Disks of commercial Al-1050 and ZK60A alloys were stacked together and then processed by conventional high-pressure torsion (HPT) through 1 and 5 turns at room temperature to investigate the synthesis of an Al–Mg alloy system. Measurements of microhardness and observations of the microstructures and local compositions after processing through 5 turns revealed the formation of an ultrafine multi-layered structure in the central region of the disk but with an intermetallic β-Al3Mg2 phase in the form of nano-layers in the nanostructured Al matrix near the edge of the disk. The activation energy for diffusion bonding of the Al and Mg phases was estimated and it is shown that this value is low and consistent with surface diffusion due to the very high density of vacancy-type defects introduced by HPT processing. The results demonstrate a significant potential for making use of HPT processing in the preparation of new alloy systems.

The effect of applied pressure on reactive hot pressing (RHP) of zirconium (Zr):graphite (C) in molar ratios of 1:0.5, 1:0.67, 1:0.8, and 1:1 was studied at 1200 °C for 60 min. The relative density achievable increased with increasing pressure and ranged from 99% at 4 MPa for ZrC0.5 to 93% for stoichiometric ZrC at 100 MPa. The diminishing influence of pressure on the final density with increasing stoichiometry is attributed to two causes: the decreasing initial volume fraction of the plastically deforming Zr metal which leads to the earlier formation of a contiguous, stress shielding carbide skeleton and the larger molar volume shrinkage during reaction which leads to pore formation in the final stages. A numerical model of the creep densification of a dynamically evolving microstructure predicts densities that are consistent with observations and confirm that the availability of a soft metal is primarily responsible for the achievement of such elevated densification during RHP. The ability to densify nonstoichiometric compositions like ZrC0.5 at pressures as low as 4 MPa offers an alternate route to fabricating dense nonstoichiometric carbides.

A novel approach of powder metallurgy processed, cost-effective, environmentally friendly material, rutile, is proposed as an alternate to the conventional titanium-di-oxide (TiO2) in the process of enhancing tribological behavior of aluminium (Al) based composites. Rutile, also possess good thermal stability which is essential for any material subjected to high temperature applications. The role of rutile (TiO2) in the enrichment of tribological and microhardness properties of aluminium based metal matrix composites is presented. Al matrix composite was reinforced with rutile (TiO2) to the proposed compositions (0, 4%, 8%, 12%, mass fraction) through powder metallurgy route. Wear test was done using pin-on-disc apparatus under dry sliding conditions. The preforms were then characterized using optical microscopy (OM), scanning electron microscope (SEM) and energy-dispersive x-ray spectrometer (EDS). Outcomes suggest that to increase in mass fraction of TiO2, sintered density of the preforms approaches the theoretical density. OM images ratify uniform dispersion of TiO2 implants within the Al matrix. TiO2 offers promising wear and microhardness properties to the proposed composites which attribute to a high dislocation density of deformed planes. Plastic shearing, in conformity with the propagation of shear cracks broke particles as loose fragments which reduces the effective area of contact between the sliding surfaces and reduces loss of material in Al–12% TiO2 composite. Mechanism of wear disclosed through SEM images and EDS patterns concludes that delamination and adhesion dominates the material removal.

Synchrotron radiation real-time imaging technology was performed to in situ study the Cu–Ni cross-interaction in Cu/Sn/Ni solder joints under temperature gradient during soldering. The direction of temperature gradient significantly influenced the Cu–Ni cross-interaction. When Ni was the hot end, both Cu and Ni atoms could diffuse to the opposite interfaces, resulting in the occurrence of the Cu–Ni cross-interaction at both interfaces. The consumption of the Cu cold end was abnormally large, whereas that of the Ni hot end was limited. When Cu was the hot end, only Cu atoms could diffuse to the opposite interface, resulting in the occurrence of the Cu–Ni cross-interaction only at the cold end. The Cu hot end was seriously consumed, whereas the Ni cold end was still intact. The interfacial intermetallic compounds were always thicker at the cold end than at the hot end, especially at the Ni/Sn cold end. Cu imposed more damaging effect than Ni under temperature gradient. Based on the atomic fluxes, a model was proposed to discuss the effect of temperature gradient on the Cu–Ni cross-interaction and the interfacial reactions in the Cu/Sn/Ni solder joints.

Petroleum coke (PC) is a low-cost and potential carbon source for electrochemical energy storage. To expand the utilization of PC in supercapacitor, PC-based activated carbons (PCACs) with heteroatoms-doped were prepared from PC by KOH chemical activation. The as-prepared carbon exhibited a high surface area (2326.4 m2/g) and hierarchical micro-mesoporous structure, resulting in a high specific capacitance (421 F/g at 1 A/g) and excellent rate performance in KOH electrolyte (217 F/g at 50 A/g). Meanwhile, to improve the high-rate capacitive performance of PCACs in H2SO4 electrolyte, functionalized activated carbon (HQ/PCAC-4) was prepared by physically adsorbing the hydroquinone (HQ) on PCACs. The HQ/PCAC-4 showed an unprecedented capacitance value of 300.2 F/g even at an ultrahigh current density of 50 A/g. In addition, the energy density of HQ/PCAC-4 in H2SO4 electrolyte reached 19.5 W h/kg. The high energy density and excellent rate performance ensured their prosperous application in high-power energy storage system.

Single- and double-hit hot compression tests were performed at 1030 °C and strain rate of 0.1 s−1 on Ti–13V–11Cr–3Al beta Ti alloy to investigate the flow behavior and mechanism of microstructural evolution during the interpass period. It was observed that the flow stress level and the extent of yield point phenomena (YPP) were increased by an increase in the grain size. After the first pass, the microstructure was bimodal of large deformed grains and small recrystallized grains formed by continuous dynamic recrystallization. The increase in the interpass time to 100 s, led to the decrease in the yield drop and extent of YPP. However, the further increase in the interpass time to 300 s would result in an inverse effect. A combination between static recrystallization and metadynamic recrystallization was found responsible for grain refinement in the samples subjected to the interpass times below 100 s. At longer interpass times, i.e., 300 s, grain growth increased the average grain size.

We introduce a method to measure accurately surface residual stresses in the pre-equilibrium state, which were generated in workpieces during the milling process. The method takes into account strain changes and uses the inverse calculation. Material in the stress layer was removed layer by layer, and the strain change on the opposite side of the machined surface was measured. We also consider the change of the bending moment caused by the changed neutral layer. The stress values were calculated from the last layer to the first layer, and the residual stresses generated by milling are measured. We created a finite element model of a real workpiece and the measured stress values were used as inputs for the model. The measuring method was validated using finite element analysis. We find that our measuring method can be successfully used in practice to measure surface residual stresses and it provides reliable indicators for evaluating the surface properties of machined workpieces.

The object of this paper is to propose a novel method to evaluate the maximum inclusion size in medium strength steel by ultrasonic fatigue testing. The inclusion sizes in the medium strength steel were evaluated by ultrasonic fatigue testing using the fatigue specimen with a large risk volume under water-cooling condition. To ensure fatigue specimens of medium strength steel fracture from the internal inclusion, heat treatment and oxynitrocarburization were conducted to increase the strength of the specimen and to protect the specimen from surface corrosion induced by cooling water. The results show that evaluation of the inclusion size by the proposed method is more accurate than traditional approaches, which are based on inclusion size characterization from arbitrary two dimensional cross sections. Additionally, as the method is based on fatigue testing in the ultrasonic frequency regime, it can be conducted in a reasonable amount of time.

Microstructures and austenite grain growth behavior of the alumina-forming austenitic (AFA) steel subjected to normalizing and annealing at various temperatures were investigated. A modified kinetic model of austenite grain growth was constructed based on consideration of the heating history. Abnormal growth of austenite grain occurs when the temperature is increased to 1473 K, and some special large particles of the precipitates located at grain boundaries form when the sample is normalized at the temperature of 1523 K. Both NbC and NiAl precipitates are identified using routine x-ray diffraction. The fitted data based on the kinetic model used and the consideration of the heating history is in agreement with the changes in the austenite grain growth in the AFA steel even when there is abnormal grain growth. The grain growth exponents are shown to be 2.85 and 2.42 for normalizing and annealing, respectively.

This paper presents the results of an experimental study of the effects of pressure on polymer chain alignments in poly(3-hexylthiophene) and [6,6]-phenyl C61-butyric acid methyl ester (P3HT:PCBM) blends that are used in bulk heterojunction organic photovoltaic cells (OPVs). The P3HT:PCBM blends on glass were subjected to pressure and annealing at 140 °C. The surface morphologies, nano-/micro-structures and the chain alignments were analyzed using atomic force microscopy techniques and grazing incidence x-ray scattering. The current–voltage characteristics of the resulting devices are also shown to change significantly with changes in the nano-/micro-structures. The polymer chains were aligned in the direction of the applied pressure (edge-on), which reduced the lamellae spacing between the polymer units and increased the degree of crystallinity. The increased crystallinity plays significant role in the current–voltage enhancements. The implications of the study are discussed for the design and control of the nano/microstructures of bulk heterojunction organic solar cells.

The refinement mechanism of alternating current pulse (ACP) on the solidification macrostructures of pure Al and the characterization of refining efficiency were investigated by embedding the wire mesh in the mold. The experiment results showed that ACP treatment during solidification led to the formation of fine equiaxed grain. There were remarkably differences with respect to the area of fine equiaxed zone inside and outside the tube. Lorentz force, induced melt flow and the rest of intrinsic effects of ACP inside and outside the tube were discussed in the present study. It demonstrated that the forced melt flow could lead to the columnar fragmentation and make the crystal nucleus on the mold wall fall off and drift in the liquid, leading to grain refinement. In addition, Reynolds number was suitable to characterize the refining efficiency of pure Al under ACP.

Carbon nanotube (CNT) reinforced A356 aluminum alloys cast nanocomposites containing lower CNT contents were successfully fabricated where the way of introducing diluted Al–8 wt% CNT master nanocomposite in A356 melts was used. The differential thermal analysis and x-ray diffraction results showed that aluminum carbide phases (Al4C3) were formed before Al melting. The formation of Al4C3 was then proved to improve the wettability of CNTs during Al melting. Effect of CNT addition on microstructure and mechanical properties of CNTs/A356 nanocomposites were investigated by optical microscopy, scanning electron microscopy, transmission electron microscopy, and universal tensile testing machine. The results showed that CNTs (<0.4 wt%) were well distributed in the CNTs/A356 nanocomposites. CNTs could greatly refine the microstructure of A356 alloy. The mechanical properties of CNTs/A356 nanocomposites were also enhanced by CNT addition. Fractography analysis revealed that CNTs were distributed uniformly throughout the fracture surface.

We calculate, compare, and discuss the charge transport properties through quasi fullerene C40 obtained in three different electrode–C40–electrode testbeds by employing density functional theory combined with nonequilibrium Green's function, to predict the electronic structure of molecular junctions formed from copper, silver, and gold electrodes. We investigate various metrics such as chemical potential of electrodes, density of states, transmission spectra, Mulliken population, and molecular projected self-consistent Hamiltonian eigen states to develop a novel insight about the varying transport phenomenon as the metallic part of the scattering region is modified. We conclude that all the junctions exhibit strong metallic character displaying ballistic conductance of order of more than G 0 accompanied by pronounced ripples in their conductance spectrum and small rectifying behavior in their current spectrum. This rectifying behavior is found to stem from the asymmetric shifting of orbital energies with changing bias voltage due to change in relative charge transfer through central molecule C40.

In this paper, numerical study was systematically conducted to analyze the shear banding evolution in bulk metallic glasses (BMGs) with various notches subjected to the uniaxial compression, and the relation between the notched configurations and compressive malleability was therefore elucidated. Free volume was used to be an internal state variable to depict the shear banding nucleation, growth and coalescence in the BMGs with the aid of free volume theory, which was incorporated into ABAQUS finite element method code as a user material subroutine. The present numerical procedure was firstly verified by comparing with the existing experimental data, and then parameter analysis was performed to discuss the impacts of notch shape, notch size, notch orientation, and notch configuration on the plastic deformability of notched samples. The present modeling will shed some light on the failure mechanisms and the toughening design of notched BMG structures in the engineering applications.

Layered transition metal dichalcogenides which are part of the two dimensional materials family are experiencing rapidly growing interest owing to their diverse physical and optoelectronic properties. Large area controllable synthesis of these materials is required for transition from lab scale research to practical applications. In this work, we present a single step chemical vapor deposition process for large area monolayer growth of molybdenum selenide (MoSe2). We also demonstrate controllable thermal conversion from molybdenum selenide to molybdenum sulfide.

This paper proposes a method for determining the mechanical properties (Young's modulus, Poisson's ratio, yield strength, and work hardening factor) of a material at a specific point using an indentation technique that utilizes a specially designed indenter in conjunction with an inverse problem and finite element analyses. The specially designed indenter combines the characteristics of spherical and conical indenters and can be used to produce multiple indentations at a single point. The feasibility of the proposed method for determining the local mechanical properties of a material was confirmed by detailed precision verifications in the ideal case and the worst case.

Various routes (unidirectional, cross, and three directions) normal and different speed rolling (DSR) are conducted on pure titanium sheet at 673 K and sequent 933 K annealing is followed. The results show that transverse direction (TD)-split double peak texture is kept during unidirectional rolling and a fiber basal texture is formed after cross and three-direction rolling. However, TD-split texture is preserved and rotates about 45° while the fiber basal texture is generated after cross and three direction rolling combining (DSTDR) DSR, respectively. This may be related to the changed strain path and induced shear deformation as well as thermal activation. Due to rotation of grains, the anisotropy of mechanical properties of Ti sheets decreases, especially in various DSR routes. Erichsen value is improved greatly in DSTDR specimens.

Ordered phases and ductility of Fe–6.5 wt% Si magnetic material were investigated under different rolling temperatures, and the constitutive equation of the warm deformation was established. The results show that at high rolling temperature, accompanying with the appearance of some shallow dimples, the intergranular fracture can be transformed into the quasicleavage fracture, which makes the ductility of warm-rolled sheets greatly improved. In the 450–650 °C rolling temperature range, the antiphase domains (APDs) of warm-rolled sheets are cut, the superdislocation density increases greatly with decreasing warm rolling temperatures, resulting in a decrease in APD sizes during warm deformation. Meanwhile, more B2 and DO3 ordered phases occurring in the matrix improve the long range order parameters, thereby significantly reducing ductility of the alloy. The work softening of Fe–6.5 wt% Si alloy is attributed to a contribution combining the sizes of APDs with ordered phases.

The glass-forming Ti75Zr10Si15 and Ti60Zr10Nb15Si15 alloys composed of nontoxic elements may represent new materials for biomedical applications. For this study, melt-spun alloy samples exhibiting glass–matrix nanocomposite structures were subjected to thermal oxidation treatments in synthetic air to improve their surface characteristics. 550 °C was identified as the most appropriate temperature to carry out oxidative surface modifications while preserving the initial metastable microstructure. The modified surfaces were evaluated considering morphological and structural aspects, and it was found that the oxide films formed at 550 °C are amorphous and consist mainly of TiO2; their thicknesses were estimated to be ∼560 nm for Ti75Zr10Si15 and ∼460 nm for Ti60Zr10Nb15Si15. The thermally treated sample surfaces exhibit not only higher roughnesses and higher hardnesses but also improved wettability compared to the as-spun materials. By immersion of oxidized samples in simulated body fluid Ca- and P-containing coatings exhibiting typical morphologies of apatite are formed.

Surface modification treatments, such as the plasma nitriding improve the tribological properties of AISI 420 stainless steel; however, the corrosion resistance is deteriorated. The DLC (Diamond-Like Carbon) coatings were not only having a low friction coefficient but also good wear and corrosion resistance. In this work, both the corrosion behavior and the adhesion of the DLC hard coating, deposited on nitrided and non-nitrided AISI 420 stainless steel substrates, were studied. The coatings were characterized by means of EDS and Raman. In addition, nitrided layer microstructure and the coatings were analyzed by SEM-FIB and XRD. Corrosion behavior was evaluated by the salt spray fog test and cyclic potentiodynamic polarization tests in NaCl solution. The adhesion was assessed using Rockwell indentation and scratch tests. The a-C:H film and nitrided layer thicknesses were about 2.5 μm and 11 μm respectively. The nitrided layer improved adhesion in both tests. The coated AISI 420 stainless steel proved to have excellent atmospheric corrosion resistance and a passive behavior over 1 V (versus SCE) in the electrochemical tests. The adhesion and the corrosion performance were improved when the coating was deposited after the plasma nitriding treatment.