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In this paper, the precipitation behavior and its effect on resistivity in a new type of nickel–iron-based alloy during short-term aging were investigated. During the aging process, the γ ′ phase increases in average size and decreases in number, with its area fraction fluctuating over time. This fluctuation is caused by the mismatch in the redissolution and growth rates of the γ ′ phase. As the area fraction of the γ ′ phase increases, the content of solute atoms in the matrix that scatter electrons decreases, lowering the resistivity of the alloy. Additionally, the continuous precipitation of M 23 C 6 at grain boundaries during aging causes the resistivity to gradually increase. This paper explains the fluctuation in the total amount of γ ′ phase during short-term aging and proposes a new method for characterizing the precipitation behavior of the γ ′ phase in the novel alloy using the relative trend of resistivity changes. [ABSTRACT FROM AUTHOR]

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In this paper, TiN-Ni nanostructured composite films with different Ni contents are prepared using the magnetron sputtering method. The composition, microstructure, and mechanical properties of composite films are analyzed using an X-ray energy spectrometer (EDS), a scanning electron microscope (SEM), X-ray diffraction technology (XRD), a transmission electron microscope (TEM), and nanoindentation. All the films grow in a columnar crystal structure. There are only TiN diffraction peaks in the XRD spectrum, and no diffraction peaks of Ni and its compounds are observed. The addition of the Ni element disrupts the integrity of TiN lattice growth, resulting in a decrease in the grain size from 60 nm in TiN to 25 nm at 20.6% Ni. The film with a Ni content of 12.4 at.% forms a nanocomposite structure in which the nanocrystalline TiN phase (nc-TiN) is surrounded by the amorphous Ni (a-Ni) phase. The formation of nc-TiN/a-Ni nanocomposite structures relies on the good wettability of Ni on TiN ceramics. The hardness and elastic modulus of the film gradually decrease with the increase in Ni content, but the toughness is improved. The hardness and elastic modulus decrease from 19.9 GPa and 239.5 GPa for TiN film to 15.4 GPa and 223 GPa at 20.6 at.% Ni film, respectively, while the fracture toughness increases from 1.5 MPa·m1/2 to 2.0 MPa·m1/2. The soft and ductile Ni phase enriched at the TiN grain boundaries hinders the propagation of cracks in the TiN phase, resulting in a significant increase in the film's toughness. The research results of this paper provide support for the design of TiN-Ni films with high strength and toughness and the understanding of the formation mechanism of nanocomposite structures. [ABSTRACT FROM AUTHOR]

P92 steel is a modern martensitic heat-resistant steel currently used for seamless products for pressure equipment operating in supercritical operating parameters. The paper presents the results of a study on the strength properties and structure of a P92 steel welded joint used for pressure components of power units. The paper presents an assessment of the suitability for further operation of both the parent material and a circumferential similar welded joint of finished products in the form of P92 steel pipes after annealing for 3000 hours at 600 and 650°C. Annealing at 650°C results in faster increase in the size of the precipitates and their coagulation along grain boundaries of former austenite and martensite laths. The changes in mechanical properties were compared in relation to the state of the structure of the parent material and the material of the welded joint. Quantitative analysis of M23C6 precipitates was also carried out. [ABSTRACT FROM AUTHOR]

In this paper, the influence of Cr element on the mechanical properties of welded joints of gas-shielded solid wire used in oil and gas long-distance pipelines was studied by means of tensile test, impact test, and hardness test, and the microstructure and crack propagation path of weld were characterized by means of an optical microscope, scanning electron microscope, and electron backscattering diffraction. The results show that with the addition of Cr, the strength and toughness of the weld are significantly improved, in which the tensile strength is increased from 607 MPa to 656 MPa, and the impact toughness is increased from 126.37 J to 223.79 J. The proportion of the ferrite side plate in the weld structure is reduced by about 20%, and the effective grain size of acicular ferrite is reduced by about 15%. The reason is that the addition of the Cr element improves the hardenability of the weld structure, inhibits the formation of the ferrite side plate, and promotes the effective refinement of acicular ferrite, which increases the proportion of high-angle grain boundaries in the weld, effectively hindering the crack propagation, improves the crack propagation work, and thus improves the strength and toughness of the weld. [ABSTRACT FROM AUTHOR]

This paper employed squeeze-casting (SC) technology to develop a novel Al-7Si-1.5Cu-1.2Ni-0.4Mg-0.3Mn-0.15Ti heat-resistant alloy, addressing the issue of low room/high temperature elongation in traditional gravity casting (GC). Initially, the effects of SC and GC processes on the microstructure and properties of the alloy were investigated, followed by an examination of the evolution of the microstructure and properties of the SC samples over thermal exposure time. The results indicate that the SC process significantly improves the alloy's microstructure. Compared to the GC alloy, the secondary dendrite arm spacing of the as-cast SC alloy is refined from 50.5 μm to 18.5 μm. Meanwhile, the size and roundness of the eutectic Si phase in the T6-treated SC alloy are optimized from 11.7 μm and 0.75 μm to 9.5 μm and 0.85 μm, respectively, and casting defects such as porosity are reduced. Consequently, the ultimate tensile strengths (UTSs) at room temperature and at 250 °C of the SC alloy are 5% and 4.9% higher than that of GC alloy, respectively, and its elongation at both temperatures shows significant improvement. After thermal exposure at 250 °C for 120 h, the morphology of the residual second phase at the grain boundaries in the SC alloy becomes more rounded, but the eutectic Si and nano-precipitates undergo significant coarsening, resulting in a 49% decrease in UTS. [ABSTRACT FROM AUTHOR]

High-temperature oxidation resistance is the major influence on the high-temperature service stability of refractory high entropy alloys. The oxidation behavior of lightweight Al0.2CrNbTiV refractory high entropy alloy coatings with different dilution ratios at 650 °C and 800 °C deposited by high-speed laser cladding was analyzed in this paper. The oxidation kinetic was analyzed, the oxidation resistance mechanism of the Al0.2CrNbTiV coating was clarified with the analysis of the formation and evolution of the oxidation layer, and the effect of the dilution rate on high-temperature performances was revealed. The results showed that the oxide layer was mainly composed of rutile oxides (Ti, Cr, Nb)O2 after isothermal oxidation at 650 °C and 800 °C for 50 h. The Al0.2CrNbTiV coating in low dilution exhibited better oxidation performance at 650 °C, due to the dense oxide layer formed with the synergistic growth of fine AlVO3 particles and (Ti, Cr, Nb)O2, and higher percentage of Cr, Nb in (Ti, Cr, Nb)O2 strengthened the lattice distortion effect to inhibit the penetration of oxygen. The oxide layer formed at 800 °C for the Al0.2CrNbTiV coating was relatively loose, but the oxidation performance of the coating in high dilution improved due to the precipitation of Cr2Nb-type Laves phases along grain boundaries, which inhibits the diffusion of oxygen. [ABSTRACT FROM AUTHOR]

As a soft magnetic material with excellent performance, silicon steel is widely used in motors and transformers, but its mechanical properties drop sharply when the silicon content is too high. Therefore, it is of great significance to study its influence on mechanisms to improve the product quality of silicon steel. In this paper, Fe-6.5 wt%Si silicon steel was prepared by vacuum tube furnace, combined with a metallographic experiment, and scanning electron microscope analysis to explore the influence of silicon infiltration temperature and time on grain and grain boundary size, and the tensile test of silicon infiltration 120 s at 1200 °C was obtained by the tensile test's extension parameter. Given the difficulty in adjusting the size and structure of grains and grain boundaries in the test, this paper discusses the influence of different microstructures on the mechanical properties of silicon steel through tensile simulation. The tensile results show that grain refinement helps to improve the strength and elongation of silicon steel, and columnar grains can slightly increase their strength but greatly reduce the strain rate of silicon steel. This method can greatly reduce the research and development time of Fe-6.5 wt%Si silicon steel and can be used to improve the comprehensive performance of silicon steel. [ABSTRACT FROM AUTHOR]

Grain size has a significant effect on the mechanical properties of metals. It is very important to accurately rate the grain size number of steels. This paper presents a model for automatic detection and quantitative analysis of the grain size of ferrite–pearlite two-phase microstructure to segment ferrite grain boundaries. In view of the challenging problem of hidden grain boundaries in pearlite microstructure, the number of hidden grain boundaries is inferred by detecting them with the confidence of average grain size. The grain size number is then rated using the three-circle intercept procedure. The results show that grain boundaries can be accurately segmented by using this procedure. According to the rating results of grain size number of four types of ferrite–pearlite two-phase microstructure samples, the accuracy of this procedure is greater than 90%. The grain size rating results deviate from those calculated by experts using the manual intercept procedure by less than Grade 0.5—the allowable detection error specified in the standard. In addition, the detection time is shortened from 30 min of the manual intercept procedure to 2 s. The procedure presented in this paper allows automatic rating of grain size number of ferrite–pearlite microstructure, thereby effectively improving the detection efficiency and reducing the labor intensity. [ABSTRACT FROM AUTHOR]

Currently, new functional materials are being created with a strong emphasis on their ecological aspect. Materials and devices based on DNA biopolymers, being environmentally friendly, are therefore very interesting from the point of view of applications. In this paper, we present the results of research on complexes in the powder form based on plasmid DNA (pDNA) and three surfactants with aliphatic chains containing 16 carbon atoms (cetyltrimethylammonium chloride, benzyldimethylhexadecylammonium chloride and hexadecylpyridinium chloride). The X-ray diffraction results indicate a local hexagonal packing of DNA helices in plasmid DNA complexes, resembling the packing for corresponding complexes based on linear DNA. Based on the Fourier-transform infrared spectroscopy results, the DNA conformation in all three complexes was determined as predominantly of A-type. The two relaxation processes revealed by dielectric spectroscopy for all the studied complexes are connected with two different contributions to total conductivity (crystallite part and grain boundaries). The crystallite part (grain interior) was interpreted as an oscillation of the polar surfactant head groups and is dependent on the conformation of the surfactant chain. The influence of the DNA type on the properties of the complexes is discussed, taking into account our previous results for complexes based on linear DNA. We showed that the type of DNA has an impact on the properties of the complexes, which has not been demonstrated so far. It was also found that the layer of pDNA–surfactant complexes can be used as a layer with variable specific electric conductivity by selecting the frequency, which is interesting from an application point of view. [ABSTRACT FROM AUTHOR]

In this paper, quantitative two-dimensional (2-D) phase-field simulations were performed to gain insight into the effects of B and Nb for Al-Ti-Nb balanced-ratio GH4742 alloys. The microstructure evolution during the precipitation process was simulated using the MICRESS (MICRostructure Evolution Simulation Software) package developed in the formalism of the multi-phase field model. The coupling to CALPHAD (CALculation of PHAse Diagram) thermodynamic databases was realized via the TQ interface. The morphological evolution, concentration distribution, and thermodynamic properties were extensively analyzed. It is indicated that a higher Nb content contributes to a faster precipitation rate and higher amounts and the smaller precipitate size of the γ′ phase, contributing to better mechanical properties. The segregation of the W element in γ′ precipitate due to its sluggish diffusion effect has also been observed. Higher temperatures and lower B contents accelerate the dissolution of boride and reduce the precipitation of borides. With the increased addition of B, the formation of borides may have a pinning effect on the grain boundary to hinder the kinetic process. In addition, borides are prone to precipitate around the interface rather than in the bulk phase. Once the M3B2 borides nucleate, they grow in the consumption of γ′ phases. [ABSTRACT FROM AUTHOR]

This paper constituted an extension of two previous studies concerning the mathematical development of the grain boundary grooving in polycrystalline thin films in the cases of evaporation/condensation and diffusion taken separately. The thermal grooving processes are deeply controlled by the various mass transfer mechanisms of evaporation–condensation, surface diffusion, lattice diffusion, and grain boundary diffusion. This study proposed a new original analytical solution to the mathematical problem governing the grain groove profile in the case of simultaneous effects of evaporation–condensation and diffusion in polycrystalline thin films by resolving the corresponding fourth-order partial differential equation ∂ y ∂ t = C ∂ 2 y ∂ x 2 − B ∂ 4 y ∂ x 4 obtained from the approximation ∂ y ∂ x 2 ≪ 1 . The comparison of the new solution to that of diffusion alone proved an important effect of the coupling of evaporation and diffusion on the geometric characteristics of the groove profile. A second analytical solution based on the series development was also proposed. It was proved that changes in the boundary conditions of the grain grooving profile largely affected the different geometric characteristics of the groove profile. [ABSTRACT FROM AUTHOR]

Magnetoresistance, the change in resistance with applied magnetic fields, is crucial to the magnetic sensor technology. Linear magnetoresistance has been intensively studied in semimetals and semiconductors. However, the air-stable oxides with a large linear magnetoresistance are highly desirable but remain to be fully explored. In this paper, we report the direct observation of linear magnetoresistance in polycrystalline MoO2 without any sign of saturation up to 7 T under 50 K. Interestingly, the linear magnetoresistance reaches as large as 1500% under 7 T at 2 K. The linear field dependence is in great contrast to the parabolic behavior observed in single-crystal MoO2, probably due to phonon scattering near the grain boundaries. Our results pave the way to comprehending magneto-transport behavior in oxides and their potential applications in magnetic sensors. [ABSTRACT FROM AUTHOR]

In this paper, the influence of bismuth content and heating rate on the morphology of MnS inclusions in bismuth-containing free-cutting steel during heating was investigated through in situ observation experiments and 3D electrolytic corrosion experiments. By observing the microscopic morphology of inclusions in the original sample, it was found that MnS inclusions in the sample were rod-shaped, spherical, irregular, small in size, and mostly clustered at the grain boundary in the form of chains and divergences. With the addition of bismuth, MnS inclusions of a larger size appear in the steel, and the inclusions distributed at grain boundaries are also reduced. When bismuth (0.010~0.020%) is added to the steel, MnS is mainly spherical and uniformly dispersed in the steel matrix. If the bismuth content is too high, the inclusions aggregate. Through in situ observations of the inclusions in the sample, it was found that the addition of bismuth in the heating process delays the appearance of ferrite grain boundaries and contributes to the spheroidization of MnS inclusions. Mn and S elements can fully diffuse slowly in the matrix with a heating rate below 1 °C/s and a long holding time (300 s), which provides the possibility for the spheroidization of MnS inclusions. [ABSTRACT FROM AUTHOR]

As the demand for lithium-ion batteries increases, higher quality requirements are being placed on pure aluminum ultra-thin strips, one of the main materials used in lithium-ion battery current collectors. Roller vibration during the rolling process of pure aluminum ultra-thin strips is unavoidable and significantly affects the quality of the strips. This paper uses 1A99 pure aluminum ultra-thin strips as raw materials and employs a controlled vibration method during the rolling process to obtain products under two conditions: stable rolling and vibrational rolling. The surface and cross-section of the aluminum strips were characterized using scanning electron microscopy (SEM), and the microstructure of the surface and cross-section was studied using electron backscatter diffraction (EBSD) technology. The results show that, during stable rolling, the surface quality of the aluminum strip is good without defects. Under vibration, obvious vibration marks appear on the surface of the aluminum strip, showing characteristics of peaks and troughs. With the increase in strain at the trough position, there is a transition from low-angle grain boundaries to high-angle grain boundaries, and the grain size is uneven at the peak and trough positions, with noticeable grain refinement at the troughs. At the same time, under the influence of vibration, the aluminum strip induces a different texture morphology from conventional rolling. Due to the different plastic strains at the peak and trough positions, a texture alternation phenomenon occurs at these positions. The tensile test results indicate that aluminum strips exhibit poor mechanical properties under roller vibration, with the reduction in mechanical performance primarily attributed to the uneven microstructure distribution caused by roller vibration. [ABSTRACT FROM AUTHOR]

This paper investigates the microscale engineering aspects of n-type doped GaSb to address the challenges associated with achieving high electrical conductivity and precise dopant distribution in this semiconductor material. AC impedance spectroscopy is employed as a reliable technique to characterize the microstructural and electrical properties of GaSb, providing valuable insights into the impact of grain boundaries on overall electrical performance. The uneven distribution of dopants, caused by diffusion, and the incomplete activation of introduced dopants pose significant obstacles in achieving consistent material properties. To overcome these challenges, a careful selection of alloying elements, such as bismuth, is explored to suppress the formation of native acceptor defects and modulate band structures, thereby influencing the doping and compensator formation processes. Additionally, the paper examines the effect of microwave annealing as a potential solution for enhancing dopant activation, minimizing diffusion, and reducing precipitate formation. Microwave annealing shows promise due to its rapid heating and shorter processing times, making it a viable alternative to traditional annealing methods. The study underscores the need for a stable grain boundary passivation strategy to achieve significant improvements in GaSb material performance. Simple grain size reduction strategies alone do not result in better thermoelectric performance, for example, and increasing the grain boundary area per unit volume exacerbates the issue of free carrier compensation. These findings highlight the complexity of achieving optimal doping in GaSb materials and the importance of innovative analytical techniques and controlled doping processes. The comprehensive exploration of n-type doped GaSb presented in this research provides valuable insights for future advancements in the synthesis and optimization of high-conductivity nanostructured n-type GaSb, with potential applications in thermoelectric devices and other electronic systems. [ABSTRACT FROM AUTHOR]

A metal passivator is often added to transformer oil to inhibit oil sulfur corrosion. However, the addition of passivator can result in gaseous anomaly in the oil and need to be added regularly. In this paper, the copper winding of transformer is treated by grain boundary engineering technology, and the corrosion resistance of the winding before and after treatment is compared according to IEC 62535 standard. The experimental results show that the copper windings treated by grain boundary engineering technology have good corrosion resistance. The original copper winding began to corrode when dibenzyl disulphide (DBDS) concentration achieved 50 mg/kg. Even DBDS concentration was up to 2000 mg/kg, the treated windings still had a good anticorrosion effect. Further, corrosion resistance mechanisms were explored, it is found that the corrosion resistance of the treated winding is better than that of addition passivator. The statistical analysis of the internal grain boundary of the copper windings shows that the twin grain boundary of treated windings increases obviously, and the increased twin grain boundary breaks the connectivity of the grain boundary, thus improving the corrosion resistance of the windings. [ABSTRACT FROM AUTHOR]

This paper investigates the temperature dependence of random telegraph noise (RTN) in 3-D NAND Flash technologies. Experimental results on memory arrays reveal an increase of RTN when temperature is reduced, which is mainly attributed to the growth of the amplitude of the fluctuations arising from RTN traps. A direct proof of this growth is provided by directly monitoring some RTN waveforms arising from single traps in cells out of either memory arrays or test elements. In order to explain this evidence, the TCAD model for polysilicon NAND strings presented in Part I of this paper is adopted and extended to address the amplitude of the threshold-voltage shift coming from the trapping of a single electron at different positions in cell channel. Numerical results successfully reproduce the experimental trends with temperature and allow to explain them in terms of stronger nonuniformities in polysilicon inversion when temperature decreases. In particular, the reduction of temperature makes the string currentmore controlledby the polysilicon grain boundaries, increasing, in turn, the amplitude of the RTN fluctuations arising from traps placed on or close to them. [ABSTRACT FROM AUTHOR]

Aero-engines can be exposed to One Engine Inoperative (OEI) conditions during service, and the resulting overheating effect may significantly impact their structural integrity and flight safety. This paper focuses on the influence of overheating on the microstructural evolution and tensile properties of the GH4720Li alloy, a nickel-based polycrystalline superalloy commonly used in turbine disks. Based on the typical OEI operating conditions of a real aero-engine, a series of non-isothermal high-temperature tensile tests involving an OEI stage of 800 °C were conducted. The effects of OEI-induced overheating on the microstructure and tensile properties of the GH4720Li alloy were investigated. The results showed that, after OEI treatment, the primary γ′ phase in this alloy was partially dissolved. The GH4720Li superalloy also exhibited numerous microcracks at the grain boundaries, resulting in complex effects on its tensile properties. The alloy's yield strength and ultimate tensile strength were slightly decreased, whereas its ductility decreased considerably. The OEI-induced embrittlement phenomenon was mainly caused by the non-uniform distribution of the tertiary γ′ phase within grains. The formation of microcracks nucleated at the interfaces between the primary γ′ precipitates and γ matrix phase was another key factor. [ABSTRACT FROM AUTHOR]

This paper examines the corrosion behavior of the welding heat-affected zone (HAZ) of HDR (high chromium, duplex, corrosion-resistant) duplex stainless steel, which currently faces corrosion-related challenges in marine seawater systems. The corrosion behavior of the HAZ was studied using microstructure analysis, polarization curve experiments, and double-loop potentiodynamic reactivation experiments. The results show that (1) the covering welding current can promote the formation of austenite in the HAZ, and that the covering welding current has no strict correspondence with the formation of austenite; (2) increasing the welding gap properly can facilitate the formation of austenite; (3) increasing the covering welding current enhances the material's pitting resistance, and a covering welding current of 70 A, coupled with a covering welding current of 100 A, represents a reasonable choice in terms of achieving a stronger pitting resistance; (4) in terms of intergranular corrosion resistance, increasing the covering welding current is not conducive to the intergranular corrosion resistance of the material, as the covering current will promote the precipitation of the secondary phase at the grain boundary, thus reducing its intergranular corrosion resistance; and (5) reducing the welding current appropriately contributes to improving the stability of the grain boundary. [ABSTRACT FROM AUTHOR]

G115 steel is a novel martensitic heat-resistant steel, primarily utilized in the main steam pipelines and collectors of ultra-supercritical thermal power units. However, the oxidation resistance of martensitic steels in the high-temperature steam environment is usually suboptimal, significantly affecting the efficiency of power plants. In this paper, shot peening (SP) is employed as a surface treatment method for G115 steel, and the oxidation kinetics, oxide layer thickness, and microstructure of shot-peened G115 samples are compared with those of G115 steel. The results indicate that in the 650 °C steam environment, the oxidation kinetics of the shot-peened samples follow the parabolic law and that the oxidation weight gain is significantly smaller than that of the non-shot-peened samples. The higher the SP intensity, the smaller the oxidation weight gain and the better the oxidation resistance. This can be attributed to the fragmentation of the grains in the surface layer caused by external stress during SP, which creates a multitude of grain boundaries that can provide rapid diffusion pathways for corrosion-resistant Cr atoms, resulting in the accelerated outward diffusion of Cr atoms from the substrate. Simultaneously, a continuous and dense FeCr2O4 protective layer is produced at the interface between the SP layer and the substrate, obstructing the inward diffusion of oxygen and enhancing the oxidation resistance of G115 steel. [ABSTRACT FROM AUTHOR]

In this paper, three types of dental alloys often used in practice were investigated, namely: NiCrMoSiVCuFe, NiCrMoSiFeAlMgZn and CuAlNiFeMgZnSi to evaluate the chemical homogeneity. Energy Dispersive X-ray Spectroscopy (EDS) and Backscattered-Electron (BSE) Imaging were used to obtain valid results on the structure and distribution of constituent elements in the investigated alloys. All samples were investigated in 3 different (micron) areas, respectively: a central area and two marginal areas. The EDS investigations followed the identification of the spectral lines, respectively the irrefutable highlighting of the composition of the sample and, subsequently, the distributions of the identified elements in the specified areas to be compared. The mapping distributions of the elements can reveal local homogeneity/heterogeneity (in bottle heterogeneity) and homogeneity at the sample (implant) level (between bottles heterogeneity). The microstructural inhomogeneity resulting from the formation of compounds in the grain boundaries is primary and determines, therefore, elemental or chemical heterogeneity. [ABSTRACT FROM AUTHOR]

In this paper, a one-step hot extrusion dual-stage solution treatment method is employed to fabricate high-strength and tough T-shaped complex cross-section 7055 (Al-Zn-Mg-Cu-Zr) alloy profiles, and a detailed investigation is conducted on the microstructure and mechanical properties. The results indicate that the comprehensive mechanical properties of the 7055 aluminum extruded alloy using the two-stage solution aging treatment are excellent. This is particularly evident in the balance between strength and ductility, where outstanding strength is accompanied by a plasticity that is maintained at 13.2%. During the extrusion process, the deformation textures are mainly composed of brass and copper, forming a 15.1% recrystallization texture Cube. In addition, the equilibrium phase η(MgZn2) precipitated in the grain is the main strengthening phase, and there are large discontinuous grain boundary precipitates at the grain boundary, which hinders the grain boundary dislocation movement and has great influence on the mechanical properties of alloy materials. [ABSTRACT FROM AUTHOR]

Retrogression and re-aging (RRA) treatment has been proven to effectively overcome the trade-off between strength and corrosion resistance. Current research focuses on the heating rate, temperature, and holding time of retrogression treatment while ignoring the retrogression cooling ways. In this paper, the effects of RRA treatment with different retrogression cooling ways on the microstructure and properties of newly developed T'/η' strengthened Al-Zn-Mg-Cu alloys were investigated by performing tests on mechanical properties, intergranular corrosion (IGC) resistance, and electrochemical corrosion behavior. The results show that the mechanical properties of samples subject to RRA treatment with water-quenching retrogression (ultimate tensile strength, yield strength, and elongation of 419.2 MPa, 370.2 MPa, and 15.9, respectively) are better than those of air-cooled and furnace-cooled samples. The corrosion resistance of water-quenching (IGC depth of 162.2 μm, corrosion current density of 0.833 × 10−5 A/cm2) and furnace-cooled samples (IGC depth of 123.7 μm, corrosion current density of 0.712 × 10−5 A/cm2) is better than that of air-cooled samples. Microstructure characterization reveals that the effect of the retrogression cooling rate on mechanical properties is related to the size of T'/η' precipitates with grains as well as the proportion of T' and η', while the difference in corrosion resistance depends on the continuity of grain boundary precipitates (GBPs). With mechanical properties, corrosion resistance, and time cost taken into consideration, it is appropriate to select water quenching for retrogression. These findings offer valuable insights for further design to achieve superior performance in various applications. [ABSTRACT FROM AUTHOR]

In this paper, the microstructure of Ti-6Al-4V alloy sintered by spark plasma was studied by multi-pass of hot compression experiment, and the influence of different thermal deformation parameters (hot compression temperature deformation: 950°C–20% for one pass, 850°C–20% for two passes and 900°C–10%/20%/30% for three passes) was studied. The results show that the dynamic recrystallization characteristic behavior appears in the three deformation passes. The microstructure after the first and second pass deformation is mainly composed of Widmanstätten structure. With the increase of strain rate, the thickness of lamellar α decreases gradually. In three pass, the grain boundary α phase and the layered α phase are twisted and bent when the deformation amount is 10% and 20%, and the deformation amount increases to 30%. The spheroidization of lamellar α phase occurs, and the size of β grain decreases obviously. The content of equiaxed α phase and grain size decrease with the increase of strain rate. [ABSTRACT FROM AUTHOR]

The paper deals with the effect of the morphology characteristics, grain size, and the volume fraction of AlN- and NbC-precipitated particles on the prior austenite grain growth behavior in the Al- and Nb-microalloying 20MnCr gear steel during pseudo-carburizing heat treatments. The results indicate that the Nb addition in 20MnCr gear steel have a better effect on preventing austenite grain growth. The coarsening time after pseudo-carburizing in the Nb-microalloyed 20MnCr steel are improved by about 4 h compared with the Al-microalloyed steel. The precipitated particles coarsen and the number decreases with the pseudo-carburization temperature increasing, resulting in a reduction in the pinning pressure of the precipitated particles on the austenite grain boundaries. When the pseudo-carburization temperature reaches 1150 °C, the precipitated particles no longer have the ability to pin the austenite grain boundaries. In addition, the kinetics model for austenite grain growth under the process of the pinning and coarsening of the precipitated particles was established. [ABSTRACT FROM AUTHOR]

In the present paper, microstructural changes in two alloys, IN617 and DMV617 mod, after 5 h and 1000 h of aging at 700 °C were investigated using scanning transmission electron microscopy. The mechanical properties of the samples were evaluated using hardness tests. Precipitates were identified using energy-dispersive X-ray spectroscopy analysis. After long-term aging, intensive precipitation of the M23C6 carbides and γ′ intermetallic phase in the microstructure of alloys was observed. In the IN617 alloy, continuous layers of M23C6 carbides along the grain boundaries after long-term aging were observed. The minor addition of boron to the DMV617 mod alloy is advantageous in microstructure formation during long-term aging because it decreases the agglomeration of M23C6 at the grain boundaries. [ABSTRACT FROM AUTHOR]

The primary objective of this paper is to investigate the influence of deformation degree on the microstructure and properties of a Ni-based superalloy. An upsetting experiment was conducted using a free-forging hammer to achieve a deformation degree ranging from 60% to 80%. The impact of the forging deformation degree on the hardness and high-temperature erosion performance was evaluated using the Rockwell hardness tester (HRC) and high-temperature erosion tester, respectively. The experimental results indicate that as the deformation degree increased, the hardness of the forged material progressively increased while the rate of high-temperature erosion gradually decreased. In order to comprehensively study the mechanism behind the variations in forging performance, optical microscopy (OM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM) were employed. The findings reveal that as the deformation degree increased, the presence of small-angle grain boundaries and an increase in grain boundary area contributed to enhanced hardness in the alloy forgings. Furthermore, it was discovered that grain boundaries with twin orientation promoted dynamic recrystallization during deformation, specifically through a discontinuous dynamic recrystallization mechanism. Additionally, the precipitated γ′ phase in the alloy exhibited particle sizes ranging from 40 to 100 nm. This particle size range resulted in a higher critical shear stress value and a more pronounced strengthening effect on the alloy. [ABSTRACT FROM AUTHOR]

The microstructure of polycrystals is known to govern the performance of structural materials. This drives the need for mechanical characterization methods capable of probing large representative volumes at the grain and subgrain scales. In this paper, the use of in situ diffraction contrast tomography (DCT) along with far-field 3D X-ray diffraction (ff-3DXRD) at the Psiche' beamline of Soleil is presented and applied to study crystal plasticity in commercially pure titanium. A tensile stress rig was modified to comply with the DCT acquisition geometry and used for in situ testing. DCT and ff-3DXRD measurements were carried out during a tensile test of a tomographic Ti specimen up to 1.1% strain. The evolution of the microstructure was analyzed in a central region of interest comprising about 2000 grains. Using the 6DTV algorithm, DCT reconstructions were successfully obtained and allowed the characterization of the evolution of lattice rotation in the entire microstructure. The results are backed up by comparisons with EBSD and DCT maps acquired at ESRF-ID11 that allowed the validation of the orientation field measurements in the bulk. Difficulties at the grain boundaries are highlighted and discussed in line with increasing plastic strain during the tensile test. Finally, a new outlook is provided on the potential of ff-3DXRD to enrich the present dataset with access to average lattice elastic strain data per grain, on the possibility of performing crystal plasticity simulations from DCT reconstructions, and ultimately on comparisons between experiments and simulations at the scale of the grain. [ABSTRACT FROM AUTHOR]

Research on the development of new lightweight Al–Li alloys using a selective laser melting process has great potential for industrial applications. This paper reports on the development of novel aluminum–lithium alloys using selective laser melting technology. Al–Cu–Li–Mg–Ag–Sc–Zr pre-alloyed powders with lithium contents of 1 wt.%, 2 wt.% and 3 wt.%, respectively, were prepared by inert gas atomization. After SLM process optimization, the microstructure and mechanical properties of the as-printed specimens were investigated. The densifications of the three newly developed alloys were 99.51%, 98.96% and 92.01%, respectively. They all had good formability, with the lithium loss rate at about 15%. The as-printed alloy with 1% Li content presented good comprehensive properties, with a yield strength of 413 ± 16 MPa, an ultimate tensile strength of 461 ± 12 MPa, and an elongation of 14 ± 1%. The three alloys exhibited a layered molten pool stacking morphology and had a typical heterostructure. The columnar crystals and equiaxed fine grains were alternately arranged, and most of the precipitated phases were enriched at the grain boundaries. The change in Li content mainly affected the precipitation of the Cu-containing phase. When the Li content was 1 wt.%, the following occured: θ phase, T1 phase and TB phase. When Li increased to 2 wt.%, T1 and T2 phases precipitated together. When Li reaches 3 wt.%, δ' phase precipitated with T2 phase. This study provides useful guidance for the future SLM forming of new crack-free and high-strength Al–Li alloys. [ABSTRACT FROM AUTHOR]

Q690 steel is widely used as building steel due to its excellent performance. In this paper, the microstructure evolution of the heat-affected zone of Q690 steel under simulated high heat input welding conditions was investigated. The results show that under the heat input of 150–300 kJ/cm, the microstructures of the heat-affected zone are lath bainite and granular bainite. The content of lath bainite gradually decreased with the increase in heat input, while the content of granular bainite steadily increased. The proportion of large-angle grain boundaries decreased from 51.1% to 40.3%. Overall, the average size of original austenite increased, and the precipitates changed from Ti (C, N) to Cr carbides. During the cooling process, the nucleation position of bainitic ferrite was from high to low according to the nucleation temperature, and in order of inclusions at grain boundaries, triple junctions, intragranular inclusions, bainitic ferrite/austenite phase boundaries, twin boundaries, grain boundaries, and intragranular inclusions at the bainitic ferrite/austenite phase interface. The growth rate of bainitic ferrite nucleated at the phase interface, grain boundary, and other plane defects was faster, while it was slow at the inclusions. Moreover, it was noted that the Mg-Al-Ti-O composite inclusions promote the nucleation of lath bainitic ferrite, while the Al-Ca-O inclusions do not facilitate the nucleation of bainitic ferrite. [ABSTRACT FROM AUTHOR]

This paper reviews quantitative characterization via transmission electron microscopy (TEM) and its application to interfacial phenomena based on the results obtained through the studies. Several signals generated by the interaction between the specimen and the electron beam with a probe size of less than 1 nm are utilized for a quantitative analysis, which yields considerable chemical and physical information. This review describes several phenomena near the interfaces, e.g., clear solid–vapor interface (surface) segregation of yttria in the zirconia nanoparticles by an energy-dispersive X-ray spectroscopy analysis, the evaluation of the local magnetic moment at the grain boundary in terms of electron energy loss spectroscopy equipped with TEM, and grain boundary character dependence of the magnetism. The direct measurement of the stress to the dislocation transferred across the grain boundary and the microstructure evolution focused on the grain boundary formation caused by plastic deformation are discussed as examples of material dynamics associated with the grain boundary. Finally, the outlook for future investigations of interface studies, including the recent progress, is also discussed. [ABSTRACT FROM AUTHOR]

The power conversion efficiency (PCE) of single-junction perovskite solar cells (PSCs) has reached 26.1% in small-scale devices. However, defects at the bulk, surface, grain boundaries, and interfaces act as non-radiative recombination centers for photogenerated electron-hole pairs, limiting the open-circuit voltage and PCE below the Shockley–Queisser limit. These defect states also induce ion migration towards interfaces and contribute to intrinsic instability in PSCs, reducing the quasi-Fermi level splitting and causing anomalous hysteresis in the device. The influence of defects becomes more prominent in large-area devices, demonstrating much lower PCE than the lab-scale devices. Therefore, commercializing PSCs faces a big challenge in terms of rapid decline in working performance due to these intrinsic structural defects. This paper provides a comprehensive review of recent advances in understanding the nature and the classification of defects, their impact on voltage losses, device parameters, intrinsic stability, and defect quantification and characterization techniques. Novel defect passivation techniques such as compositional engineering, additive engineering, post-treatments, dimensionality engineering, and interlayer engineering are also reviewed, along with the improvements in PCE and stability based on these techniques for both small-area devices and large-area roll-to-roll coated devices. [ABSTRACT FROM AUTHOR]

GH3536 and GH4169 nickel-based superalloys are widely used in aerospace engines and other hot-end components. In this paper, GH3536 and GH4169 alloy samples were fabricated by optimizing the process parameters using selective laser melting(SLM), the defect characteristics and microstructure of two alloys, as well as the effects of different homogenization temperatures and holding times on microstructure evolution, average grain size, and properties of two alloys were studied. The defect characteristics and microstructure were investigated by OM, SEM, and EDS, et al. The Vickers hardness meter was used to test the alloy's microhardness. The results indicate that the as-built GH3536 alloy exhibits more defects, including pores, cracks, and lack of fusion, while only pores are present in as-built GH4169 alloy. The melt pool of alloy is eliminated by homogenization treatment, and the grains grow into equiaxed grains. m23C6 are found to distribute within grain boundaries and grain interiors of GH3536 alloy, while NbC are found to distribute within grain boundaries and grain interiors of GH4169 alloy, and the amount of precipitates is significantly reduced with the increase of homogenization temperature. The average grain size of GH3536 alloy is increased by 106.8% from 48.5 -m at 1130 t/1 h to 100.9 m at 1250 t/4 h . The grain size of GH4169 alloy is increased by 53.3% from 57 m at 1080 t/1 h to 87.4 m at 1200 t/4 h.The homogenization treatment of GH3536 alloy and GH4169 alloy results in a significant decrease in microhardness of the former, from 262HV to 180-190HV, while the latter shows a significant increase, from 313HV to 430-450HV. [ABSTRACT FROM AUTHOR]

GH3536 and GH4169 nickel-based superalloys are widely used in aerospace engines and other hot-end components. In this paper, GH3536 and GH4169 alloy samples were fabricated by optimizing the process parameters using selective laser melting(SLM), the defect characteristics and microstructure of two alloys, as well as the effects of different homogenization temperatures and holding times on microstructure evolution, average grain size, and properties of two alloys were studied. The defect characteristics and microstructure were investigated by OM, SEM, and EDS, et al. The Vickers hardness meter was used to test the alloy's microhardness. The results indicate that the as-built GH3536 alloy exhibits more defects, including pores, cracks, and lack of only pores are present in as-built GH4169 alloy. The melt pool of alloy is eliminated by homogenization treatment, and the grains grow into equiaxed grains. m23C6 are found to distribute within grain boundaries and grain interiors of GH3536 alloy, while NbC are found to distribute within grain boundaries and grain interiors of GH4169 alloy, and the amount of precipitates is significantly reduced with the increase of homogenization temperature. The average grain size of GH3536 alloy is increased by 106.8% from 48.5 m at 1130 t/1 h to 100.9 m at 1250 t/4 h. The grain size of GH4169 alloy is increased by 53.3% from 57 m at 1080 t/1 h to 87.4 m at 1200 t/4 h.The homogenization treatment of GH3536 alloy and GH4169 alloy results in a significant decrease in microhardness of the former, from 262HV to 180-190HV, while the latter shows a significant increase, from 313HV to 430-450HV. [ABSTRACT FROM AUTHOR]

The control of phase balance has always been a tough challenge for the welding of duplex stainless steel, which heavily restricts its optimal serving performance in engineering. The microstructure development and mechanical characteristics of SAF2205 plasma arc welded joints were thoroughly examined in this paper. It was proven that the phase balance can be well controlled by plasma arc welding, and the austenite content of the welded joints was about 60%. Despite successful phase control, there was still grain coarsening and distortion; i.e., at the center of the welded zone, the gain size was about eight times that of the base metal, and the austenite was mainly in the form of grain boundary austenite and intragranular austenite, while more Widmanstatten austenites were found in the heat-affected zone. In addition, a transition region between the heat affected zone and the center exhibited columnar ferritic grains. Furthermore, the plasticity and toughness of the welded joints were significantly decreased, especially the elongation in the longitudinal direction, which is about 10% lower than that of the base metal, and transversal tensile strength remained comparable to the base metal, with only a slight reduction in longitudinal tensile strength. Lastly, the formation mechanism of microstructure and its correlation with mechanical properties were revealed. This investigation offers valuable insights into the structural integrity of duplex stainless steel welded joints in engineering applications. [ABSTRACT FROM AUTHOR]

The study of the effects of impurity on grain boundaries is a critical aspect of materials science, particularly when it comes to understanding and controlling the properties of materials for specific applications. One of the related key issues is the segregation preference of impurity atoms in the grain boundary region. In this paper, we employed the on-the-fly machine learning to generate force fields, which were subsequently used to calculate the segregation energies of phosphorus and silicon in bcc iron containing the ∑5(310)[001] grain boundary. The generated force fields were successfully benchmarked using ab initio data. Our further calculations considered impurity atoms at a number of possible interstitial and substitutional segregation sites. Our predictions of the preferred sites agree with the experimental observations. Planar concentration of impurity atoms affects the segregation energy and, moreover, can change the preferred segregation sites. [ABSTRACT FROM AUTHOR]

The aim of the present paper is to investigate the microstructure of laser-melted surface layers of austenitic steel for biomedical applications. The surface of prismatic specimens from AISI 321 stainless steel was treated by continuous CO2 laser. Three modes of laser processing were used, ensuring surface melting. The microstructure was observed by OM and SEM, while the chemical composition was investigated by EDX analysis. It was found that the microstructure of as-delivered steel was two-phase and relatively inhomogeneous in morphology and chemical composition. It consisted of austenite with grain sizes between 20 - 150 µm, relatively large amount of striped δ-ferrite and spherical carbides along the grain boundaries. After laser melting, the microstructure remained two-phase (δ-ferrite and austenite), but became more homogeneous in morphology and composition. Different dendrites morphology in the particular regions of the molten layer was confirmed - fine equiaxed dendrites on the top surface and columnar at the bottom of the molten pool. Delta-ferrite is located in the interdendritic areas and in larger amounts in the transition zone between the molten layer and the base metal. [ABSTRACT FROM AUTHOR]

Al–Si–Mg alloys are most commonly used to produce parts by laser powder bed fusion for several industrial applications. A lot of papers have already focused on the effects induced by conventional heat treatments on the microstructure and mechanical properties of AlSi10Mg alloys, rather than on AlSi7Mg. Nobody has investigated thermal stability during long-term direct and artificial aging heat treatments of AlSi7Mg. This study investigates the changes in mechanical properties induced by long-term exposure (512 h) at 150 and 175 °C (the operating temperature of AlSi7Mg) after (i) the laser powder bed fusion process performed on a pre-heated build platform (150 °C), and (ii) heat treatments to the solution at 505 °C per 0.5 and 4 h. Thermal stability was evaluated through both Vickers microhardness measurements to obtain the aging profiles, and tensile tests to evaluate the mechanical properties in specific conditions. An optical microscope was used to investigate the microstructure. It was found that aging at 175 °C confers the same effects induced by a secondary aging heat treatment on as-built samples and, simultaneously, the worst effects on the solution heat treated AlSi7Mg alloy after long-term exposure. The AlSi7Mg DA at both 150 °C and 175 °C showed the same Vickers microhardness (~95 HV0.5), UTS (~300 MPa), and YS (~200 MPa) values for the longest exposure times because the fine and cellular α-Al matrix confers higher stiffness and strength despite the over-aged conditions. On the other hand, the coarsening effects that affected the precipitates during aging at 175 °C, as well as the formation of the precipitate-free zones along the grain boundaries, justified the highest detrimental effects induced on the SHTed samples. [ABSTRACT FROM AUTHOR]

Magnesium alloys with high damping, high specific strength and low density have attracted great attention in recent years. However, the application of magnesium alloys is limited by the balance between their mechanical and damping properties. The strength and plasticity of magnesium alloys with high damping performance often cannot meet the industrial requirements. Understanding the damping mechanism of magnesium alloys is significant for developing new materials with high damping and mechanical properties. In this paper, the damping mechanisms and internal factors of the damping properties of magnesium alloys are comprehensively reviewed. Some damping mechanisms have been studied by many scholars, and it has been found that they can be used to explain damping performance. Among existing damping mechanisms, the G-L dislocation theory, twin damping mechanism and interface damping mechanism are considered common. In addition, some specific long-period stacking ordered (LPSO) phases' crystal structures are conducive to dislocation movement, which is good for improving damping performance. Usually, the damping properties of magnesium alloys are affected by some internal factors directly, such as dislocation density, solute atoms, grain texture and boundaries, etc. These internal factors affect damping performance by influencing the dissipation of energy within the crystal. Scholars are working to find novel damping mechanisms and suitable solute atoms that can improve damping performance. It is important to understand the main damping mechanisms and the internal factors for guiding the development of novel high-damping magnesium alloys. [ABSTRACT FROM AUTHOR]

This paper presents characterization and modeling results exploring the temperature dependence of the electrical characteristics of 3-D NAND Flash strings. Experimental data over a wide temperature range are used to calibrate a Technology Computer-Aided Design model for current transport through the polysilicon channel of the strings, which is then used to investigate the role of grain boundaries on string conduction. Results reveal that the variability in the grain configuration in the strings introduces a nonnegligible statistical spread in the temperature dependence of the threshold voltage (${V}_{T}$) of the memory cells, which acts as a broadening contribution to the array ${V}_{T}$ distribution when temperature is changed. The experimental and modeling activities will be extended in Part II of this paper to explore the temperature dependence of the ${V}_{T}$ instability caused by random telegraph noise. [ABSTRACT FROM AUTHOR]

As the service performance requirements for metal components in diverse high-tech industries continue to escalate, a myriad of specialized operational environments pose increasingly formidable challenges to the comprehensive performance of various components. To address these challenges and further enhance the mechanical properties of 316L stainless steel, expand its application range, we have developed in-situ TiC reforced 316L composites. In this paper, we propose a novel method for the fabrication of grain boundary-dispersed, in-situ generated TiC-reinforced 316L metal matrix composites (MMC) through laser melting deposition (LMD), leveraging the decomposition reaction of Ti 3 SiC 2. Samples with different TiC contents were prepared, and their microstructures post-LMD were closely analyzed. Furthermore, the underlying enhancement mechanism of in-situ TiC on the mechanical properties of these samples was thoroughly investigated. The results demonstrate that the in-situ TiC particles are uniformly dispersed along grain boundaries, functioning as additional nucleation sites. This enhances the nucleation rate significantly and contributes to grain refinement. Compared with pure 316L material, the hardness and wear resistance of the composite material are greatly improved, and the hardness increased by up to 35.66 %. In-situ TiC can effectively improve the overall performance of 316L. [ABSTRACT FROM AUTHOR]

In this paper, the influence of antimony concentration and different sintering techniques on the structural, microstructural, and electrical properties of antimony-doped barium stannate, BaSn 1- x Sb x O 3 (BSSO, x = 0.00, 0.04, 0.06, 0.08 and 0.10) was investigated. BSSO-based ceramic samples were obtained by conventional and spark plasma sintering. The XRD analysis confirmed the single-phase, cubic BaSnO 3 lattice system in all conventionally sintered samples. Apart from the dominant cubic phase, the spark plasma sintering conditions led to the formation of a secondary phase, Ba 2 SnO 4 , in all samples. FESEM analysis revealed the presence of low angle grain boundaries (LAGBs) in BSSO samples with high antimony concentration (x = 0.08), independently of the sintering technique. However, the fraction of LAGBs is significantly higher in the BaSn 0.92 Sb 0.08 O 3 - SPS sample due to the simultaneous exposure of the conductive sample to the effects of high temperature and pressure during sintering process. These boundaries have low activation energy and allow free charge carrier transport through the grain boundary region. The high dopant concentration and the presence of large fraction of LAGBs in BaSn 0.92 Sb 0.08 O 3 - SPS sample reflected on its electrical properties through low and almost temperature-independent electrical resistivity in the temperature range of 25–150 °C. [ABSTRACT FROM AUTHOR]

ZnO linear resistors, due to its excellent performance, are widely used in numerous industries and gradually replacing traditional conductive resistors, presenting a broad prospect for application. To study the effects of lanthanide oxides on the microstructure and electrical properties of ZnO-based linear resistors, this paper prepared Dy 2 O 3 -doped ZnO-Al 2 O 3 -TiO 2 -NiO based linear resistors using a solid-state sintering method. The results showed that proper doping of Dy 2 O 3 could inhibit the growth of ZnO grains, leading to more uniform grain growth. Additionally, doped with appropriate amount of Dy 2 O 3 could enhance the linear performance of ZnO linear resistors, reduce the grain boundary barrier height (φ b), and decrease dielectric loss. Linear resistors with nonlinearity coefficient (α) of 1.07, grain boundary barrier height (φ b) of 0.0934 eV and resistance-temperature coefficient (α T) of −5.39 × 10−3/°C were obtained. The doping of Dy 2 O 3 could improve the comprehensive performance of ZnO linear resistors, making the fabricated ZnO linear resistors are more suitable for working in high frequency electric fields. The study and analysis of Dy 2 O 3 doped ZnO linear resistors are of significant importance for the preparation of high performance ZnO linear resistors. [ABSTRACT FROM AUTHOR]

In recent years, the use of "near-net forming" to manufacture key components of aeroengines has become a mainstream development direction. In this paper, "near-net forming" of rotating parts such as disks and shafts is realized by using axial closed die rolling (ACDR) deformation technology. Numerical simulation and experimentation research were utilized to compare the plastic deformation characteristics and microstructure evolution of TC11 disc component forming by upsetting and ACDR forming, including strain distribution, temperature distribution, and microstructure evolution mechanisms. The FEM results revealed that during the ACDR process, the equivalent strain exhibits a radial distribution pattern with the center of contact area between the billet and upper die. The top surface of the billet was located in the severe plastic deformation zone and had better microstructure uniformity as a whole. In addition, ACDR forming enables continuous "near-net forming" at relatively low loads. The experimental results illustrated that ACDR formation is characterized by three types of deformation: radial tension, circumferential torsion, and axial compression, and at the same time, the overall strain is higher. As a result, the initial α size in the core was finer and exhibited an equiaxial shape, and the remaining areas of the grain were relatively fine and more uniformly distributed. The ACDR forming process can obtain a uniform and refined TC11 microstructure more efficiently. The TEM morphology observation of the ACDR specimens revealed that the lamella α-phase was bent, twisted, and fractured under the combined action of axial and shear stresses. The spheroidization models are primarily the globularization model of shearing lamellar structure the grain boundary splitting model, the termination migration globularization model, and the globularization model of Rayleigh instability. [ABSTRACT FROM AUTHOR]

ABSTRACT In this paper, the low‐cycle fatigue fracture behavior and life prediction of Cr–Ni–Mo–V gun steel at room temperature and 600 °C are studied. The results indicated that at room temperature and 600 °C, the Cr–Ni–Mo–V gun steel exhibited obvious monotonic softening and cyclic softening. This behavior could be attributed to the formation of dislocation networks, dislocation walls, dynamic recovery, and dynamic recrystallization. As the temperature increased, the failure mode gradually shifted from mixed transgranular and intergranular fractures to intergranular fractures possibly owing to the reduced grain boundary strength and easy oxidation of the grain boundary at high temperatures. In addition, the fatigue life prediction model considering the influence of temperature is established by using the energy dissipation quadratic function, offering a practical method to improve the fatigue performance evaluation of Cr–Ni–Mo–V gun steel at various temperature. [ABSTRACT FROM AUTHOR]

In this paper, we propose an effective method for doping WC into Ta-Hf-C ceramics to significantly enhance their densification and mechanical properties. An increasing WC doping amount from 0 to 20 at.%, enhances the densification of Ta-Hf-C ceramics from 92.4 % to 99.1 %. This is mainly due to the fact that the doping of WC effectively removes the harmful oxygen impurities from the ceramics, thereby increasing their sintering activity. Furthermore, the doping of WC plays an active role in the mechanical properties of the ceramics. The Ta-Hf-C doped with 15 at.% WC has the highest value of 36.41 GPa for nano-hardness due to the solid solution strengthening mechanism, while the highest Vickers hardness (38.75 GPa) and fracture toughness (3.76 MPa m1/2) appear in Ta-Hf-C doped with 20 at.% WC. The main toughness mechanism is W segregation at the grain boundary, enhancing grain boundary strength. [ABSTRACT FROM AUTHOR]

The enhancement of the mechanical properties of an alloy is often accompanied by a decrease in corrosion resistance. Therefore, in this paper, thermal-cold cycling (TCC) treatment was used to process 7075-T83 aluminum alloy to improve its corrosion resistance on the basis of ensuring its mechanical properties. Intergranular corrosion (IGC) and electrochemical tests combined with transmission electron microscopy observation were carried out to investigate the effect of TCC treatment on the microstructure and corrosion resistance of the 7075-T83 aluminum alloy. The results showed that the corrosion resistance of the alloy was significantly improved and the microstructure was well optimized after two TCC treatments. The IGC depth of the alloy was the shallowest, at 25.8 μm, and the corrosion current density and corrosion rate reached the minimum values of 0.00148 mA/cm2 and 0.0484 mm/a, respectively. In addition, the average diameter of the matrix precipitates was the smallest, the volume fraction was the highest, the thickness of the passive film formed on the surface of the alloy was the thickest, reaching 3.81 nm, which effectively resisted the erosion of Cl−, while the agglomeration and coarsening of the grain boundary precipitates and the size and the distance between them increased, exhibiting a discontinuous distribution, which blocked the anodic corrosion channel and hindered the corrosion progress, thus improving the corrosion resistance of the alloy. [ABSTRACT FROM AUTHOR]

Grain size has a significant impact on the superelasticity of alloys. Large-sized grains show superior superelastic properties because the grain boundaries are minimized and the grain constraints caused by triple junctions are reduced. Cyclic heat treatment (CHT) is commonly employed to generate subgrains, whose energy can be consumed to induce abnormal grain growth (AGG) and obtain large-sized grains. In this paper, the effects of adding Cu on the subgrain characteristics during AGG and microstructural evolution of FeMnAlNi-based superelastic alloys were systematically investigated. The addition of Cu reduced the temperature at which the γ phase precipitates and altered the morphology of the γ phase. After the dissolution of the refined γ phases, the average subgrain size became smaller and misorientation increased. These characteristic subgrain changes improved the driving force for AGG and accelerated the grain boundary migration rate. Due to the addition of Cu, the maximum grain size reached 28.2 mm. This study provides a new method for the preparation of FeMnAlNi-based superelastic alloys with large-sized grains. [ABSTRACT FROM AUTHOR]