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In this review we summarize our work on the destructive regime, the loss of superconductivity near half-flux quanta, and present new data on the possible observation of vortex–antivortex unbinding in ultrathin, doubly connected superconducting cylinders. These cylinders were prepared by evaporating a superconducting film onto a rotating quartz filament with a diameter as small as 100nm, which is comparable with or smaller than the zero-temperature superconducting coherence length, Formula Not Shown . For cylinders with a relatively large diameter, bound vortex–antivortex pairs induced by thermal fluctuation and the loss of superconductivity through the unbinding of these pairs above a critical temperature are expected. However, when the diameter of the cylinder becomes smaller than Formula Not Shown , superconductivity is lost near the half-flux quanta even in the zero-temperature limit. We argue that this unique quasi one-dimensional system provides a link between one- and two-dimensional superconductors.

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We present a study of the sharp peak that develops near the ab-plane orientation in the angular dependent critical current of YBa₂Cu₃O₇ (YBCO) films. This peak arises from correlated pinning associated to intrinsic pinning by the layered structure of the YBCO, and from extended planar defects. We measure films produced by pulsed laser deposition (PLD) and metal organic deposition (MOD) on ion beam assisted deposition––MgO, and by PLD on single crystalline substrates. We show that the width and height of the peak increases with the out-of-plane mosaic spread of the films. We discuss the implications of the different structures (columnar and laminar respectively) of the PLD and MOD films.

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The superconducting microstrip and coplanar wave guide delay lines fabricated with YBCO/LaAlO₃ thin films of 35mm in diameter are described in the paper. The design, fabrication and experimental results are also presented. The insertion loss and delay time were measured with HP 8510. At 77K, insertion loss of 5ns microstrip delay lines is 0.12dB/ns at 1GHz, 0.55dB/ns at 5GHz, 1.2dB/ns at 10GHz. The insertion loss of 10 ns coplanar wave guide delay line is 0.19dB/ns at 2GHz, 0.44dB/ns at 4GHz, 0.63dB/ns at 6GHz.

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Aluminosilicate mesostructures (MSU-S_BEA) assembled from zeolite Beta (BEA) seeds exhibited relatively high hydrothermal stability and were significantly more active in the cracking of gas–oil compared to MCM-41 after severe steaming pretreatment. The MSU-S_BEA mesoporous materials with wormhole framework structure and those having morphology of solid nanoparticles with high interparticle mesoporosity were more steam-stable and more active after severe steaming than those with hexagonal pore structure. Differences in acid sites strength between the MSU-S_BEA materials and MCM-41 could not be probed by the complex reaction system of the large hydrocarbon molecules of gas–oil.

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In this paper, Co₃O₄/CeO₂ catalysts for steam reforming of ethanol (SRE) were prepared by co-precipitation and impregnation methods. The catalysts prepared by co-precipitation were very active and selective for SRE. Over 10%Co₃O₄/CeO₂ catalyst, ethanol conversion was close to 100% and hydrogen selectivity was about 70% at 450°C. The catalysts were characterized by X-ray diffraction, temperature-programmed reduction (TPR) and BET surface area measurements. The preparation method influenced the interaction between cobalt and CeO₂ evidently. The incorporation of Co ions into CeO₂ crystal lattice resulted in weaker interaction between cobalt and ceria on catalyst surface. In comparison with catalysts prepared by impregnation, more cobalt ions entered into CeO₂ lattice, and resulted in weaker interaction between active phase and ceria on surface of Co₃O₄/CeO₂ prepared by co-precipitation. Thus, cobalt oxides was easier to be reduced to metal cobalt which was the key active component for SRE. Meanwhile, the incorporation of Co ions into CeO₂ crystal lattice was beneficial for resistance to carbon deposition.

▼ Several solid acidic catalysts have been investigated for the Prins condensation of iso-butyl aldehyde with tert-butyl alcohol in a liquid-phase reaction. The results demonstrate that acidic molecular sieves are effective catalysts for the condensation reaction, and HZSM-5 molecular sieves possessed strong enough acidity and proper channel systems exhibit high catalytic performance. Solvent polarity and solvent-active site interaction would significantly affect the aldehyde conversion and the 2,5-dimethyl-2,4-hexadiene selectivity. The iso-butyl aldehyde to tert-BuOH ratio, catalyst amount, solvent amount, reaction temperature, reaction time, Si/Al ratio of HZSM-5 molecular sieves, catalytic performance of different solid acids, and side-reactions in the system are studied. Up to 78.6% iso-butyl aldehyde conversion is obtained with a 57.8% 2,5-dimethyl-2,4-hexadiene yield over HZSM-5 with Si/Al of 39 after 8h at 160^oC, which provides a useful and economical potential industrial application way on a large scale to manufacture 2,5-dimethyl-2,4-hexadiene.

▼ The hydrodesulfurization (HDS) of dibenzothiophene (DBT), tetrahydrodibenzothiophene (THDBT) and hexahydrodibenzothiophene (HHDBT) was studied over Co-MoS₂/γ-Al₂O₃ and Ni-MoS₂/γ-Al₂O₃ catalysts, and the HDS of 4,6-dimethyldibenzothiophene (4,6-DMDBT) over metallic Pt-Pd catalysts supported on mesoporous NaH-ZSM-5. The desulfurization of DBT at 300^oC was faster than that of THDBT and HHDBT, both over Co-MoS₂/γ-Al₂O₃ and Ni-MoS₂/γ-Al₂O₃. Desulfurization of THDBT occurred directly to CHEB and CHB, but desulfurization of HHDBT occurred mainly by dehydrogenation to THDBT and subsequent desulfurization of THDBT. In most cases C-S bond breaking occurred by hydrogenolysis. Pt-Pd/mesoporous NaH-ZSM-5 was much more active than Pt-Pd/γ-Al₂O₃, Pt-Pd/NaH-ZSM-5 and single metal Pt and Pd catalysts in the HDS of 4,6-DMDBT. The much higher rate of the Friedel-Crafts reaction of benzylalcohol with benzene demonstrated that mesoporous NaH-ZSM-5 had accessible mesopores. Noble metals on mesoporous zeolites are very active HDS catalysts and might be considered as catalysts in the second stage of a deep HDS process.

▼ In this paper, Mn-Ce/TiO₂ was prepared by sol-gel method and used for low-temperature selective catalytic reduction (SCR) of NO with NH₃ in the presence of SO₂ at different temperatures (100-200^oC). SO₂ had a poisoning effect on NO conversion of the Mn-Ce/TiO₂ catalyst and this effect was directly related with reaction temperature. The higher the reaction temperature, the more rapidly the catalyst activity decreased. The results of in situ diffuse reflectance infrared Fourier transform (in situ DRIFT) spectroscopy and temperature programmed desorption (TPD) profiles indicated that the active sites of the Mn-Ce/TiO₂ catalyst were seriously sulfated at 200^oC which led to an irreversible deactivation of the sample. While the formation and deposition of (NH₄)₂SO₃ and NH₄HSO₄ were the main causes of catalyst deactivation when the SCR reaction was carried out at 100^oC. This kind of deactivation could be almost completely recovered after water-washing treatment.

▼ The equilibrium controlled water dissociation and the kinetically controlled nitrous oxide (N₂O) decomposition were studied in the perovskite BaCo_xFe_yZr_1-x-yO_3-δ (BCFZ) oxygen-permeable membrane reactor. By increasing the temperature or pressure difference and by feeding reducing gases like methane or ethane to the permeate side to consume the permeated oxygen, hydrogen production rate or N₂O conversion could be enhanced. A hydrogen production rate of 3.1cm^3min^-^1cm^-^2 was obtained at 950^oC. When methane was used as the reducing gas on the shell side, the oxygen concentration on the N₂O side can be kept at a low level, thus avoiding the inhibition of the N₂O decomposition by adsorbed surface oxygen species. A complete decomposition of N₂O for gas streams containing 20vol.% N₂O was achieved on the core side at 850^oC. Simultaneously, methane on the shell side was converted into synthesis gas with CO yield of above 80%. When feeding ethane to the shell side, the hydrogen from the thermal dehydrogenation of ethane can consume the permeated oxygen. At 850^oC, an ethane conversion of 85% and an ethylene selectivity of 86% were obtained.

▼ The surface chemistry of NO_x on metal oxides is important to environmental catalysis. Here we employ plane-wave, supercell DFT calculations to characterize NO_x chemistry at the RuO₂(110) surface as a model of a catalytically active transition metal oxide surface. We identify a range of potential NO_x intermediates, and use a thermodynamic analysis to characterize their stability as a function of gas exposure conditions. Adsorbed NO (nitrosyl) and to a lesser extent NO₃ (nitrate) dominate the surface phase diagram. Computed vibrational spectra are in good agreement with observation and provide new assignments of observed surface species. NO₂ is thermodynamically unstable at the surface and its desorption is never favored: in contrast to its activity towards CO oxidation, RuO₂(110) is not an effective NO oxidation catalyst. Rather, it could be effective as a reversible NO adsorber. Finally, we characterize the kinetics of several NO surface reactions and identify a pathway that may contribute to the decomposition of NO to N₂ and N₂O over partially reduced surfaces.

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Misfit dislocations at YBa₂Cu₃O_7−δ (YBCO)/SrTiO₃ (STO) interfaces were studied to understand effects which could be responsible for the high interfacial J_c in YBCO thin films. In YBCO films with thickness ranging from 5 to 100nm, the interfacial structures (e.g. misfit dislocations) of YBCO/STO were investigated using moiré fringe contrast in plan-view transmission electron microscopy (TEM). The observed moiré pattern has a spacing of 17nm which corresponds to the lattice mismatch between the YBCO a lattice spacing and the cubic STO lattice constant. As the YBCO thickness reaches 100nm, twin structures dominate the image contrast. Our observations indicate that the moiré pattern originates from the lattice mismatch between the substrate and the orthorhombic phase of YBCO.

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A thin layer of SrTiO₃ has been successfully used as a buffer layer to grow high quality superconducting YBa₂Cu₃O_7−δ (YBCO) thick films on polycrystalline metal substrates with a biaxially oriented MgO template produced by ion-beam-assisted deposition (IBAD). Using this architecture, 1.5μm-thick-YBCO films with an in-plane mosaic spread in the range of 2–3° in full width at half maximum, and a critical current density over 2MA/cm² in self-field at 75K have been achieved routinely. More interestingly, we found the thickness of SrTiO₃ buffer layers strongly affects the properties of YBCO films. The critical current density of YBCO films increases dramatically when the thickness of SrTiO₃ buffer layer reaches an optimum range of 40–120nm. Microstructure studies, including transmission electron microscopy (TEM), X-ray diffraction (XRD) and scanning electron microscopy (SEM), and ion-milling experiments suggest that the YBCO texture evolution, STO outgrowths and STO surface dents are strongly related to STO thickness. They are the key factors for YBCO self-field J_c variation.

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The isothermal section of the Cu–Ti–Zr ternary system at 1023K has been constructed by using diffusion triple together with electron probe microanalysis, which consists of 15 single-phase fields, 25 two-phase fields and 13 three-phase fields. A ternary phase, Cu₂TiZr, is confirmed. Most of the Cu–Ti and Cu–Zr binary phases show large ternary solubility, in which Zr and Ti can substitute for each other to a certain degree. In addition, at 1023K, the CuTi₂ and CuZr₂ phase can form a continuous solution phase in the Cu–Ti–Zr ternary system.

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Different as-cast microstructures of an AlSi7Mg alloy were produced by controlling the solidification conditions. The as-cast grain size ranged from 1.4mm to 160μm and the morphology varied from dendritic to rosette-like to globular. The as-cast materials were then partially remelted and isothermally held at 580°C for microstructure evolution. The final microstructure depended on the initial as-cast microstructure and the isothermal holding time. After partial remelting and isothermal holding, coarse-grained dendritic structures were not able to evolve to a globular structure, while structures with medium sized dendritic grains evolved to a globular structure with a relatively large particle size after a long isothermal holding time. Fine-grained structures evolved to well-rounded globular grains within times ranging from 10min to 5min as the dendritic nature of the starting structure diminished. An empirical equation has been established to describe the relationship between the evolved microstructure and the as-cast microstructure.

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Numerous experimental results have suggested that the J_c of YBa₂Cu₃O₇ (YBCO) films is significantly higher near the film–substrate interface than in the remainder of the film. We previously proposed that this effect is due to interfacial pinning enhancement caused by stress and the resulting misfit dislocations at the heteroepitaxial interface. To test this hypothesis we have used a non-superconducting PrBa₂Cu₃O_7−δ (PrBCO) buffer layer to minimize the lattice mismatch with YBCO. We find that the PrBCO layers lower J_c of the 0.4μm YBCO films in a predictable way, and that, if sufficiently thick (∼0.5μm), they eliminate interfacial enhancement altogether. Our interpretation of this result is that the defects responsible for interfacial enhancement of flux pinning originate at the bottom of the non-superconducting PrBCO layer, which screens the pinning centers from vortices in YBCO. This result demonstrates that the pinning enhancement arises from stress at the film–substrate interface.

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The thermal diffusivity of YBa₂Cu₃O_7−x (YBCO) film was measured using the optical pump–probe method. A theoretical finite-difference model was employed to calculate the diffusivity value, and the best fit for the c-axis oriented YBCO film showed an average thermal diffusivity of 0.25±0.05mm²s⁻¹. The obtained result is compared to previous reports measured using various methods.

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We have investigated the microstructure and mechanical properties of sputter-deposited Cu/V and Al/Nb metallic multilayer systems in this study and compared their mechanical properties to Cu/Cr and Cu/Nb reported earlier. These multilayer films are all of fcc/bcc type, with Kurdjumov–Sachs orientation relationship: {111}fcc//{110}bcc; 〈110〉fcc//〈111〉bcc. In all cases, hardnesses of multilayers increase with decreasing layer thickness, and reach maxima at approximately 2–5nm layer thickness. The differences in their mechanical properties (the Hall–Petch slope and peak hardness) are interpreted in terms of their differences in shear moduli, heat of mixing, and characteristics of interfaces.

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Translucent Mg–sialon ceramics were prepared using spark plasma sintering (SPS) α-Si₃N₄ powders with 9wt% AlN and 3wt% MgO as sintering additives. Microstructural observations indicate that the optical and mechanical properties of Mg–sialon ceramics are affected by the density and α′:β′-phase ratio in sintered bodies, which are tailored by controlling the content of formed liquid phase and optimizing the parameters of spark plasma sintering in present study. The material is toughened by the existence of a small amount of β′-sialon. The reason that the two-phase composite does not greatly compromise optical property could be attributed to the fine equiaxed microstructures and low content of β′-phase. Translucent Mg–sialon ceramics achieving 66.4% of maximum transmittance, 21.4±0.3GPa hardness, and 6.1±0.1MPam^1/2 fracture toughness were prepared by spark plasma sintering at 1850°C for 5min.

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The fatigue behavior of reactor pressure vessel (RPV) steels during fatigue testing was monitored by an advanced, high-speed, high-sensitivity, nondestructive evaluation (NDE) technique called infrared (IR) thermography. Five stages of temperature profiles during fatigue were recorded: an initial increase of the mean specimen temperature followed by a temperature decrease, a constant (equilibrium) temperature region, an abrupt temperature increase, and a temperature drop after the specimen failure. Using the state-of-the-art IR camera, the temperature profiles were recorded cycle by cycle during 20 Hz fatigue testing. A theoretical model combining the thermoelastic, inelastic, and heat-conduction effects were used to explain and predict the temperature evolution during fatigue. Specifically, the temperature evolution was predicted, and the results were found to be in good agreement with the experimental data.

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The high-cycle fatigue behavior of 316 LN stainless steel (SS), the prime candidate target-container material for the spallation neutron source (SNS), was investigated in air and mercury at frequencies from 10 to 700 Hz with a R ratio of 0.1. A decrease in the fatigue life of 316 LN SS in air was observed with increasing frequency. However, little influence of frequency on fatigue life was found in mercury. An increase in the specimen temperature at 700 Hz seems to be the main factor that contributed to the decrease of the fatigue life in air, relative to that at 10 Hz. However, because of the cooling effect of mercury, only a small temperature increase was found at 700 Hz, and, therefore, there was little frequency influence in mercury. At 10 Hz, a shorter fatigue life of 316 LN SS was measured in mercury than in air at stresses greater than yield strength, which may have resulted from liquid metal embrittlement (LME). At lower stresses, no difference in fatigue lives between mercury and air was detected at 10 Hz. At 700 Hz, the fatigue life in mercury was longer than in air. The fatigue endurance limit measured at both frequencies in mercury and in air was approx. 350 MPa.

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In this study, attempts are made to obtain the approaches for quantitatively evaluating the notch sensitivity and the notch strength of polymethyl methacrylate (PMMA) glasses. Tension tests show that the unoriented PMMA glass is a low-ductility material and the oriented PMMA glass is a high-ductility one, and the orientation of PMMA glass greatly increases the fracture ductility. The notch sensitivity of PMMA glasses can be evaluated by the so-called notch sensitivity factor, which can be predicted from tensile properties. Test results and analysis show that the notch strength of PMMA glasses can be expressed by the equation for notch strength and predicted from tensile properties for the notched elements of PMMA glass with any given stress concentration factor. The orientation of PMMA glass decreases the notch sensitivity and increases the notch strength. It should be noted that PMMA glasses have higher notch sensitivity and lower notch strength than those of ductile metals because of the very low-elasticity modulus of PMMA glasses. It also shows the possibility of predicting the failure criteria with given survivability for PMMA glass notched elements in this paper.

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The evolution of the microstructure and mechanical properties of ultra-fine-grained and nanocrystalline Zn induced by ball milling at room temperature are studied systematically. The yield stresses measured from miniaturized disk bend tests and tensile tests are consistent with the microhardness results and generally increase with the decrease of average grain size. A dramatic decrease of hardness during milling from 1 to 3 h is a reflection of the increase of average grain size from 80 to 240 nm due to the initial unstable grain size and therefore, grain growth in this period. Young's modulus remains almost the same for samples milled for different times and is that for conventional grain size Zn. A transition from bending to membrane stretching is observed in the force–displacement curves for Zn ball milled for ≤18 h. The variation of transition strain with milling time could be related to the evolution of grain size distribution and therefore hardness during milling.

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CoCrFeNiTiAl_x (x values in molar ratio, x=0, 0.5, 1.0, 1.5 and 2.0) high-entropy alloys were prepared using a vacuum arc melting method. The effects of Al addition on microstructure and mechanical properties were investigated. The results show that only a face-centered cubic (FCC) crystal structure phase is observed in the CoCrFeNiTi alloy. The phase composition transforms to stabilized body-centered cubic (BCC) structure phases and typically cast dendrite structure appears when Al is added. The dendrite region is rich in Co, Ni, Ti and Al elements while the interdendrite region is rich in Fe and Cr elements. Subgrains and nanosized precipitates are observed in the as-cast CoCrFeNiTiAl alloy. These CoCrFeNiTiAl_x high-entropy alloys exhibit excellent room-temperature mechanical properties. For CoCrFeNiTiAl_1.0 alloy, the compressive strength and elastic modulus reach as high as 2.28GPa and 147.6GPa, respectively. High density of dimple-like structure is observed from the fracture surfaces of the Al₀ alloy, while alloys with Al addition show typical cleavage fractures with river-like patterns and cleavage steps.

▼ Al₂O_3p/Al composites were prepared by direct melt reaction process. The thermodynamics of in situ chemical reactions between molten aluminum and CeO₂ powder was studied. The XRD results show that the components of the as-prepared composites consist of Al₂O₃ and Al phases. For the as-cast composite specimens, SEM, EDX, TEM and SAD were used to analyze the reinforcement phases and interface characters of composites. The results show that the in situ generated Al₂O₃ particles, whose sizes are 100-200nm, have various irregular shapes and disperse uniformly in matrix. TEM observation shows that the interface between particle and matrix is clean. Furthermore, there is no fixed orientation relationship between Al₂O₃ particles and aluminum matrix. Only [12 10]//[111] orientation parallel relationship with low exponent is found. Therefore, the composites have isotropic properties. Besides characters mentioned above, there are large amount of high density dislocations and the generated extensive fine subgrains around Al₂O₃ particles. These features are favorable for improving composite performances. As a result, the composites are comprehensively strengthened not only by Al₂O₃ particles, but also by the high density dislocations and fine subgrains.

▼ Low-cycle fatigue (LCF) behavior of Ti-2Al-2.5Zr was investigated at 298 and 673K. Cyclic stress response curves showed that initial cyclic hardening was followed by cyclic softening at 298 and 673K, while secondary cyclic hardening appeared when testing temperature increased to 673K. Ti-2Al-2.5Zr displayed higher LCF lives at 673K than those at 298K. Microstructural characterization with transmission electron microscopy (TEM) revealed that {101 0} prismatic slip was primary plastic deformation mode in Ti-2Al-2.5Zr fatigued at 298K. {12 11} pyramidal slip could be activated at high cyclic strain amplitude. Whereas, multiple slips were simultaneously operated on {101 0} prismatic and {12 11} pyramidal planes in the range of tested cyclic strain amplitudes at 673K. Plastic deformation mode changed from planar slip to wavy slip as testing temperature increased from 298 to 673K. The improvement of LCF life of Ti-2Al-2.5Zr could be attributed to the increase of plastic deformation homogeneity due to activating multiple slips at 673K.

▼ The effect of the basal texture on the mechanical behaviour of AZ31B magnesium alloy sheet is studied numerically using a recently developed Elastic Visco-Plastic Self-consistent (EVPSC) model, in which both slip and twinning contribute to plastic deformation. We simulate uniaxial tension within the sheet plane using starting textures having the basal poles tilted at varying degrees from the normal direction. It is found that increasing the tilt angle increases the uniform strain, but decreases the 0.2% proof strength and the R-value. The effect of texture on sheet metal forming is further assessed by calculating the limit strain under in-plane plane strain tension. It is demonstrated that the limit strain increases dramatically with decreasing intensity of the basal texture. The numerical results are found to be in good qualitative agreement with experimental observations.

▼ In this paper, transformation matrices are established to describe the orientation transformation of the planes and directions in a sample during multi-pass equal channel angular pressing (ECAP) processing. From this basis, the shearing characteristics associated with multi-pass ECAP processing in different processing routes are analyzed, and a new ECAP route expected to be more effective for grain refinement and particle redistribution is proposed. With the aid of transformation matrix analysis, it is demonstrated that route B_C involves a redundant strain process and, hence, is not very effective for particle redistribution but is useful for grain refinement. The experimental results prove that the new proposed ECAP route, called route B_C-UD2, is more successful for both grain refinement and particle redistribution. The established transformation matrix analysis method is helpful both in analysis of the shear characteristics of multi-pass ECAP processing and in the design of new ECAP routes.

▼ Dislocation patterns and their evolution in 316L stainless steel subjected to uniaxial stress-controlled cyclic loading with occurrence of ratchetting deformation were observed by transmission electron microscopy (TEM). The microscopic observations show that the dislocation patterns change from low density patterns such as dislocation lines and pile-ups to those with higher dislocation density such as dislocation tangles, veins, walls, and cells, when the macroscopic ratchetting strain progressively increases with the number of cycles. Although one or two kinds of dislocation patterns mentioned above are prevailing in most of the grains at certain stage of ratchetting deformation, other patterns can be also observed in some grains at the same time. The features of dislocation evolution presented during the uniaxial ratchetting deformation are summarized by comparing with the dislocation patterns observed during monotonic tension and symmetrical uniaxial strain-controlled cyclic loading. The uniaxial ratchetting of 316L stainless steel can be qualitatively explained by the observed dislocation patterns and their variation with the number of cycles.

▼ The in situ composites with the reinforcement volume fraction of 30vol.% and the C/ZrO₂ mole ratio of 0, 0.5 and 1.0 have been fabricated by using exothermic dispersion synthesis in an Al-ZrO₂-C system. The reaction mechanism and mechanical properties of the composites have also been studied. When the reinforcement volume fraction of the composites is 30vol.% and the C/ZrO₂ mole ratio is zero, the Al first reacts with ZrO₂ to produce the α-Al₂O₃ particles and the active Zr atoms, and then the Zr atoms react with Al to form the Al₃Zr blocks, which are distributed uniformly throughout the aluminum matrix. The ultimate tensile strength and elongation of the composites at room temperature are 215.2MPa and 3.0%, respectively. The fracture mechanism of the composite can be characterized by a crack nucleus initiating in the Al₃Zr blocks and then propagating to the interface because of the poor properties of Al₃Zr. With increasing the C/ZrO₂ mole ratios, the ZrC is formed previous to the Al₃Zr due to its lower Gibbs free energy, and its formation peak becomes bigger in the DSC curve. The amount of the Al₃Zr blocks decreases, which leads to the improvement in the tensile properties of the composites. When the C/ZrO₂ mole ratio is up to 1, the Al₃Zr blocks have almost disappeared in the composites. The reinforcements are composed of α-Al₂O₃ and ZrC. At the same time, the ultimate tensile strength and elongation increase to 245.4MPa and 8.0%, respectively. The tensile fracture surface is composed of fine ductile dimples.

▼ In this paper, the mechanical properties and the internal friction (IF) of high alloyed martensitic carbon steel were investigated. The relationships between the internal friction and mechanical properties of the steel containing 0.98wt.% carbon were researched using dilatometer, X-ray diffraction, Rockwell hardness and impact toughness. The samples were quenched and tempered in order to vary the concentration of carbon in solid solution in the martensite. The internal friction was measured in an inversed torsion pendulum with high vacuum using free decay method. The behavior of dislocations and their interactions with point defects were analyzed through the changes of the internal friction spectrum.