The effect of Co on element segregation and microstructure is investigated in the third generation Ni-based single crystal superalloys with 4, 8.5, and 11.5 wt% Co addition. The results show that the increase of Co content leads to a severe element segregation in as-cast microstructure. After heat treatment, the size of γ′ phase is slightly reduced with Co content increase. During the thermal exposure, the γ′ phase coarsens gradually but its coarsening rate decreases with increasing Co content. In addition, some acicular and blocky topologically close-packed (TCP) phases are precipitated in 4% Co and 8.5% Co alloys. However, no TCP phase can be found in 11.5% Co alloy. Finally, it may be concluded that although a higher Co content is harmful for the element segregation, it is beneficial to maintain the cuboidal morphology of γ′ phase, decrease its coarsening rate, and impede the precipitation of TCP phase.

The effects of different Gd additions on wear behavior of the T6 heat treated Mg–xGd–3Y–0.5Zr alloys were investigated. The wear tests were carried out using a Ball-on-flat type wear apparatus against an AISI 52100 type bearing steel ball counterface in the load range of 3–15 N, sliding speed range of 0.03–0.18 m/s, temperature range of 25–200 °C and at a constant sliding distance of 400 m. The results showed that the wear rate of the tested alloys increased with increasing sliding load. By increasing the wear temperature to 200 °C, the wear rate of the Mg–6Gd–3Y–0.5Zr alloy decreased by about 24%. At higher wear speeds, wear resistance of the alloys increased due to the formation of stable oxide layers on the worn surfaces. The alloy containing 12 wt% Gd exhibited higher wear resistance compared with the alloys containing lower Gd contents under the same conditions.

H3PW12O40/polymethylmethacrylate (PMMA)/polycaprolactam (PA6) nanofibrous membrane with a sandwich structure was prepared by electrospinning. Characterization with Fourier transformation infrared spectroscopy (FT-IR), energy-dispersive x-ray spectroscopy (EDX), and x-ray photoelectron spectroscopy (XPS) indicated that H3PW12O40 has been successfully loaded into the upper and bottom layers of the sandwich membrane and its Keggin structure was not destroyed. The photocatalytic efficiency of the sandwich membranes were much higher (≥87.2%) than that of H3PW12O40 only (15.6%) and H3PW12O40/PMMA composite nanofibrous membrane (11.6%) in the degradation of methyl orange (MO) under ultraviolet irradiation. It may be caused by two factors: one was the photoreduction mechanism induced by the electron donating from PA6 to H3PW12O40, the other was the double contact area between H3PW12O40 and MO due to the sandwich structure of the laminated membrane. What is noteworthy is that the sandwich membranes were stable in water, so that they could be easily separated from the aqueous MO solution and reused without appreciable losses in photocatalytic activity after three photocatalytic cycles. In view of this, H3PW12O40/PMMA/PA6 sandwich nanofibrous membrane is promising as a photocatalyst to remove organic pollutants from practical wastewater.

The fluctuation of material parameters and coupling effects of them have significant effects on cross-sectional deformation of rectangular tube in rotary draw bending process. So, in this research, a global sensitivity analysis (GSA) system was established based on the combination of Morris' GSA method and 3-D finite element method, and the reliability of the system is validated. Based on the system built, the sensitivity values of different material parameters combinations were analyzed. The results show that (i) the maximum cross-sectional deformation ratio decreases with the increase of Young's module E and strain hardening exponent n, while the effects of strength coefficient K, initial yield stress σS, and thickness anisotropy exponent γ on cross-sectional deformation are opposite to those of E and n, (ii) the groups which contain E and γ simultaneously show greater sensitivity and the effect of group only including E and γ on cross-sectional deformation is the most remarkable, while the most insensitive group in different combinations contains K, and (iii) mostly, the sensitivity values of coupling groups to cross-sectional deformation are larger than those of one-parameter groups.

Ultrasonic impact treatment (UIT) combined with high energy electropulsing (EP) was applied to low carbon steel to introduce severe plastic deformation on the surface. The investigation indicated that a strengthened layer with a maximum hardness of approximately 330 HV on cross section was obtained, in comparison with the hardness value of 260 HV resulted from UIT solely. Alongside with high hardness, the enhanced structure layer was extended to a distinguishing depth of 2 mm. Microstructure in the cross section revealed a crack-free superficial layer by EP-UIT and pearlite colonies here experienced morphology variations by redistribution and spheroidization of cementite. A 3 μm oxide layer consisting of amorphous oxide and nitride as well as MnFe2O4 and hematite crystalline was formed on the treated surface. Thermal and athermal effect of EP was the key factor in these phenomena and it is assumed that acoustic softening, electro plasticity, and thermal softening were engaged simultaneously.

Electrocatalysts for oxygen evolution reaction (OER) has been at the center of attention for water splitting reactions. In this article we have presented a methodology to significantly improve the OER catalytic efficiency of electrodeposited Ni3Se2 films. Specifically, the pristine Ni3Se2 on surface nanostructuring induced through electrochemical etching shows a remarkable decrease of overpotential (@10 mA cm−2) to 190 mV, making it as one of the best OER elecrocatalyst known till date. Through detailed structural and morphological characterization of the catalyst film, we have learnt that such enhancement is possibly caused by the increased surface roughness factor and electrochemically active surface area of the etched film. The morphology of the film also changed from smooth to rough on etching further supporting the enhanced catalytic activity. Detailed characterization also revealed that the composition of the film was unaltered on etching. Ni3Se2 film was also active for HER in alkaline medium making this a bifunctional catalyst capable of full water splitting in alkaline electrolyte with a cell voltage of 1.65 V.

The present study aims to investigate the effect of strain rate on volume fraction of martensite (VFM) in 304L austenitic stainless steel through dome test. Findings of this study show that martensitic transformation affects the deformation mode and formability of this material. Three strain rates are applied by controlling forming punch speed to conduct the stretching experiments and VFM is measured using magnetic saturation method. Results of the present study reveal that maximum VFM of 56% forms at the pole at low strain rates, whereas VFM of 47% is seen at high strain rates, and transforms in the region close to the flange. It is noted that blanks show good formability under low strain rate and poor formability at high strain rates. The relationship between VFM and strain rate, strain, percentage of shell reduction, equivalent of stress, and triaxiality are discussed. The experimental procedure is simulated and predicted findings show good agreement with the experimental results.

Thermal degradation of graphene based mineral oil lubricants was studied using thermogravimetric analysis (TGA). As-synthesized graphene sheets of 8, 12, and 60 nm thick and engine oil formulations 20W50 SN/CF and 20W50 SJ/CF were used for synthesizing various test samples. UV-Vis spectrophotometry, zeta potential, field emission scanning electron microscopy, and energy-dispersive x-ray spectroscopy were used to characterize the graphene sheets and the nanolubricants. TGA revealed that the onset temperature of oxidation for the SN/CF oil could be delayed by 13–17 °C in the presence of graphene. Moreover the rate of oxidation when the weight loss of oil in the presence of graphene reaches 40–20% could be delayed by more than 30 °C. Resistance to oil degradation depends strongly on the graphene nanoparticle size and concentration. TGA kinetics studies show that the base oils have higher activation energy (Ea) and the addition of graphene significantly reduces Ea.

The fracture toughness of NiAl single crystals is evaluated with a new method based on the J-integral concept. The new technique allows the measurement of continuous crack resistance curves at the microscale by continuously recording the stiffness of the microcantilevers with a nanoindenter. The experimental procedure allows the determination of the fracture toughness directly at the onset of stable crack growth. Experiments were performed on notched microcantilevers which were prepared by focused ion beam milling from NiAl single crystals. Stoichiometric NiAl crystals and NiAl crystals containing 0.14 wt% Fe were investigated in the so-called “hard” orientation. The fracture toughness was evaluated to be 6.4 ± 0.5 MPa m1/2 for the stoichiometric sample and 7.1 ± 0.5 MPa m1/2 for the iron containing sample, indicating that the addition of iron enhances the ductility. This effect is intensified with ongoing crack propagation where the Fe-containing sample exhibits a stronger crack resistance behavior than the stoichiometric NiAl single crystal. These findings are in good agreement with macroscopic fracture toughness measurements, and validate the new micromechanical testing approach.

The effect of nitrogen gas addition in Ar-based double-layer shielding gas on the impact toughness of welded ultra-ferritic stainless steel during an autogenous gas tungsten arc welding (GTAW) process was investigated. The nitrogen behavior was proposed. The microstructure, mechanical properties, and fracture surface morphology of the weld metals have been evaluated. More equiaxed crystals, refined grain, narrow HAZ width, and increased microhardness were produced with nitrogen addition. Experimental findings indicated that nitrogen diffused into HAZ and dissolved into weld pool. The solute distribution was changed thus bringing significant constitutional supercooling and decreased temperature gradient of weld pool, which contributed to fine microstructure. Impact toughness at room temperature was enhanced from 2J to 9J (welds), 5J–13J (HAZ). Ductile fracture zone was produced about 0.3–0.5 mm thickness distance from the weld surface. A significant increased impact toughness of weld metal was due to the refinement of microstructure and element addition.

Physical properties of In0.5(ZrMg)0.75Mo3O12, including the coefficient of thermal expansion, phase stability, hygroscopicity, and decomposition temperature have been thoroughly studied by in situ x-ray powder diffraction, Raman spectroscopy and thermal methods. These investigations show that In0.5(ZrMg)0.75Mo3O12 exists in a monoclinic phase (P21/a) at room temperature and transforms to an orthorhombic (Pbcn) phase at ∼82 °C. In the orthorhombic form this material presents intrinsic near-zero thermal expansion (−0.16 × 10−6 K−1) in the range between 100 and 500 °C. The phase is not hygroscopic, but starts to decompose into its constituent oxides at temperatures higher than 700 °C. In comparison to the end member phase ZrMgMo3O12 in the In2Mo3O12–ZrMgMo3O12 solid solution, In0.5(ZrMg)0.75Mo3O12 is less promising for near room-temperature applications due to the phase transition from monoclinic to orthorhombic slightly above room temperature. However, the orthorhombic phase of In0.5(ZrMg)0.75Mo3O12 has potential for applications that require zero thermal expansion at temperatures higher than 100 °C.

In the present work, we are investigating the electronic transport mechanism for antimony-doped tin oxide (ATO) ultrathin films produced by a colloidal deposition process (CDP) of nanocrystals synthesized via a solvothermal route in organic medium. The ATO ultrathin films were prepared from nanoparticles containing 9 mol% of Sb and the observed electrical resistivity at room temperature was 1.55, 1.10 × 10−1, and 1.83 × 10−3 Ω cm, respectively, for the 40, 45, and 71 nm films. X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and atomic force microscopy were carried out to investigate the films and electrical resistivity measurements taken in the four-probe mode with temperature ranging from −260 to 27 °C (13–300 K ± 0.1 K). Results show a good data fitting on Mott's two-dimensional (2D) noninteracting variable range hopping for the 45 nm thin film, which is not further observed for the ATO ultrathin films obtained from CDP.

In the present paper, 10 vol%TiC/Ti–6Al–3Sn–3.5Zr–0.4Mo–0.75Nb–0.35Si composite produced via in situ casting technique was tested in the temperature range from room temperature to 900 °C and much attention was paid on the microstructural evolution during high-temperature tensile test. It was found that the variation of microstructures in deformation zones with strain exhibited different trends at different temperatures. Below 600 °C, dislocation density increased with strain over the entire strain range. As temperature increased to 700 °C, dislocations proliferated rapidly in the initial deformation and then dislocation annihilated through dynamic recovery. Above 800 °C, the variation of microstructures in deformation zones with strain was similar to that at 700 °C at the beginning but at higher strain, dynamic recrystallization (DRX) occurred, leading to the formation of equiaxed microstructure. Microstructural evolution in deformation zones corresponded to the variation of tensile stress–strain characteristics with temperature, reflecting the hardening or softening feature of matrix. Dynamic recovery ascribed to the flow softening of the composite at 700 °C, while flow softening is owing to dynamic recovery and DRX above 800 °C. In addition, matrix softening should show different trends in different temperature ranges.

Zn–Ni alloy coatings were deposited on rolled copper foil via electro-brush plating with different micro-force. Surface morphologies, microhardness, roughness, and bending performance were characterized. Mechanisms and influences of electro–brush plating micro-force on coatings performances were investigated and revealed. With the increase of electro-brush plating micro-force, surface morphologies of coatings become smooth and dense, and the grain size was refined. Microhardness of coatings had a gradually increasing tendency when the increasing amplification was reduced. However, surface roughness of coatings as well as bending performance increased firstly and then decreased. The mechanisms of micro-force generation and action were explained by mechanics theory and principle model. Plastic deformation and work hardening are generated and performances are improved. Consequently, the performance of electro-brush plating coatings has a tight relevance with micro-force.

The flash allowance and upset allowance have significant effects on characteristics of flash butt welded RS590CL steel joints. The overheated zone (OZ) widths increased with flash allowance (δf) increase, and decreased as the upset allowance (δu) increased. The coarsened upper bainite was formed in interface zone (IZ) and OZ as δf increased. With increasing δu, the large plastic deformation occurred and the interface formability improved. The hardness in IZ was a little lower than that in its vicinity OZ due to some ferrite existence and dislocation amount decreased in IZ. The tensile strengths of flash butt welding (FBW) joints were in good match with base metal and the ductilities were lower. The maximum bending crack length was 0.68 mm which indicated that the bending properties of FBW joints were good. Under this experiment, relatively large δf (10–12 mm) and δu (5.5–6.5 mm) were recommended for the benefit of high quality FBW joints.