The influence of temperature and strain rate on hot deformation behavior and microstructure of Cu–10Ni–3Al–0.8Si alloy was investigated. The true stress increased rapidly initially until it approached the peak values. The peak value of true stress and the Zener–Hollomon parameter decreased with the increase of temperature and the decrease of strain rate. The thermal activation energy of the alloy was about 396.57 kJ/mol, the processing map was established and the appropriate compression temperature was between 900 and 950 °C. The 〈001〉 and 〈011〉 fiber texture was the main type of texture. The increase of temperature or strain rate accelerated the formation of 〈001〉 fiber texture. Dynamic recrystallization nucleated and deformation bands formed at 750 °C. Recrystallization was accelerated with the increase of temperature and the decrease of Zener–Hollomon parameter. Both continuous recrystallization resulting from dynamic recovery and dynamic discontinuous recrystallization were softening mechanisms.

In the present study, the surface properties and the corrosion behavior of a nanocrystalline surface layer fabricated on 45 steel by electropulsing-ultrasonic surface treatment (EUST) were investigated. EUST offered the specimen a smooth (R a < 0.33 µm) surface layer with nanoscale grains and compressive stress by the synergistic effect of high-energy electropulsing processing and ultrasonic impact. Open-circuit potential, potentiodynamic polarization, and electrochemical impedance spectroscopy studies indicated that EUST-induced surface nanocrystallization decreased the corrosion susceptibility of 45 steel in 3.5 wt% NaCl aqueous solution, leading to a decrease in corrosion current density (i corr) by 55% and an increase in charge transfer resistance (R ct) by 36%. The enhancement in surface comprehensive mechanical properties and corrosion resistance can be explained in terms of the decrease in surface roughness, the extent of grain refinement and the change of stress state, which were closely related to the introduction of high-energy electropulsing processing.

A novel two-stage reheating process with new alloy design has been developed to improve the microstructure morphology of semisolid Al–Si casting aluminum alloy for thixoforming. The process consists of first reheating the material to the liquidus temperature, holding for 5 min, and then lowering to the predetermined two-stage reheating temperature between 843–863 K and holding for 10 min. The experimentally-obtained grain diameter, roundness, and the amount of liquid trapped within the solid phase were characterized, along with the microstructure obtained using the traditional feedstock reheating process. The Wilcox test (with α = 0.05) was then applied to statistically analyze the measured differences in the microstructures obtained using the two different processing routes. It was found that a refined near-spherical structure with uniform globule size, higher sphericity, lower coarsening rate constant, and less entrapped liquid was obtained via the new two-stage reheating process in comparison with the microstructure obtained using the traditional feedstock reheating process.

A key issue in two-dimensional structures composed of atom-thick sheets of electronic materials is the dependence of the properties of the combined system on the features of its parts. Here, we introduce a simple framework for the study of the electronic structure of layered assemblies based on perturbation theory. Within this framework, we calculate the band structure of commensurate and twisted bilayers of graphene (Gr) and hexagonal boron nitride (h-BN), and of a Gr/h-BN heterostructure, which we compare with reference full-scale density functional theory calculations. This study presents a general methodology for computationally efficient calculations of two-dimensional materials and also demonstrates that for relatively large twist in the graphene bilayer, the perturbation of electronic states near the Fermi level is negligible.

The aim of this study is to prevent cracks in large foam bodies prepared by thermo-foaming of alumina powder dispersions in molten sucrose. Cracks initiate in the binder burnout stage during which the bodies undergo shrinkage in the range of 32–49 vol% depending on sucrose content. Intermediate pyrolysis of the sucrose polymer binder prevents the cracking of large foam bodies as the carbon produced by pyrolysis binds the alumina particles during the initial stage of shrinkage and provides adequate strength to withstand the internal stresses produced during the pyrolysis and subsequent carbon burnout. The carbon bonded alumina foam bodies obtained after pyrolysis do not show any visible cracks during subsequent carbon burnout and sintering because the alumina particles establish a firm network with each other due to particle drag and rearrangement during pyrolysis of the sucrose polymer binder as evidenced from microstructure analysis. The carbon bonded alumina foam bodies show high compressive strength (2–1.3 MPa) and are amenable to machining operations such as milling and drilling without cracking.

A systematic study of SiC layer preparation in CH3SiCl3–Ar–H2 system by fluidized bed chemical vapor deposition was given. The phase, morphology, grain size, and crystal structure of the products were investigated based on series characterizations methods. Free silicon was formed at lower temperatures while free carbon was formed at higher temperatures. By introducing argon in the deposition system, silicon formation was suppressed and cauliflower structure with subordinate small particles was observed. The formation mechanisms of different microstructures were discussed. The experimental phase diagram of CVD SiC composed of three regions of SiC + Si, SiC and SiC + C was established and boundaries of the three regions were given. The phase diagram obtained can be used to guide the new applications of SiC series materials. The low-temperature dense SiC, porous SiC with tunable densities, small grained SiC, and composite SiC materials were prepared successfully, also it was indicated that SiC jointing technology can be developed based on the phase diagram accordingly in the future.

The article discusses the structure and properties of noncrystalline carbon films synthesized by ion-plasma sputtering of a graphite target in an argon atmosphere at direct current. Analysis of the molecular structure of carbon films was performed using Raman spectroscopy and dependence of the structure of synthesized films on the synthesis temperature and substrate material was revealed. Besides the main G peak possesses the values in a broad frequency range from 1500 to 1575 cm−1. The evolution of molecular structure peculiarities of synthesized carbon films depending on the synthesis conditions was clearly shown using the numerical methods of the Raman spectra decomposition. Studies of the optical spectra showed that the band gap of synthesized films varies from 0.78 to 1.67 eV and with increasing optical band gap, the value of G peak position decreases under laser excitation of 2.62 and 1.96 eV.

The microstructure, room temperature compressive property, and elevated temperature tensile property of directionally solidified NiAl–Cr(Mo)–(Hf,Dy) hypereutectic alloy were investigated. The directional solidifications of liquid metal cooling technique (LMC) and zone melted liquid metal cooling technique (ZMLMC) were adopted. In the LMC alloy, the well-aligned and fully eutectic lamellar structure parallel to the growth direction is obtained. The interlamellar spacing gradually decreases with increasing the withdrawal rate, and the compressive yield strength gradually increases. In the ZMLMC alloy, the eutectic lamellar structure is disordered and not parallel to the growth direction, and the quantities of Cr(Mo) primary phases are observed. Compared to the ZMLMC alloy, the LMC alloy has a better combination property because of the well-aligned lamellar structure. The observations of crack propagation and fracture surface are performed to better understand the fracture behavior.

An Fe–0.26C–1.96Si–2Mn with 0.31Mo (wt%) steel was subjected to a novel thermomechanical processing route to produce fine ferrite with different volume fractions, bainite, and retained austenite. Two types of fine ferrites were found to be: (i) formed along prior austenite grain boundaries, and (ii) formed intragranularly in the interior of austenite grains. An increase in the volume fraction of fine ferrite led to the preferential formation of blocky retained austenite with low stability, and to a decrease in the volume fraction of bainite with stable layers of retained austenite. The difference in the morphology of the bainitic ferrite and the retained austenite after different isothermal ferrite times was found to be responsible for the deterioration of the mechanical properties. The segregation of Mn, Mo, and C at distances of 2–2.5 nm from the ferrite and retained austenite/martensite interface on the retained austenite/martensite site was observed after 2700 s of isothermal hold. It was suggested that the segregation occurred during the austenite-to-ferrite transformation, and that this would decrease the interface mobility, which affects the austenite-to-ferrite transformation and ferrite grain size.

To study the hot deformation behavior of the Ti–22Al–25Nb alloy, isothermal compression tests were conducted at the temperature range of 930–1080 °C with strain rates of 0.001–1.0 s−1. Both the strain rate and the deformation temperature have a significant influence on the stress–strain behavior of the Ti–22Al–25Nb alloy. A hyperbolic–sine constitutive equation is established to quantitatively demonstrate the relationship between the parameters involved, and the hot deformation activation energy Q is determined as 621 kJ/mol. To optimize the processing window, a hot processing map is established, which is related to the microstructure evolution in hot working. The lamellar globularization as well as the dynamic recrystallization (DRX) would contribute to the stable regions with high power dissipation, while the adiabatic shear bands would lead to unstable regions. Moreover, an Avrami-type kinetics model is applied to examine the evolution of DRX during isothermal deformation process.

The pure and Er3+-modified binary Pb(Zn1/3Nb2/3)O3–9PbTiO3 (PZN–9PT) single crystals were grown by using the flux method. The phase structure of the as-grown single crystals at room temperature was confirmed by the x-ray diffraction analysis. The effect of Er3+ addition on the electrical properties and upconversion luminescence of PZN–9PT was investigated. The rhombohedral to tetragonal phase transition temperature and the Curie temperature of the Er3+-modified PZN–9PT single crystals were 370 and 451 K, respectively. The coercive field E C at room temperature was evidently higher by 11.6 kV/cm than that of the PZN–9PT single crystals (E C, ∼3.5 kV/cm). Furthermore, the green and red upconversion emission bands were obtained under the 980 nm excitation, which are related to (2H11/2, 4S3/2) → 4I15/2 and 4F9/2 → 4I15/2 transitions.

The oxidation behavior of bulk ZrSi2 at 700, 1000, and 1200 °C in ambient air has been investigated. Parabolic to cubic oxide layer growth kinetics was confirmed by weight gain measurements and the average oxide layer thickness was 470 nm, 6.7 µm, and 37 µm at 700 °C, 1000 °C, and 1200 °C, respectively, after 5 h oxidation tests. Evolution of compositionally modulated nano/micro structures was confirmed in the oxide layer. At 700 °C, Si diffusion resulted in discontinuous Si-rich oxide phases in amorphous Zr–Si–O matrix. At 1000 °C, complex multilayered structures such as fine and coarse irregular spinodal structures, wavy Si-rich oxide, and Si-rich islands evolved. At 1200 °C, additional nucleation of nanoscale ZrO2 particulate phase was observed. The spinodal structures were confirmed to be crystalline ZrO2 and amorphous SiO2, and the thermodynamic driving force for phase evolution has been explained by extension of liquid miscibility gap in the binary ZrO2–SiO2 phase diagram.

Dilute magnetic semiconductors are attractive due to their potential in spintronic devices. In this work, vanadium doped ZnO system has been studied to see its future as a dilute magnetic semiconductor. Vanadium doped ZnO thin films where vanadium percentage is 2, 3, and 5% are deposited by pulsed laser technique (PLD). The lattice parameter c derived from the (002) diffraction peak increases as vanadium content increases, suggesting vanadium substitution for Zn in ZnO lattice. Photoluminescence (PL) measurements at low temperature shows the emission peak at 3.30 eV which hint toward p-type doping in ZnO. X-ray photoelectron spectroscopy (XPS) results show that vanadium exists in V2+ and V4+ valence state, which is in agreement with the XRD and PL results and support the vanadium doped ZnO phase. The ferromagnetic behavior also supports the formation of vanadium doped ZnO phase in thin film samples.

Bulk cementite samples with chromium (Cr) concentrations of 0, 3.01, 6.03, 8.22, and 9.76 wt% were prepared by mechanical alloying and spark plasma sintering. The elastic modulus, elastic recovery, and hardness increased with increasing chromium content. The maximum microhardness was 1070.74 HV (Vickers hardness) and the maximum elastic modulus was 199.32 GPa using a nanoindentation device. The effect of different concentrations of Cr on the wear behavior of the cementite plowing depth, roughness, debris from the worn surfaces, and weight loss due to wear were measured using pin-on-disk tribometric equipment. It was found that both the morphology and the abrasion resistance of a surface worn by microcutting and microplowing increased markedly with increasing Cr content.

X-ray diffraction analysis, transmission electron microscopy, and thermodynamic calculation were used to investigate the effect of microstructural condition of austenite on the microstructural characteristics of the nanoscale bainite ferrite in a high carbon steel. As austenization temperature increases to 950 °C, there are a higher vacancy concentration and homogenized distribution level of the interstitial carbon atom in the austenite grains. The movement of more di-vacancies combination could encourage the generation of the γ → α embryo nucleus. The interstitial carbon atoms have a stronger inhibitory effect on the formation of the γ → α embryo nucleus and homogenized distribution of the interstitial carbon atoms are able to make the inhibitory effect exist everywhere in the austenite grains. In consequence, the bainite ferrite could only nucleate in a smaller area (several nanometers), and grow into slender laths in a smaller width and a larger length.

A scalable approach for synthesis of ultra-thin (<10 nm) transition metal dichalcogenides (TMD) films on stretchable polymeric materials is presented. Specifically, magnetron sputtering from pure TMD targets, such as MoS2 and WS2, was used for growth of amorphous precursor films at room temperature on polydimethylsiloxane substrates. Stacks of different TMD films were grown upon each other and integrated with optically transparent insulating layers such as boron nitride. These precursor films were subsequently laser annealed to form high quality, few-layer crystalline TMDs. This combination of sputtering and laser annealing is commercially scalable and lends itself well to patterning. Analysis by Raman spectroscopy, scanning probe, optical, and transmission electron microscopy, and x-ray photoelectron spectroscopy confirm our assertions and illustrate annealing mechanisms. Electrical properties of simple devices built on flexible substrates are correlated to annealing processes. This new approach is a significant step toward commercial-scale stretchable 2D heterostructured nanoelectronic devices.

The effect of solution treatment (ST) on the microstructure and mechanical properties of cast Al–3Li–1.5Cu–0.2Zr alloy was investigated. Results showed that the volume fraction of secondary phases (Al2Cu, Al3Li) decreased obviously after ST. It was found that the strengthening of Al–3Li–1.5Cu–0.2Zr alloy was a balance of the precipitation strengthening, residual phase strengthening and fine grain strengthening. The residual phase strengthening and fine grain strengthening decreased with increasing the solution temperature and time, while precipitation strengthening increased. After ST at 560 °C for 40 h, the elongation of Al–3Li–1.5Cu–0.2Zr alloy reaches the highest value of 22.1%. In addition, the tensile properties are up to the highest values, ultimate tensile strength of 359 MPa and elongation of 3.5% after optimal ST at 560 °C for 40 h followed by aging treatment.

A self-made die with large cross section (180.2 × 22.2 mm) for equal channel angular pressing (ECAP) was used to study the influence of two different pressing routes (C X and C Y ) on refining homogeneity of high-purity aluminum plates. Microstructures were investigated by optical microscopy (OM) and electron back scatter diffraction (EBSD) methods, and micro-hardness and tensile tests were taken to evaluate deformation degree across the cross section and mechanical properties, respectively. The results indicate that pressing routes of ECAP have a great influence on structure homogeneity of plate samples. The route C Y leads to fine grains with better homogeneity because the same deformation direction is taken through each pass. Coarse columnar crystals with 3–4 mm change to 68.6 μm nearly equiaxed grains and a strong cube texture forms after four C Y passes, and corresponding mechanical properties increase by a factor compared to as-cast plate.