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Abstract: Flow stress behavior and microstructures during hot compression of delta-processed superalloy 718 at temperatures from 950 to 1100°C with strain rates of 10−3 to 1s−1 were investigated by optical microscopy (OM), electron backscatter diffraction (EBSD) technique and transmission electron microscopy (TEM). The relationship between the peak stress and the deformation conditions can be expressed by a hyperbolic-sine type equation. The activation energy for the delta-processed superalloy 718 is determined to be 467kJ/mol. The change of the dominant deformation mechanisms leads to the decrease of stress exponent and the increase of activation energy with increasing temperature. The dynamically recrystallized grain size is inversely proportional to the Zener–Hollomon (Z) parameter. It is found that the dissolution rate of δ phases under hot deformation conditions is much faster than that under static conditions. Dislocation, vacancy and curvature play important roles in the dissolution of δ phases. The main nucleation mechanisms of dynamic recrystallization (DRX) for the delta-processed superalloy 718 include the bulging of original grain boundaries and the δ phase stimulated DRX nucleation, which is closely related to the dissolution behavior of δ phases under certain deformation conditions. [Copyright &y& Elsevier]

Abstract: Flow behavior and microstructures of superalloy 718 were investigated by hot compression tests performed at temperatures ranging from 950 to 1100°C with strain rates of 10−3 to 1s−1. The dependence of the peak stress on deformation temperature and strain rate can be expressed by a hyperbolic-sine type equation. The activation energy for superalloy 718 is determined to be 443.2kJmol−1. A power exponent relationship between the peak strain and the Z parameter is obtained. Microstructure analysis shows that the dynamically recrystallized grain size is inversely proportional to the Z parameter. The nucleation mechanisms of DRX are closely related to the value of Z parameter. Under low Z conditions, DRX nucleation and development are mainly assisted by the formation of twins near the original grain boundaries. [Copyright &y& Elsevier]

Abstract: Microstructure evolution during dynamic recrystallization (DRX) of superalloy 718 was studied by optical microscope and electron backscatter diffraction (EBSD) technique. Compression tests were performed at different strains at temperatures from 950°C to 1120°C with a strain rate of 10−1 s−1. Microstructure observations show that the recrystallized grain size as well as the fraction of new grains increases with the increasing temperature. A power exponent relationship is obtained between the dynamically recrystallized grain size and the peak stress. It is found that different nucleation mechanisms for DRX are operated in hot deformed superalloy 718, which is closely related to deformation temperatures. DRX nucleation and development are discussed in consideration of subgrain rotation or twinning taking place near the original grain boundaries. Particular attention is also paid to the role of continuous dynamic recrystallization (CDRX) at both higher and lower temperatures. [Copyright &y& Elsevier]

Abstract: Cu2O–Cu cermets were prepared by a novel method, hot pressing mixed C and Cu2O powders, in which the conductor Cu was produced by the reaction between C and Cu2O (called as in-situ reduction-hot pressing method and presented as IRHP). Phase and microstructures of the cermets were characterized by X-ray diffraction, optical microscope, and scanning electron microscope. XRD analysis showed that the cermets only consist of Cu2O and Cu phases. Microstructural characterization of the cermets showed that the distribution of Cu phase is homogeneous throughout the Cu2O matrix. The mechanical properties were measured under a universal tester, and the compressive strength of the cermets with the same Cu content is 1.5 times higher than that of the samples prepared by hot pressing the mixed Cu and Cu2O powders directly (called as hot pressing method and presented as HP). [Copyright &y& Elsevier]

Abstract: Through-thickness texture gradient in AA 7055 aluminum alloy rolled plate has been investigated using the electron back-scattered diffraction (EBSD) technique. Quantitative analyses of texture in five layers from the surface to the center of the plate were performed. A pronounced texture variation through the plate thickness was found. In the center layer, a typical β fiber texture running from {112} <111> orientation through {123} <634> orientation to {011} <211> orientation was found. Near the surface, in contrast, shear type textures including {001} <110> orientation, {112} <110> orientation and {111} <110> orientation were dominating. In particularly, when the shear type textures reached the maximum in both intensity and content, the β fiber became minimums. [Copyright &y& Elsevier]

Abstract: A series of magnetic isothermal heat treatment of Alnico alloys (Alnico5 and Alnico8) in a 10T magnetic field were performed. It was found that the high magnetic field strongly influences the modulated microstructure. Our observation shows that high magnetic field can enhances the nucleation rate of spinodal decomposition in Alnico5 alloy, leads the decomposed particles finer, and also increases the volume fraction of ferromagnetic particles. The external magnetic field (H ext ) can also accelerate the atom diffusion and turn the diffusion direction to itself. The effect of both the E ext (the external magnetic field energy) and the E elast (the elastic energy) on modulated structure in a hypothetical A–B system was simulated by phase field method. The littler the E elast is, the bigger the E ext is, the decomposed ferromagnetic particles become smaller, and parallel along the direction of the external magnetic field. [Copyright &y& Elsevier]

Abstract: Al18B4O33w/CoxFeyBz composite powders were prepared through electroless plating CoxFeyBz alloy coating onto the surface of Al18B4O33 whiskers. The microstructure evolution of the CoxFeyBz coating and the relevant variations in the properties of Al18B4O33w/CoxFeyBz composite powders were investigated. Amorphous or nano-crystalline CoxFeyBz coatings with Fe content of up to 80at.% were obtained in a wide range of [Co2+]/[Fe2+] ratios. The presence of Fe2+ reduced the reaction efficiency because of flocculation and the resulted coverage effect. The morphology of the CoxFeyBz coatings changed slightly but crystallization occurred quickly after annealing at 400°C. The electrical resistivity of the CoxFeyBz coatings decreased dramatically after annealing at 400°C for less than 60min, but was maintained at 10−2 Ω·cm despite the further increase of the temperature. The high resistivity likely hindered the interface polarization; consequently, no dielectric relaxation was detected in the microwave band. The saturation magnetization of the CoxFeyBz coatings persistently increased as the heat treatment proceeded or as the temperature elevated, which contributes to the improvement of permeability. The difference in microstructure evolution and the variations in the properties of Al18B4O33w/CoxFeyBz were discussed, and the effects of composition were preliminarily identified. [Copyright &y& Elsevier]

Abstract: The effects of age-forming on microstructures and mechanical properties of 7050 Al alloy were investigated in this work. The alloy was subjected to age-forming as well as stress-free ageing at 160°C for 6, 12, 18 and 24h, and its microstructures were characterized by electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). It was shown that creep might lead to grain elongation during age-forming, and the applied stress induces the coarsening of precipitates in 7050 Al alloy. The texture in the alloy was also influenced by age-forming. Consequently, the differences in microstructures result in differences in mechanical properties of age-forming versus traditional stress-free ageing. The ultimate tensile strength of age-formed samples were slightly lower than that of stress-free aged samples, while the yield strength of age-formed samples were apparently lower than that of stress-free aged samples. Specifically, the elongation of samples age-formed displays apparently decrease. [Copyright &y& Elsevier]

Abstract: Deformed microstructure in AM60B Mg alloy under hypervelocity impact at a velocity of 5kms−1 were investigated through optical microscope, scanning electron microscope and transmission electron microscope. The results show that four deformed zones around the crater can be classified based on the different deformed microstructure, including ultrafine grain zone, ultrafine grain and deformation twin zone, high and low density deformation twin zones. The dislocation slipping, deformation twins and ultrafine grains are the dominant components in the four deformed zones, and the evolution of deformed microstructure is speculated based on the deformed microstructure observed in four zones. Slipping and twinning play a critical role for the formation of the dynamic recrystallized grains, and twinning-induced rotational dynamic recrystallization mechanism is thought to be the main mechanism for the formation of ultrafine grains. The microhardness and dynamic compressive strength in different deformed zones were measured, and the high microhardness and yield strength in ultrafine grain zone should be attributed to the strain hardening and grain refining. [Copyright &y& Elsevier]

Abstract: Deformed microstructure and mechanical properties of AM60B magnesium alloy under hypervelocity impact at a speed of 4kms−1 were studied through optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM) and indenter technique. The results show that the deformed microstructure below the crater can be classified as three zones, i.e. dynamic recrystallization zone, high density deformation twin zone and low density deformation twin zone. The refined and equiaxed recrystallized grains adjacent to the crater were formed, which should be attributed to the twining-induced dynamic recrystallization mechanism. The , deformation twins are confirmed through selected area electron diffraction (SAED) technique. The microhardness and yield strength in the deformed microstructure zone near the crater are much higher than that of the matrix, which should be attributed to strain hardening and grain refining. [Copyright &y& Elsevier]

Abstract: Fe/SiO2 composite particles were synthesized by hydrogen reduction of Fe2O3/SiO2 precursor, which was prepared by sol–gel method. A reduction temperature higher than 600°C is required for the complete conversion of Fe2O3 to Fe. Fe/SiO2 composite particles exhibit superior complex permittivity and permeability in the microwave band. A reflection loss higher than −70dB as well as a broad absorption band can be simultaneously obtained for Fe/SiO2-based coatings about 2mm in thickness, suggesting that the Fe/SiO2 composite particles are a promising candidate for high performance electromagnetic absorption materials. [Copyright &y& Elsevier]

Abstract: Al18B4O33w/Co composite particles were prepared successfully through electroless plating Co on Al18B4O33 whiskers. The growth behavior of the coatings, the effect of the process parameters and the electromagnetic properties of the prepared Al18B4O33w/Co composite particles were investigated. The reduced Co nucleated first on the pre-activated surface of the whiskers to form insular particles which then grew larger gradually and eventually merged together to form continuous coatings. The reaction rate increased but the mass gain decreased with the increase of the bath pH and the bath temperature. The crystallinity of the deposited Co decreased with the increase of phosphorous content as well as the bath temperature. The effect of loading is much weaker compare to that of bath pH and bath temperature. The permittivity and the permeability of the prepared Al18B4O33w/Co composite particles are markedly higher than those of the raw Al18B4O33 whiskers in microwave band. Relaxation resonance is found in the samples with thick Co coatings due to the presence of eddy current, which deteriorates the permeability of the Al18B4O33w/Co composite particles. [Copyright &y& Elsevier]

Abstract: Al18B4O33w/Co composite powders were prepared through electroless depositing Co on Al18B4O33 whiskers and the microstructure of the prepared composite powders was adjusted through heat-treatment. The included Co oxide is reduced and the density as well as the crystal perfection of the coatings is improved when annealed at 400°C in H2 atmosphere. An increase of 105 Sm−1 in conductivity together with an increase of 28% in Ms is obtained, resulting in a prominent increase of the permittivity and the permeability. The increase of permittivity, specifically the dielectric relaxation is attributed to the increase of conductivity. The increase of permeability is attributed to the increase of Ms and the microstructure evolution. The increase of electromagnetic parameters in 2–18GHz band is believed to enhance the electromagnetic wave absorbing performance of the Al18B4O33w/Co composite powders. [Copyright &y& Elsevier]

Abstract: Microstructural characteristics of 1Cr18Ni9Ti stainless steel impacted by GCr15 projectiles at a velocity of 2–6km/s was studied through the optical microscope, SEM, TEM and EBSD techniques. The experimental results show that the adiabatic shear bands beneath the crater are observed, and its width is ranging from 1 to 10μm. The deformation twins, martensite and intersection between them are observed simultaneously under the crater, which should be attributed to the high strain rate impact. The elongated subgrains with high aspect ratio are found in the shear band, while the melt-related microstructure is observed in the shear band. The heat converted from plastic work continuously increases the local temperature and thus leads to continued softening, even melting, in the material. According to the constitutive equation, the temperature calculated inside a shear band can be rose to the melting point of the material, which explains the melt-related microstructure observed inside shear bands simply. [Copyright &y& Elsevier]

Abstract: Deformation behavior and microstructure evolution of 7050 aluminum alloy were investigated by tensile tests conducted at different temperatures (340, 380, 420, and 460°C) with different strain rates of 1.0×10−4, 1.0×10−3, 1.0×10−2 and 0.1s−1. The results show that the stress level of the alloy can be presented by a Zener–Holloman parameter in a hyperbolic sine-type equation with the hot activation energy of 256.6kJ/mol. Ductile transgranular fracture transforms progressively into ductile intergranular (or inter-subgranular) fracture with the decrease of Z value. At the same time, the soften mechanism of the alloy during high temperature deformation transforms from dynamic recovery to continuous dynamic recrystallization with decreasing Z value. The main deformation mechanism is usual slipping when the alloy was deformed at high Z value. Grain boundaries sliding takes part in deformation with low Z value. Grain boundaries migration plays the role with medium Z value. [Copyright &y& Elsevier]

Abstract: SiCw/Co nanocomposite particles were prepared by electroless plating cobalt on SiC whiskers and the microstructure evolution of the plated coating was investigated by SEM and XRD. SEM images show that growth occurs on the surface of the clusters at the initial stage; as they grow larger, the clusters converge to form a continuous coating, which is actually stacking of cobalt clusters. After heat treated at 500 °C in a hydrogen atmosphere, the cobalt coating transforms from an amorphous to a crystalline state. The thermal stability of SiCw/Co composite is low because of the weak bonding between the substrate and the cobalt coating. The continuous coating aggregates to clusters through surface diffusion during heat treatment. [Copyright &y& Elsevier]