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To improve the wear resistance of the inner wall of hydraulic support columns, Fe-based coatings X1, X2 and X3 were prepared on the inner wall of a hydraulic support column using laser cladding technology with three different Ni-content Fe-based alloy powders. The microstructure, mechanical properties and tribological performance of these coatings were analyzed using metallographic microscope, 3D confocal surface topography instrument, universal testing machine and high-speed reciprocating friction and wear testing machine. Results showed that three coatings were homogeneous and compact, and had good metallurgical bonding with the substrate. The cladding layers were mainly composed of α-Fe with a BCC structure and a(Fe-Cr) solid solution, with the formation of a(Fe-Cr-Ni) phase in the X2 and X3 cladding layers. Among the three coatings, the tensile strengthes of X1, X2 and X3 were 563, 597 and 470 MPa, respectively, with X2 having the highest tensile strength. The wear rates of the three coatings were all lower than that of the substrate, with the wear rate of the substrate being approximately eight times that of the X2 coating. The wear mechanism of the substrate was primarily dominated by adhesive wear and abrasive wear, while the wear mechanism of the coatings was mainly abrasive wear.

The influence of austenitizing temperature and isothermal transition temperature on the mechanical properties and splitting characteristics of C70S6 were investigated. The maximum ultimate tensile strength and yield strength were 1032 and 625 MPa, respectively, when the lamellar spacing of sorbite was 0.195 μm. The greatest elongation was 17% when the size of the pearlite colony was 13 μm, which suggested an approach for enhancing the properties of pearlite steel at a low cost. The splitting property performed excellent when the proeutectoid ferrite content is 0.3%, the prior austenite grain is 38.9 μm, and the yield ratio is 0.57 currently. The connection between the process performance and the microstructure parameters was established, allowing process improvement to be guided accurately. Highlights: A functional model exploiting the potential mechanical properties of F + P forging steels C70S6 was proposed.The combined action of less proeutectoid F and larger PAG could obtain better splitting characteristics.The connection between the process performance and the microstructure parameters was established. [ABSTRACT FROM AUTHOR]

This study analyzes the influence of different ultrasonic amplitudes on the microstructure composition, microhardness, tensile strength, and corrosion resistance of Al alloy/steel laser welding-brazing joints assisted by ultrasonic vibration. The application of ultrasonic vibration did not change the microstructure composition of the joints but refined them. The joints were all composed of θ-Fe(Al, Si)3 and τ5-Al7.2Fe1.8Si formed at the interface reaction zone, as well as an α-Al solid solution and Al-Si eutectic phase generated in the weld seam zone. Meanwhile, the thickness of the IMCs at the interface decreased with an increase in the ultrasonic amplitude. When the ultrasonic amplitude was 8 μm, the IMCs thickness was a minimum of 1.62 μm. In this condition, the reduction of the IMCs thickness and the refined grain of joints made the microhardness and tensile strength reach the maximum. The fracture of joints with ultrasonic amplitudes of 0 and 4.8 μm began at the weld seam and extended to the interface reaction zone at the steel side, while the fracture of joints was located in the heat-affected zone (HAZ) of the Al alloy side when the ultrasonic amplitude was 8.0 and 11.2 μm. The fracture mode of the former presented a typical mixed fracture with cleavage steps and tearing edges, and that of the latter showed ductile fracture with uniform and fine ductile dimples. The corrosion resistance of the joints was improved by adding ultrasonic vibration. When the ultrasonic amplitude was 8 μm, its corrosion resistance was optimum; it was ascribed to a dense oxide film formed on the surface of the metal under the action of ultrasonic vibration. [ABSTRACT FROM AUTHOR]

As the inner working surface of a diesel engine, the cylinder liner is subjected to a harsh frictional wear environment, which can lead to performance degradation and ultimately affect the engine's service life. Ceramic coatings can improve the wear resistance of the cylinder liner, thereby enhancing the reliability and stability of the diesel engine. In this study, Cr 2 O 3 –Y 2 O 3 ceramic composite coatings were deposited on the substrate of 304 stainless steel by atmospheric plasma spraying (APS). The influence of Y 2 O 3 content on the microstructure, porosity, phase composition, microhardness and wear performance of the composite coating was investigated. The results showed that the composite coatings exhibited a typical layered structure, and Y 2 O 3 and Cr 2 O 3 were dispersed relatively evenly. When the Y 2 O 3 content was 10 %, the coating had the lowest porosity rate of 5.41 % and the highest hardness of 1094.6 HV 1. As the Y 2 O 3 content increased, the coating exhibited an increase in porosity and a decrease in hardness. Under dry friction conditions, the friction coefficient curve underwent a rapid increase phase, followed by stabilizing within the range of 0.29–0.40. When the Y 2 O 3 content is 10 %, the coating exhibits the best wear resistance, including the lowest coefficient of friction, wear rate, and scratch depth. However, the composite exhibits the worst wear resistance when the Y 2 O 3 content reaches 50 %. The wear mechanism was altered by the addition of Y 2 O 3. At lower Y 2 O 3 content, the predominant wear mechanism was abrasive wear resulting from particle refinement. Conversely, at higher content, adhesive wear caused by wear transfer from the milling balls became more prominent. [ABSTRACT FROM AUTHOR]

Ni-Mo-ZrO2 composite coatings with a thickness ranging from 6.9 to 8.7 µm were obtained by direct-current electrodeposition from a bath comprising nickel sulfate and sodium molybdate as main salts, and ZrO2 nanoparticles as ceramic phase. The effect of mass concentration of ZrO2 on the microstructure, mechanical properties, and corrosion resistance of Ni-Mo-ZrO2 composite coating was studied. The results showed that the mass fraction of ZrO2 in composite coating was increased with the increasing of mass concentration of ZrO2 in bath, while the surface morphology, wear resistance, and corrosion resistance got better initially and then worse, and the nanohardness was increased at first and then decreased. The composite coating electrodeposited with 10 g/L of ZrO2 exhibited the best corrosion resistance, while the one electrodeposited with 20 g/L of ZrO2 featured the best microstructure and mechanical properties. [ABSTRACT FROM AUTHOR]

Electromigration is one of the most important research issues affecting the reliability of solder joints. Current-induced Joule heating affects the electromigration behavior of solder joints. Solder joints with different cross-sectional areas were designed to obtain different Joule heating properties. The effects of the interfacial intermetallic compound (IMC) and mechanical properties of Sn58Bi/Cu solder joints were studied for different Joule heating properties. The results showed that as the cross-sectional area of the Sn58Bi/Cu solder joints increased, the Joule heating of the joint increased. The anode IMC thickness of the joint thickened and transformed into a planar shape. The Bi migrated to the anode region to form a Bi-rich layer and gradually increased in thickness. The cathode IMC thickness first increased, then decreased, and gradually dissolved. The Sn-rich layer formed near the solder side and gradually increased in thickness, with microcracks occurring when the cross-sectional area of the joint increased to 0.75 mm2. The joint shear fracture path moved from the soldering zone near the cathode IMC layer to the interfacial IMC layer. The fracture mechanism of the joint changed from a mixed brittle/tough fracture, dominated by deconstruction and secondary cracking, to a brittle fracture dominated by deconstruction. The joint shear strength was reduced by 60.9% compared to that in the absence of electromigration. [ABSTRACT FROM AUTHOR]

The distribution of the dendrite arrays and the primary dendrite arm spacing (PDAS) in large-sized single-crystal superalloy blade was investigated by Voronoi tessellation. The dendrite arrays were hexagonal at the airfoil center and random at the trailing edge. The PDAS was gradually increased from the leading edge (about 370 μm) to the trailing edge (about 500 μm). With the solidification distance increasing, the PDAS in large-sized blade was decreased (about 380 μm) at the middle blade. [ABSTRACT FROM AUTHOR]

Fine-grained tailings have poor permeability and a long consolidation time, but treatment with flocculants can improve their mechanical properties. Changes in the physical and engineering properties of fine tailings due to treatment with different flocculants was investigated by microscope observations, settling tests and tests for shear strength, consolidation and permeability. A new concept – the relative flocculation rate Fr – was used to quantify the effect of flocculation on the hydraulic conductivity and void ratio of coarse tailings, fine tailings and flocculant-treated tailings under high pressure using a developed high-stress permeability and consolidation apparatus. The results showed that a composite flocculant could have a considerable effect on the geotechnical properties of fine tailings due to changes in the double diffusion layer (DDL) of the particles. However, for a consolidation pressure greater than 2 MPa, the DDL theory is no longer applicable. [ABSTRACT FROM AUTHOR]

To assess the individual and synergistic effects of 2-butyne-1,4-diol (BD) and chloride ions on the microstructure and residual stress of electrodeposited nickel, various nickel layers were prepared from sulfamate baths comprising varying concentrations of BD and chloride ions by applying direct-current electrodeposition. And their surface morphologies, microstructure, and residual stress were tested using SEM, XRD, EBSD, TEM, and AFM. While the nickel layers composed of pyramid morphology were prepared from additive-free baths, the surface flattened gradually as the BD concentration of the baths was increased, and the acicular grains in the deposits were replaced with <100> oriented columnar grains or <111> oriented nanograins; additionally, the residual tensile stress of the deposits increased. The addition of chloride ions to the baths containing BD significantly increased the residual stress in the nickel layers, although it only slightly promoted surface flattening and columnar grain coarsening. The effects of BD and chloride ions on the growth mode and residual stress of nickel deposits were explained via analysis of surface morphologies and microstructure. And the results indicate that the reduction of chloride ion concentration is a feasible way to reduce the residual stress of the nickel deposits when BD is included in the baths. [ABSTRACT FROM AUTHOR]

The aim of this study is to fabricate high-strength steel with exceptional yield strength and superior ductility by employing a novel design approach of nanolamellar/equiaxial crystal "sandwich" heterostructures, utilizing rolling and electron-beam-welding techniques. The microstructural heterogeneity of the steel is manifested in the phase content and grain size, ranging from nanolamellae comprising a small quantity of martensite on both sides to the completely coarse austenite in the center, which are interconnected via gradient interfaces. The structural heterogeneity and phase-transformation-induced plasticity (TIRP) offer remarkable strength and ductility for the samples. Furthermore, the synergistic confinement of the heterogeneous structures leads to the formation of Lüders bands, which exhibit stable propagation under the TIRP effect and impede the onset of plastic instability, ultimately resulting in a significant improvement in the ductility of the high-strength steel. [ABSTRACT FROM AUTHOR]

To solve the electromigration problem of micro−electronic connection solder joints, an ideal electromigration tester was designed, and the thickness of the intermetallic compounds (IMCs), average void diameter, grain orientation, failure, shear strength, and fracture path of Sn2.5Ag0.7Cu0.1RE0.05Ni−GNSs/Cu solder joints under constant−temperature electromigration were studied. The results indicate that the solder joints show evidence of typical electromigration polarity in the asymmetric growth of interfacial IMCs on the anode and cathode sides under the conditions of a current density ≥7 × 103 A/cm2 and an included angle between the c−axis of the β−Sn grains and the current direction θ ≤ 53.2°. The anode−side interfacial IMC is dominated by a Cu6Sn5 phase with a gradually increasing thickness, forming a Cu3Sn phase and showing evidence of microcracks. The Cu6Sn5 phase of the cathode−side interfacial IMC is gradually completely dissolved, and the growth of the Cu3Sn phase is accompanied by the formation of Kirkendall voids. The anisotropic diffusion of Cu atoms in the β−Sn of the micro−solder joints causes increased solder joint resistance and reduced shear strength. The shear fracture path of the solder joints moves from the cathode side near the IMC solder seam to the Cu3Sn interface. The shear fracture mechanism changes from ductile transgranular fracture dominated by β−Sn dimples to brittle fracture dominated by interfacial IMC cleavage and slip steps. [ABSTRACT FROM AUTHOR]

The cold metal transfer (CMT) welding-brazing process was chosen to join Al alloy and Ni-coated steel using AlSi12 as the filler wire. The macrostructure and microstructure of the joints were tested by using an optical microscope (OM), scanning electron microscope (SEM), energy dispersive spectrometry (EDS), and X-ray diffraction (XRD). The tensile properties and corrosion properties of the joints were also tested. The results showed that Ni coating could improve the wettability and spreadability of molten AlSi12 filler metal on the steel surface, resulting in a good appearance for the Al alloy/steel joint. Ni coating could hinder the chemical metallurgical reaction between Al atom and Fe atoms to inhibit the formation of brittle Fe-Al intermetallic compounds (IMCs) and reduce the thickness of the IMCs layer. Meanwhile, the Ni atom reacted with the Fe and Al atoms to form Al3Ni2, (Fe, Ni) Al3 and (Fe, Ni)2Al3, which improved the tensile strength of the joints. All joints with Ni coating cracked near the Al alloy. When the Ni-coating thickness was 5 μm, the tensile strength of the joint reached a maximum of 202.5 MPa. The addition of Ni could also improve the corrosion resistance of the joints. Significantly, when the Ni-coating thickness was 10 μm, most of the Ni coating was still solid, and the interface reaction layer was mainly composed of α-Ni solid solution and some (Fe, Ni)2Al3. [ABSTRACT FROM AUTHOR]

The catalytic oxidation of volatile organic compounds (VOCs) is considered a feasible method for VOCs treatment by virtue of its low technical cost, high economic efficiency, and low additionally produced pollutants, which is of important social value. Single-atom catalysts (SACs) with 100% atom utilization and uniform active sites usually have high activity and high product selectivity, and promise a broad range of applications. Precise regulation of the microstructures of SACs by means of defect engineering, interface engineering, and electronic effects can further improve the catalytic performance of VOCs oxidation. In this review, we introduce the mechanisms of VOCs oxidation, and systematically summarize the recent research progress of SACs in catalytic VOCs total oxidation into CO2 and H2O, and then discuss the effects of various structural regulation strategies on the catalytic performance. Finally, we summarize the current problems yet to be solved and challenges currently faced in this field, and propose future design and research ideas for SACs in catalytic oxidation of VOCs. [ABSTRACT FROM AUTHOR]

The microstructure of 3D five-directional braided composites (5DBCs) comprises the following three constituents: yarn, matrix and interface. The interface is the bridge between yarn and the matrix, and it controls the mechanical properties of composites. In this paper, a meso-scale finite element (FE) model containing an interface is proposed to analyze the off-axial tensile behavior of 5DBCs. Hashin criteria and maximum stress criteria with a gradual degradation scheme are employed to capture the damage evolution behavior of yarn and the matrix; zero-thickness cohesive elements ruled by a bilinear traction–separation constitutive relation are applied to simulate the interface debonding. These constitutive models are coded into a user-defined material subroutine VUMAT and implemented to attain a numerical solution based on ABAQUS/Explicit solver. The meso-scale FE model is verified with available experimental data in the on-axial loading condition and then utilized to predict the mechanical response in diverse off-axial tensile cases. The damage evolution process of a 5DBC specimen under typical off-axial loading is provided, and the corresponding failure mechanism is analyzed in detail. This work provides a transferable approach for numerical study on the interface and off-axis load problems in other textile composites. [ABSTRACT FROM AUTHOR]

The mechanical properties of nanocrystalline pure Ni films are degraded due to grain coarsening with exposure for a long time in ambient. In order to further improve the mechanical properties of Ni-based thin films, as-sputtered Mo-W co-doped Ni/Ni3Al multilayered structures were constructed. When the individual layer thickness (h) is lower than 40 nm, both the average grain sizes and the crystallinity degrees are degraded, showing a tendency for the formation of the amorphous phase. With h = 40 nm, nano-twins were observed as (111) twining interfaces for the multilayers due to the reduction of the stacking fault energy by the co-doping of Mo-W, whereas the nucleation and growth of the nano-twins were limited, without observations for the Mo-W co-doped Ni/Ni3Al multilayer with h = 10 nm. The hardness of the multilayers was enhanced, and the elastic modulus was reduced at a lower h, owing to the grain refinements and layer interface barriers for strengthening, and the existence of the amorphous phase with the inferior modulus, respectively. The resistance against the fracture was enhanced due to toughening by the lamellar structure for the Mo-W doped Ni/Ni3Al multilayer at h ≤ 40 nm. Comprehensively, the Mo-W-doped Ni/Ni3Al multilayer with 10 nm displays a superior mechanical performance. [ABSTRACT FROM AUTHOR]

Single‐photon emitters (SPEs) can play an important role in future quantum optics. Hexagonal boron nitride (h‐BN), a layered insulator (bandgap ≈6 eV), is a promising candidate for next‐generation SPEs because of its chemical and thermal stability and high brightness at room temperature. In this review, the microstructures (atomic defects, deformations, and cavities) of h‐BN are established and their SPE characteristics are analyzed. Recent progress in the synthesis of high‐quality bulk h‐BN, monoisotopic h‐BN, and epitaxial h‐BN films is also demonstrated. Some approaches for achieving SPE arrays are further discussed and the applications of h‐BN SPEs in the quantum field are investigated. The success in the preparation of large‐scale h‐BN and its microstructural engineering provides a promising future in low‐dimensional quantum optics. [ABSTRACT FROM AUTHOR]

Adding alloy elements to develop excellent properties in Al alloy/steel welding–brazing joints to realize lightweight vehicle structures has become a feasible task. Here, CMT welding–brazing was used to realize the reliable connection of Al/steel with a Cu coating. Al alloy/steel welding–brazing joints with different thicknesses of Cu coating were designed to study the influence of Cu on microstructure composition, mechanical properties and corrosion resistance. Then, the action rule of the Cu element on the interfacial microstructure evolution was clarified. The results showed that the appropriate Cu coating could effectively inhibit the reaction of Al and Fe and reduce the thickness of interfacial brittle intermetallic compounds (IMCs). Moreover, Cu could react with Al, Fe and Si to promote the formation of the τ5-Al7.2(Cu,Fe)1.8Si phase and control the formation of the brittle θ-Fe(Al,Si)3 phase, which improved the toughness of IMCs. When the thickness of the Cu coating on the surface of steel was 10 μm, the tensile strength of the Al alloy/steel CMT welding–brazing joint reached a maximum of 138.7 MPa and the corrosion resistance of the joint reached the optimum level. However, when the thickness of the Cu coating increased to 20 μm, the IMCs' thickness at the interface of the joint reached the minimum, but Cu reacted with Al to form a brittle Al2Cu phase under the higher Cu content, which deteriorated the tensile strength and corrosion resistance of joints. This work will provide an experimental and theoretical basis for developing good properties in Al/Cu-coating/steel welding joints. [ABSTRACT FROM AUTHOR]

To enhance the friction and wear properties of 40Cr steel's surface, CoCrFeMnNi high-entropy alloy (HEA) coatings with various Ti contents were prepared using laser cladding. X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) were used to characterize the phase composition, microstructure, and chemical composition of the samples. The findings demonstrated that the CoCrFeMnNiTix HEA coatings formed a single FCC phase. Fe2Ti, Ni3Ti, and Co2Ti intermetallic compounds were discovered in the coatings when the molar ratio of Ti content was greater than 0.5. The EDS findings indicated that Cr and Co/Ni/Ti were primarily enriched in the dendrite and interdendrite, respectively. Ti addition can effectively enhance the coating's mechanical properties. The hardness test findings showed that when the molar ratio of Ti was 0.75, the coating's microhardness was 511 HV0.5, which was 1.9 times the hardness of the 40Cr (256 HV0.5) substrate and 1.46 times the hardness of the CrCrFeMnNi HEA coating (348 HV0.5). The friction and wear findings demonstrated that the addition of Ti can substantially reduce the coating's friction coefficient and wear rate. The coating's wear resistance was the best when the molar ratio of Ti was 0.75, the friction coefficient was 0.296, and the wear amount was 0.001 g. SEM and 3D morphology test results demonstrated that the coating's wear mechanism changed from adhesive wear and abrasive wear to fatigue wear and abrasive wear with the increase in Ti content. [ABSTRACT FROM AUTHOR]

Optimizing the heat treatment procedure with 13 mm diameter 38Si7 spring steel is critical for developing high-performance, low-cost, large spring steel for railway clips. The effects of quenching temperature, holding time, tempering temperature, and tempering time on the microstructure and mechanical properties were investigated using an orthogonal experiment, designed with four factors and three levels. The best heat treatment settings were explored, as well as the variation laws of mechanical properties, decarburization behavior, and fracture morphology. The results demonstrated that quenching temperature and tempering temperature had the most impact on plasticity and tempering temperature, while time had the most effect on strength. The optimized heat treatment schemes made the elongation increase by up to 106% and the reduction in area increase by up to 67%, compared with the standard BS EN 10089-2002, and there were mixed fractures caused by ductility and brittleness. The fracture tests showed a good performance of 20.2 GPa·%, and the heat treatment processes' minimum decarburization depth of 93.4 μm was determined. The optimized process would obtain stronger plastic deposition and better decarburization performance. The microstructure was simply lightly tempered martensite, and the matrix still retained the acicular martensite. The optimal heat treatment process is quenching at 900 °C for 30 min (water cooling), followed by tempering at 430 °C for 60 min (air cooling). The research led to a solution for increasing the overall mechanical characteristics and decreasing the surface decarburization of 38Si7 spring steel with a diameter of 13 mm, and it set the foundation for increasing the mass production of railway clips of this size. [ABSTRACT FROM AUTHOR]

[Display omitted] • A device for testing anti-melting loss performance of coating was designed. • Anti-melting loss performance of Ni60A coating was studied for the first time. • A proposal to improve the anti-melting loss performance was put forward. Coppery tuyere is a core component in iron-making blast furnace, mainly used for supplying hot air and injecting pulverized coal. Due to the harsh service environment, tuyeres are prone to failure by wear and melting loss. Surface coatings can significantly improve the wear resistance of copper surface, but their anti-melting loss performance is still a research blank. This paper designed a novel device for testing the anti-melting loss performance of coatings. The device included plasma melting-drop, induction preheating and infrared temperature control systems, which can simulate the process of coating being corroded by molten iron under service conditions. Anti-melting loss test results of Ni60A coating indicated that the molten iron and the γ-(Cu, Fe, Ni) solid solution in the coating can form metallurgical bonding by element diffusion, thus adhering on the coating surface. The continuous accumulation of iron will worsen the heat-transfer capability of tuyere, making it more likely to cause melting loss. Adding ceramics in the Ni60A alloy or developing coating materials with higher melting points are expected to improve the anti-melting loss performance of coatings on coppery tuyere. [ABSTRACT FROM AUTHOR]

The films of (MoTaWNb) 1- x Y x high entropy amorphous alloy were successfully deposited by direct current magnetron sputtering under different contents of Y additions. The microstructure, mechanical properties, and friction behaviors of the as-deposited (MoTaWNb) 1- x Y x films were investigated. The results show that the films were mainly composed of amorphous and body-centered cubic (BCC) phases, and the proportion of the amorphous phase increases gradually with the increase in Y content. When the deposited film has a typical amorphous phase with a uniform and dense fibrous-shaped columnar microstructure, it shows a maximum nano-hardness of 6.74 GPa. However, the growth of V-shaped columnar microstructures during film deposition increases its surface roughness and decreases its mechanical properties. Abrasion wear, oxidation wear, and delamination wear dominate the wear process, and the evolution of the frictional behaviors of deposited films is directly related to their structural and mechanical changes. The wear resistance of (MoTaWNb) 1- x Y x films with wear rates of the order of 10−5 mm3·N−1·m−1 is achieved by tuning the Y additions, and this film can be used as a potential candidate for wear-resistant coatings. • The (MoTaWNb)1-xYx refractory high entropy alloy films are deposited by magnetron sputtering. • The films exhibit a mixed microstructure of BCC and amorphous phases. • The growth mechanism of the (MoTaWNb)1-xYx films is affected by Y addition with varying internal stress and atomic diffusion. • The wear mechanisms of the films can be attributed to a combination of abrasion, delamination, and oxidation wear. [ABSTRACT FROM AUTHOR]

In general, different extrusion conditions will affect the microstructure of magnesium alloys and further determine the mechanical properties. The effects of extrusion parameters and heat treatment processes such as extrusion speed, pre-forging, annealing time, extrusion ratio and cooling rate on the microstructure, texture evolution and tensile properties of Mg-2Gd-0.3Zr alloys were investigated in this study. Compared with the as-cast alloy, the extrusion process significantly refines the grains and exhibit the rare earth texture. With the increase of extrusion speed and annealing time, the growth of recrystallized grains is accelerated, leading to the increase of elongation. Large pre-forging deformation achieves to refine the grains by promoting recrystallization nucleation, resulting in increased strength of Mg-2Gd-0.3Zr alloy. Decreasing the extrusion ratio or increasing the cooling rate will introduce coarse un-DRXed grains, which transformed the texture into the basal texture. In particular, the effect of rapid cooling on refining the recrystallized grains is also obvious. Different extrusion conditions influence the mechanical properties of the Mg-2Gd-0.3Zr alloy through the grain size, proportion of non-recrystallization region and texture type. [ABSTRACT FROM AUTHOR]

A multi-level and multi-site local mesh refinement method is developed to calculate the local responses of 2D problems with multi-site microstructures. The optimal mesh density is employed for all subregions to reduce the computational cost and meshing difficulty, and overcome the obstacle resulted from the mesh conformity requirement. The two-level, three-level, and multi-level mesh refinement methods are developed firstly; the refined meshes in the critical regions are regarded as a super element. And then, based on two-level and three-level methods, a multi-level and multi-site refinement method is established. [ABSTRACT FROM AUTHOR]

Microstructure evolution of the joints formed by Ag-6.6 mol% Cu brazing BaCo0.7Fe0.2Nb0.1O3-δ (BCFN) ceramic after long-term heat treatment in different atmospheres was revealed. After heat treatment in air, the layered structure in the original interfacial reaction layer disappears, accompanied by the aggregation and growth of the interfacial products. The thickness of the reaction layer increased first and then stabilized. Under the action of the concentration gradient, the residual copper oxide diffused along the pores of BCFN matrix and continued to react with the matrix until it exhausted. The types of interfacial products remained unchanged, which were Ba2Cu2O5 and Co-Cu-O (solid solution). However, serious decomposition of interfacial products (Ba2Cu2O5) occurred due to the low oxygen partial pressure after heat treatment in argon, resulting in the formation of holes and cracks. Part of cobalt precipitated from the BCFN matrix and formed a cobalt-rich phase at the junction of Ag-Cu alloy and interfacial reaction zone. Results showed that the joint microstructure is unstable at high temperature. Controlling the amount of the interfacial products formed during brazing is key to improving the stability of the joint, which provides a theoretical support for further optimizing the sealing quality of membrane components. [ABSTRACT FROM AUTHOR]

Through carbon and manganese partitioning to austenite from polygonal ferrite, bainite and martensite, retained austenite (RA) could be stabilized at room temperature in advanced high-strength steels. Alternatively, the present study utilized lamellar pearlite as an initial microstructure for austenite reversion treatment at 750 °C and successfully produced the microstructure consisting of film RA and lath martensite. This heat treatment is named as pearlitic reversed austenitization. The austenite formed from cementite was enriched in manganese and, in turn, was retained at room temperature; whereas, the austenite formed from ferrite was depleted in manganese and, in turn, transformed to martensite during cooling to room temperature. Different holding times at 750 °C led to different microstructures and RA fractions. After tempering 1 min at 300 °C, a high ultimate tensile strength of 1791 MPa and a decent total elongation of 8.1% were achieved due to tempered martensite matrix and transformation-induced plasticity effect. These tensile properties are comparable to C250 maraging steel. This investigation opens a new avenue to produce high-strength and good ductility steels based on pearlite. [ABSTRACT FROM AUTHOR]

Cu-coated graphite was applied to modify the interface of Cu-Ni-graphite composite used as switch slide baseplate. Up to now, interfacial characterization and modification mechanisms of Cu modified Cu-Ni-graphite composite are seldom researched. In this study, Cu-coated graphite was deposited by chemical plating, and Cu modified Cu-Ni-graphite composite was prepared by powder metallurgy. Both the microstructure characterizations of Cu-coated graphite and interfacial morphologies of the composite were investigated. Then, the comparison of mechanical properties of unmodified and Cu modified Cu-Ni-graphite composite was discussed. The results showed that the Cu coating was made of fine particles with uniform distribution and with the average thickness of 1.05 μm. The mutual diffusion was about 2.54 μm width at the interface. The interfacial modification mechanism of Cu coating in the composite was that the decreasing of diffusion activity both in the graphite and matrix; and the increase of diffusion driving force at the interface. The interfacial bonding method in the transition from mechanical bonding to the combination of mechanical bonding and diffusion bonding. Compared with the unmodified composite, the flexural strength raised 24.4%, and hardness increased by 9%. [ABSTRACT FROM AUTHOR]

The electromigration microstructure and properties of Ni-rGO reinforced Sn2. 5Ag0.7Cu0. 1RE composite solder/Cu soldering joint was investigated by scanning electron microscope, the energy dispersive spectrometer,the X-ray diffraction and micro-shear test. The results show that the thickness of intermetallic compound( IMC) Cu6Sn5 and Cu3Sn in Sn2. 5Ag0. 7Cu0. 1RE composite solder/Cu soldering joint increases with current stressing time at the anode by a current density of 1 X 104 A/cm² at 120 T . The thickness of Cu6Sn5 decreases and Cu3Sn increases first and then decreases at the cathode. The addition of Ni-rGO significantly inhibits the growth of Cu6Sn5 and the formation of micro-voids in the Ni-rGO reinforced Sn2. 5Ag0. 7Cu0. 1RE composite solder/Cu soldering joint at the cathode by electromigration and increase the shear strength of the soldering joint. The shear strength of Ni-rGO reinforced Sn2. 5Ag0. 7Cu0. 1RE composite solder/Cu soldering joint is 47. 8% higher than that of the soldering joint without Ni-rGO after current stressing for 72 h. The shear fracture of composite solder/Cu soldering joint changes from ductile fracture dominated by dimples at the cathode soldering zone to mixed fracture composed of cleavage, quasi-cleavage and a few dimples in the IMC interface. [ABSTRACT FROM AUTHOR]