with commercial alumina hollow spheres was produced. All of these porous composite materials were produced by sintering at 650 ℃ for 2 h. Their microstructures display that the aluminum alloy reacts with the self-made ceramic hollow spheres, forming a thin transition layer containing MgO and Al 2 O 3. Moreover, it was analyzed that the influence of the different classes of ceramic hollow spheres on the properties of porous composites, including the compressive strength, specific strength and energy absorption performance. The results indicate that the self-made silicon-containing ceramic hollow sphere can help to hinder the plastic deformation of the aluminum alloy metal matrix, which makes the sample display a short yield platform where the stress remains relatively stable. As a comparison, there is no yield platform where the stress remains relatively stable in the sample with commercial alumina hollow spheres under compression. Due to the formed transition layer, the sample with the self-made ceramic hollow sphere has a significantly higher compressive strength, specific strength and energy absorption performance. Compared with the porous magnesium alloy composite, the compressive behavior of porous composite is subject to that of the metal matrix to a great extent, and the content of Mg in the matrix determines the resultants and the level of the interface reaction. In addition, the compressive strength, specific strength, and energy absorption capacity of the porous aluminum alloy composite are all significantly higher than those of the porous magnesium alloy composite. • A new kind of porous 6061 aluminum alloy composite material was fabricated by using self-made ceramic hollow spheres with high strength. • The hollow sphere can react with the aluminum alloy to form a transition layer containing MgO and Al2O3 for hindering the plastic deformation. • The strength and energy absorption of the sample with this hollow sphere are much higher than those with commercial alumina hollow sphere. • The porous composite of aluminum alloy has more excellent mechanical properties than that of magnesium alloy, due to the alloy matrix. [ABSTRACT FROM AUTHOR]

• Prussian green ECD was prepared by one-step hydrothermal method. • ECDs can show three color conversions with a single layer electrochromic material. • More active sites and shorter K+ diffusion distance improve the performance of ECDs. • The evolution of Fe in the process of discoloration has been systematically studied. • The color of the film depends on the ratio of Fe3+/Fe2+ in the PB structure. Prussian green (PG) film was directly grown on FTO glass by one-step hydrothermal process for excellent electrochromic performance. The electrochromic devices (ECDs) based on as-grown PG film can show reversible color changes between green, blue and colorless states. The existence state of iron elemental in PG film at different color states was studied by X-ray photoelectron spectroscopy. Compared with the traditional Prussian blue ECDs, PG ECDs achieve a higher optical modulation range (42.7%) and a shorter switching time (t c /t b =1.0/7.4 s). This study provides a novel method for preparing high-performance three-color ECDs by a simple hydrothermal method, and clearly shows the evolution of Fe ions during the discoloration process. [ABSTRACT FROM AUTHOR]

• Fine uniformly dispersed broken precipitates were obtained by ECAP. • The dislocation and broken precipitated phase enhanced the uniform corrosion. • The corrosion rate of AA8176 was reduced at 0 °C with ECAP technology. Electrochemical tests and immersion experiments were employed to investigate the corrosion behaviors of the Al-Fe alloy (AA8176) processed by equal channel angular pressing (ECAP) in 3.5 wt% NaCl solution at different temperature (25 °C and 0 °C). It was worked out that after ECAP, with the reduction of grain size, the fragmentation and uniform distribution of precipitated phases increased the number of pitting corrosion but reduced its size, the increase of grain boundary density and the reduction of precipitated phase aggregation decreased the degree of intergranular corrosion. AA8176 changed from local corrosion to uniform corrosion, which provides a new idea to improve the corrosion resistance of Al-Fe alloys. [ABSTRACT FROM AUTHOR]

• The EVPSC-TDT model is used to mimic the stabilized stress-strain hysteresis loops of the rolled AZ31B plate under cyclic loading in different material orientations. • A threshold equation with a new parameter is proposed to constrain fresh twinning and retwining during cyclic loading. • The equation proposed in the literature is used to describe the evolution of residual twinning during cyclic loading. • The effect of initial CRSS of detwinning on plastic response during reverse loading is investigated. • The detwinning-induced inelastic behavior is predicted to occur at the very end of the unloading process for the 90° material orientation. The EVPSC-TDT model is employed to mimic the stabilized stress-strain hysteresis loops of the rolled AZ31B plate under cyclic loading in different material orientations. The predicted stabilized stress-strain hysteresis loops for different material orientations are generally in good agreement with the corresponding experimental data. The key features associated with twinning and detwinning are interpreted in terms of activities of deformation modes. To appropriately mimic the cyclic plastic response of the rolled AZ31B plate, cyclic loading experiments should also be accounted for in determining the Voce-type hardening law parameters in the current model. The equation proposed in the literature is used in the current model to describe the evolution of residual twinning during cyclic loading, and a threshold equation with a new parameter is proposed to constrain fresh twinning and retwining. The effects of parameters in the two equations on cyclic plastic response are investigated. To approximately describe the apparent easier reverse motion of twin boundaries, the initial CRSS of detwinning is set to be half of that of twinning, and for simplicity the other voce-type hardening law parameters are kept the same for both twinning and detwinning. The effect of initial CRSS of detwinning on plastic response during reverse loading is also investigated. The inelastic behavior is predicted to occur at the very end of the unloading process for the 90° (ND) material orientation, which is ascribed to detwinning. It is assumed that the magnitude of internal tensile stress upon unloading together with that of the activation stress for detwinning determine when or whether detwinning will occur during unloading. The discrepancies between numerical simulations and experiments of the pseudo-elasticity behavior might be because the current mean field model based on self-consistent schemes might not properly describe some microstructure related properties of the AZ31B plate and so underestimates the internal tensile stresses of twinned grains before unloading, which deserves further investigation. [ABSTRACT FROM AUTHOR]

In this study, the crystallography of the nugget zone of bainitic steel was examined by applying friction stir welding (FSW) and submerging in various cooling mediums. In air, the variants mainly occurred in a single Bain group because of the plastic accommodation of transformation strain. However, in water and a mixture of water and CO 2 , the variants generated in two and four close-packed (CP) groups, respectively, and this was attributed to the self-accommodation of transformation strain. In this case, the variant selection was inhibited by both the severe deformation during FSW and low temperature of cooling medium. Furthermore, the reduced cooling-medium temperature resulted in refined bainitic and martensitic blocks with an increased fraction of high-misorientation variant pairs owing to the increased transformation driving force. • Previous studies on the FSW bainitic steel were focused on the phase transformation, and the crystallography was ignored. • The crystallographic characteristics and its effect on microstructure refinement for FSW bainitic steel was studied. • In air, the plastic deformation in austenite easily accommodates the transformation strain, causing the variant selection. • In water and water+CO 2 , refined blocks were obtained with an increased fraction of high-misorientation variant pairs. [ABSTRACT FROM AUTHOR]

The precipitate evolution, strength and corrosion resistance of an Al–Zn–Mg–Cu alloy processed by cryorolling, warm rolling and final aging have been investigated. A large number of spherical Zn-rich GP zones formed after warm rolling. In-situ transmission electron microscopy (TEM) observation indicated that the GP zones are stable during aging treatment and can serve as nuclei for subsequent precipitates, leading to homogeneous distribution of precipitates in the matrix after aging. TEM results also showed that ultrafine subgrains were developed in the deformed microstructure during aging. The high density of precipitates and dislocations combined with grain refinement contribute to the higher strength of the thermo-mechanically treated alloy compared with the peak-aged alloy. On the other hand, the η phase with C15 cubic structure having ‧‧‧RR‧‧‧ stacking is found in the thermo-mechanically treated alloy and is different from one with C14 hexagonal structure having ‧‧‧RR−1‧‧‧ stacking that is commonly observed in conventionally aged alloys, where R and R−1 represent rhombic layer and the relatively 180°-rotated rhombic layer, respectively. The transition from ill-defined stacking to C15 stacking and further to C14 stacking is observed in the structure of a η phase. Besides, the combination of warm rolling and aging can avoid the formation of continuous grain boundary precipitates, which is beneficial to the corrosion resistance of the alloy. [ABSTRACT FROM AUTHOR]

The effect of grain boundary character distribution (GBCD) on hydrogen-induced cracks (HICs) initiation and propagation in nickel-saving austenitic stainless steel was investigated at different strain rates with electrochemical hydrogen charging. The fracture strength and elongation of specimens decreased as the strain rates decreased due to more hydrogen atoms being transported by mobile dislocations. HICs are more likely to initiate at random grain boundaries (RGBs) because of poor deformation coordination of adjacent grains at RGBs after hydrogen charging. Special boundaries (SBs) deflected HICs and hindered the propagation of HICs owing to a more stable boundary structure and less strain localization during slow strain rate tensile (SSRT) deformation with hydrogen charging. Furthermore, highly efficient distributions of SBs contribute to great resistance to hydrogen embrittlement. • Higher content of SBs reduced the elongation and strength degeneration of material after H-charging. • With the increase of SB, the fracture mode changes from intergranular to quasi-cleavage. • SBs are beneficial to delay hydrogen permeation. • HICs prefer to initiate on RGBs due to poor deformation coordination after H-charging. • HICs are deflected and terminated by special boundaries, a higher fraction of f J2 /(1-f J3) effectively inhibit HICs propagation. [ABSTRACT FROM AUTHOR]

In this work, the self-ion irradiation behavior of nanocrystalline copper-tantalum alloys was investigated. In particular, the microstructural evolution of Cu-3at.%Ta and Cu-10at.%Ta was evaluated under the fluence of 2 × 1017 ions/cm2 of 4 MeV Cu-ions at different temperatures. Results revealed that despite the ability of Cu-10Ta to reprecipitate new nanoclusters and thereby increase the sink density by ∼17%, it undergoes significant microstructural evolution. On the other hand, Cu-3Ta exhibits a relatively more stable microstructural response and 3.5 times less swelling over the same conditions. This result illustrates the premise that irradiation and deformation may be coupled to stabilize/rejuvenate Ta-nanoclusters in extreme-environments. [Display omitted] [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the effects of glutamine (Gln) on the growth performance and immune function of high-concentrate fattening lambs. Thirty 3-month-old male healthy Hu sheep with a similar body weight of 26.75 ± 0.65 kg were randomly selected and assigned to 3 groups with 10 lambs per group. Lambs in 3 groups were fed basic diets supplemented with 0 (control group, fed a high-concentrate diet), 0.5% (Gln1, fed a high-concentrate diet), or 1.0% (Gln 2, fed a high-concentrate diet) Gln. The pre-experimental period lasted for 15 days, and the experimental period lasted for 45 days. The obtained results showed that compared with the CON group, the Gln group showed a lower F/G from 16 to 30 d, 31–45 d, and 0–45 d (P < 0.05); increased heart weight, heart index, spleen weight, spleen index, thymus weight, thymus index, small intestine weight, and small intestine index on day 45 (P < 0.05); increased concentration of CD4+ and CD8+, CD4+/CD8+ T lymphocyte ratios, lymphocyte transformation ratio in peripheral blood, and IgG content and IL-2 ratio in plasma (P < 0.05); decreased apoptosis ratio in peripheral blood on days 15, 30, and 45 (P < 0.05). However, there was no difference in these parameters compared to the Gln group (P > 0.05). In summary, this study showed that dietary Gln supplementation may improve the immune function of lambs by providing energy to the proliferation of T cells. • Gln group showed a lower F/G from 16 to 30 d, 31–45 d, and 0–45 d (P < 0.05), increased the organ index of heart, spleen, thymus, and small intestine on the 45 days (P < 0.05). • The inclusion of Gln showed increased the CD4+ and CD8+ concentration, the CD4+/CD8+ T lymphocyte ratios, the peripheral blood lymphocytes transformation ratio, and the serum IgG and IL-2 levels (P < 0.05), and decreased the peripheral blood apoptosis ratio on the 15, 30, and 45 days (P < 0.05). • These results suggest that dietary Gln supplementation might improve the immune function of lamb by providing energy to the proliferation of T cells. [ABSTRACT FROM AUTHOR]

Misfit dislocation arrays (MDAs) at semi-coherent heterogeneous interface have been demonstrated effectiveness to trap and then outgas helium (He) for alleviating void swelling in metals, but limited by atomic-level thin film deposition that is difficult to scale-up for industrial production. In this work, we proposed an innovative strategy that could generate semi-coherent homophase interfaces in a same grain by varying surface energy density assisted by high-temperature graphene (Gr) deposition. This strategy transforms strain energy and surface energy, two originally distinctive processes into successive processes, and demonstrates experimentally and theoretically by introducing {111} copper (Cu) in a {100} Cu grain. Subsequent He implantation and electrical resistivity measurement results suggest that high-density MDAs originated at this {111}/{100} interface could form stable He nanochannels near Cu surface with Gr assistance, manifesting by ultra-low increased ratio of the electrical resistivity (i.e. ∼3800% of Cu vs. ∼90% of Gr/Cu) after He implantation. The present findings may provide a new strategy for efficiently managing He and achieving surface protection of advanced metals, merely by depositing a super-rigid material on metal surface to greatly reduce surface energy density. [Display omitted] [ABSTRACT FROM AUTHOR]

The 12Cr1MoWV (wt%) ferritic/martensitic steel HT9 is a candidate material for fuel cladding in advanced nuclear reactors, such as the Versatile Test Reactor currently under development. As such, understanding the relationship between microstructure and mechanical properties in the context of irradiation environments for these steels is critical. N content, and more specifically interstitial N, has been hypothesized to be detrimental to irradiated properties at lower temperatures (less than 0.3T m) to a total of 6 dpa; however, in this work at a dose of 1 dpa the irradiated microstructure was improved with added N, leading to less irradiation hardening. Three variants of HT9 were irradiated with 1.5 MeV protons to a dose of 1 dpa at 300 ˚C. The HT9 variants included Low (10 ppm), Mid (190 ppm), and High (440 ppm) N alloys that were otherwise nearly identical. Changing the N content had a variety of effects on the irradiated defect structures. As N content increased, the average dislocation loop diameter decreased, while the number density of loops increased. Additionally, extensive Ni clustering was observed on dislocations and interfaces. The Mid and High N specimens exhibited significantly less hardening (ΔHV ≅ 100) relative to the Low N specimen (Δ HV ≅ 160). The decrease in hardening is attributed to vanadium carbonitride acting as a sink for Ni clusters that would otherwise form on dislocations. Under the irradiation conditions used, these results suggest increasing the N content in HT9 may have a desirable effect on the irradiated structure and properties at the dose studied, as well as the swelling resistance at higher doses. In other words, N content appears to be a powerful tool for tailoring the self-interstitial atom cluster mobility in F/M steels for different temperature and dose applications. [ABSTRACT FROM AUTHOR]

• Fatigue behavior of Cu films on wrinkled PDMS substrates is investigated. • Wrinkled surfaces significantly enhance fatigue resistance of Cu films. • Buffering of wrinkle structures inhibit the crack initiation. • Surface undulations suppress the crack propagation. • Fatigue resistance exhibits film thickness and strain amplitude effects. The fatigue behavior of nanocrystalline Cu films on polydimethylsiloxane (PDMS) substrates was studied. It is revealed that the Cu films on wrinkled PDMS substrates exhibit ultrahigh fatigue resistance without electrical failure. The electrical resistance either remains constant during cyclic loading or slightly increases and rapidly reaches saturation, which is attributed to the buffering effect of wrinkle structures on crack initiation and the suppression effect of surface undulations on crack propagation. The film thickness-dependence of fatigue resistance is sensitive to the amount of the strain amplitude. The fatigue resistance increases with decreasing film thickness at small strain amplitudes because of higher strength and smaller local strain concentration, while the fatigue resistance first increases and then decreases as the film thickness increases at large strain amplitudes, which is related to the extrinsic deformation capability of Cu films. [ABSTRACT FROM AUTHOR]

In this work, a nanocrystalline (NC) Cu-10at.%Ta alloy is irradiated with helium at different temperatures to assess the stability and effectiveness of Ta nanoclusters in trapping helium and suppressing swelling. Advanced microstructural characterization of the room-temperature irradiated specimens indicated the presence of small He-bubbles (∼1-2 nm) at the peak damage depth mainly at the core and along the interface of Ta nanoclusters with Cu matrix. Few bubbles were found along grain boundaries, with much smaller bubbles homogenously distributed within the copper lattice. High-temperature irradiation exhibited bubbles of ∼3-5 nm, which were primarily associated with nanoclusters as compared to other locations, with no observed faceting of the bubbles. Atom probe analysis confirmed helium partitioning to the Ta nanoclusters indicating the effective entrapment of these He atoms. [Display omitted] [ABSTRACT FROM AUTHOR]

• Stretchability of Cu films on wrinkled PDMS substrates is investigated. • Wrinkling structures significantly enhanced stretchability of Cu films. • Effect of film thickness and wrinkle size on fracture strain is reported. • Fracture strain evolves in a non-monotonic manner for smaller wrinkles. • Fracture strain monotonically increases for larger wrinkles. Stretchable electronics demand that the metal thin film electrodes have the capacity to experience large level of strains without obvious changes in electrical performance. This work investigated the effect of film thickness and wrinkle dimension on the stretchability of Cu films on polydimethylsiloxane substrates. It is revealed that the wrinkle dimension highly depends on the ultraviolet/ozone treatment time. The fracture strain increases until reaching a maximum and then decreases with increasing film thickness for smaller wrinkles. By contrast, the fracture strain monotonically increases as the film thickness increases for the larger wrinkles within the thickness range studied. Generally, the larger wrinkle dimension leads to a higher fracture strain for a given film thickness. The evolution of fracture strain can be rationalized in terms of the competition between the intrinsic stretchability of Cu films related to the grain size and the extrinsic strain concentration related to film thickness and wrinkle dimension. [ABSTRACT FROM AUTHOR]

The heavy-ion irradiation behavior of bulk zirconium-niobium multilayered composites was investigated up to large doses. Multilayers with an average individual layer thicknesses ranging between 15 and 80 nm were synthesized by accumulative roll bonding technique. The irradiation was performed with a defocused 7 MeV Zr2+ ion beam at 500 °C. The maximum dose achieved was ∼145 dpa at the depth of ∼1.5 μm from the irradiated surface. Sub-surface microstructural damage and the chemical redistribution were characterized by transmission electron microscopy and energy dispersive spectroscopy, respectively. Irrespective of the layer thicknesses, the irradiation condition caused layer instability and the extent of damage varied with the dose levels. Doses lesser than ∼60 dpa caused layer fragmentation and greater than ∼60 dpa resulted in layer dissolution. The chemical mixing of layers occur to a depth of ∼1 μm, consuming multiple bi-layer periods. Despite the elevated irradiation temperature (500 °C) and a slightly positive heat of mixing (+6 kJ/mol), no phase separation was observed and single-phase was retained in the mixed region. The results demonstrate that chemical mixing was facilitated by the liquid phase miscibility of Zr and Nb, which propelled the interdiffusion within the thermal spikes towards mixing. [ABSTRACT FROM AUTHOR]