The joint of dissimilar metals between Mo2FeB2-based cermets and 316L stainless steel was welded by gas tungsten arc welding with no fillers. The weldability was investigated by plate rigid restraint cracking test and transverse rupture strength was measured by the three-point bending test. Microstructure of the weld joint was studied with scanning electron microscope, energy-dispersive spectrometer, X-ray diffractometer and differential scanning calorimeter, etc. Corrosion behavior was investigated by the potentiodynamic polarization test. Results revealed that weld solidification cracking susceptibility existed in the fusion zone. Coarse irregular complex ternary boride phase (M3B2) and hypoeutectic microstructure were formed in weld metal (WM). In heat affected zone (HAZ), a small number of M3B2 grains dissolved into the γ-Fe based binder, with growth and coalescence of the remaining M3B2 grains. Microhardness of HAZ increased slightly and WM presented the highest microhardness in the whole joint. Besides, potentiodynamic polarization test showed that WM had a better corrosion resistance than Mo2FeB2-based cermets, which can be attributed to the higher Cr content and relatively homogenous Mo distribution.

Lead-free ceramics (1 − x)(K1/2Na1/2)NbO3–xBi(Sc3/4Co1/4)O3 [(1 − x)KNN–xBSC] were prepared by the conventional solid-state sintering method. X-ray diffraction patterns show that the introduction of BSC into KNN system caused insignificant change in crystal structure. The composition with x = 0.015 has diphasic tetragonal and orthorhombic phases. Moreover, the grain size significantly dependent on the composition. The phase transition temperatures of orthorhombic–tetragonal (TO–T) and tetragonal–cubic (TC) decreased with increasing x from 0 to 0.025. The TO–T value of KNN–0.015BSC ceramic is close to room temperature, resulting in good electrical properties (d33 = 190 pC/N, kp = 40.3%, εr = 1494, tgδ = 0.026), with the Curie temperature TC = 321 °C. The combination of good piezoelectric properties and high TC makes these KNN–BSC ceramics suitable for elevated temperature piezoelectric devices.

Transmission electron microscopy (TEM) based orientation mapping has been used to measure the length fraction of coherent and incoherent Σ3 grain boundaries in a series of six nanocrystalline Cu thin films with thicknesses in the range of 26–111 nm and grain sizes from 51 to 315 nm. The films were annealed at the same temperature (600 °C) for the same length of time (30 min), have random texture, and vary only in grain size and film thickness. A strong grain size dependence of Σ3 (coherent and incoherent) and coherent Σ3 boundary fraction was observed. The experimental results are quantitatively compared with three physical models for the formation of annealing twins developed for microscale materials. The experimental results for the nanoscale Cu films are found to be in good agreement with the two microscale models that explain twin formation as a growth accident process.

Ca0.98Eu0.02Al1−4δ/3Si1+δN3 (δ = 0–0.36) red-emitting phosphors were prepared by carbothermal reduction and nitridation method with stable and inexpensive CaCO3 as Ca source. Optimal nominal composition was obtained at δ = 0.18, showing intense emission peaked at 625 nm and high external quantum efficiency of 71%. The emission wave length could be successfully tuned from 630 to 606 nm with increasing δ value. Ca0.98Eu0.02Al1−4δ/3Si1+δN3 phosphors provided two coordinated environments for Eu2+ ions, resulting in two fitted Gaussian peaks. Energy transfer from Eu2+ sites in Si-rich environments to those in Si/Al-equivalent modes has been confirmed by analysis of the decay curve of each peak. The decay behaviors suggested that energy transfer effect slowed with higher δ value. Finally, warm white light was created by combining as-prepared red-emitting Ca0.98Eu0.02Al0.76Si1.18N3 and yellow-emitting YAG:Ce3+ phosphors with a blue-emitting chip, exhibiting a color rendering index Ra of 91 at a low correlated color temperature of 3500 K with a luminous efficiency of 79 lm/W.

The dispersion of carbon nanotubes is one of the problems in the application of polymer nanocomposites. In this study, the effect of chemical functionalization of the carbon nanotube surface on the dispersion of the tubes within a polymer is reported. The effect of carbon nanotube weight loading on the properties of polymer membrane was also studied. Multiwalled carbon nanotubes were dispersed in Nafion® matrix by melt processing techniques to form nanocomposite membranes. The morphology, dc electrical conductivity, thermal stability, mechanical properties, and proton conductivity of these nanocomposites were investigated. Nitric acid functionalized carbon nanotubes were evenly dispersed with Nafion as observed by scanning electron microscopy. The measurements of mechanical properties indicate that this processing method and carbon nanotube loading can improve the modulus of the nanocomposites.

We investigated how coherent interfaces, between face centered cubic (fcc)/hexagonal close packed (hcp) systems, affect large strain deformation and fracture modes in hcp zircaloy aggregates with fcc hydrides. We derived 36 unique transformations related to coherent interfaces between fcc and hcp systems. We then used these orientation relations (ORs) with a dislocation-density crystalline plasticity formulation, a nonlinear finite-element, and a fracture approach that account for crack nucleation and propagation. We investigated how these ORs affect crack nucleation and propagation, dislocation density and inelastic slip evolution, stress accumulation, lattice rotation, and adiabatic heating. The predictions indicate that the physical representation of ORs affects local deformation and fracture behavior and are, therefore, essential for the accurate predictions of behavior at different physical scales in heterogeneous crystalline systems.

We compared the enhancement of photoactivity of transition metal ion (1 mol% Fe, Cu, Mn, and Zn) doped CeO2 nanocatalysts, and examined the effects of oxygen vacancies and the valence of the doped ions. The nanocatalysts were synthesized using a coprecipitation method and were characterized by x-ray diffraction, scanning electron microscopy, transmission electron microscopy, Brunauer–Emmett–Teller isotherm methods and Raman spectroscopy. The photocatalytic activities of these catalysts were tested using aqueous Rhodamine B (RhB) degradation under UV irradiation. The spherical CeO2 nanocatalysts had a mesoporous structure and ∼15 nm average particle size. The catalytic activity was closely related to the oxygen vacancies and the valence of the doped ions. An increase in oxygen vacancies of doped CeO2 decreased the photocatalytic activity. The photocatalytic activities of the catalysts decreased in the order: 1 mol% Fe > Cu > Mn > Zn > undoped CeO2. The 1 mol% Fe doped CeO2 degraded ∼92.6% of the RhB after 3 h of irradiation, and the degradation obeyed pseudo-first-order kinetics. Liquid chromatography–mass spectrometry indicated that the photodegradation of RhB was a stepwise oxidation process. Under continuous oxidation, over a long reaction time, the RhB was completely oxidized to its final products, such as water and carbon dioxide.

The aim of the present investigation is to identify the wear mechanisms of multilayer coated carbide tool under different machining conditions during turning of hardened AISI 4340 steel. The chemical vapor deposited multilayer coated (TiN/MT TiC,N/Al2O3) carbide tool was used. The worn surfaces of the cutting tools were examined under digital optical microscope, scanning electron microscope, and elemental analysis. The investigation results showed a strong correlation between the cutting conditions and tool wear. The cutting speed and feed rate ensure the dominant effects on the tool wear followed by the depth of cut and also the progress of tool wear were verified under different intervals of time. The flank and rake faces of the cutting tool were severely gouged by the hard particles of workpiece material exhibited abrasive wear phenomenon. Intermittently, chipping at cutting edge, notching and catastrophic failure modes were observed in continuous machining.

In this study, semi-solid slurry of AZ91–2 wt% Ca (AZ91–2Ca) alloy was prepared by gas bubbling and shaped by rheo-squeeze casting process. The results indicate that fine semi-solid slurry of AZ91–2Ca alloy could be obtained by gas bubbling within 30 s, with primary α-Mg particles having an average diameter less than 50 μm and average shape factor higher than 0.7. With the decrease of pouring temperature from 599 to 590 °C, both tensile strength and elongation of rheo-squeeze casting AZ91–2Ca alloy first increased and then decreased. The rheo-squeeze casting AZ91–2Ca alloy sample prepared at pouring temperature of 596 °C exhibited the peak tensile strength and elongation. Compared with conventional squeeze casting, the improvement in mechanical properties of rheo-squeeze casting AZ91–2Ca alloy was mainly attributed to the grain refinement strengthening, including the refinement and spheroidization of primary α-Mg particles and the refinement in the residual melt.

Five well-known Zr-based alloys of the systems Zr–Cu–Al–(Ni–Nb, Ni–Ti, Ag) (Cu = 15.4–36 at.%) with the highest glass-forming ability were comparatively analyzed regarding their pitting corrosion resistance and repassivation ability in a chloride-containing solution. Potentiodynamic polarization measurements were conducted in the neutral 0.01 M Na2SO4 + 0.1 M NaCl electrolyte and local corrosion damages were subsequently investigated with high resolution scanning electron microscopy (HR-SEM) coupled with energy dispersive x-ray spectroscopy (EDX). Both pitting and repassivation potential correlate with the Cu concentration, i.e., those potentials decrease with increasing Cu content. Pit morphology is not composition dependent: while initially hemispherical pits then develop an irregular shape and a porous rim. Corrosion products are rich in Cu, O, and often Cl species. A combination of low Cu and high Nb or Ti contents is most beneficial for a high pitting resistance of Zr-based bulk metallic glasses. The bulk glassy Zr57Cu15.4Al10Ni12.6Nb5 (Vit 106) and Zr52.5Cu17.9Al10Ni14.6Ti5 (Vit 105) alloys exhibit the highest pitting resistance.

Nominal compositions of In2Ti1−xTmxO5−δ, (0.0 ≤ x ≤ 0.2 and Tm = Fe3+ and Cr3+) were synthesized by ceramic route and characterized by relevant techniques. In2Ti1−xFexO5−δ samples were single phased isomorphic with In2TiO5 phase while Cr substitution has resulted in mixed phased compositions. Dynamic light scattering experiments showed the increase in proportion of smaller sized particles with the increase in extent of Fe substitution. Mössbauer spectra revealed that Fe exists in +3 oxidation state in substituted oxides. The band gap decreased from 3.2 (In2TiO5) to 2.1 eV (In2Ti0.8Fe0.2Ox−δ) and to 1.9 eV in case of Cr substitution (In2Ti0.8Cr0.2O5−δ) attributed to participation of Fe 3d/Cr 3d levels. Photocatalytic H2 generation was evaluated over the substituted oxides from water–methanol mixtures under UV–visible irradiation. The decreasing order of photocatalytic activity is as follows: 20% Fe (mol%) > 10% Fe > indium titanate ≈ 20% Cr > 10% Cr. The loading of Pt as cocatalyst on surface of most active photocatalyst, In2Ti0.8Fe0.2Ox−δ further enhanced the photocatlytic H2 yield.

The Oxide Dispersion Strengthened (ODS) materials are potential candidates as cladding tubes for Sodium-cooled Fast Reactors. The nano-oxides are finely dispersed within the grains and confer excellent mechanical properties to these alloys. Hence, assessing nano-particle stability under irradiation remains crucial to guarantee safe use of these materials. Although neutron irradiation remains a binding and challenging experimental study to conduct, difficulties can be overcome by ion beam processing. Ion beam processing of the ODS material allows to identify the radiation-induced Ostwald ripening as the mechanism governing the nano-particle response under irradiation. The result is the increase in size and a decrease in density of the finely dispersed Y2Ti2O7 nano-particles. Under neutron irradiation, radiation-induced Ostwald ripening appears to be less effective since a slight growth of nano-particles is observed. Further, our approach shows that nanoparticle growth kinetics should scale as φ1/3, φ being the radiation flux. This suggests that the low irradiation flux is at the origin of the slower growth kinetics of the neutron irradiated particles. Both neutron and ion irradiation induce a modification of the nanoparticles/matrix interfaces which are generally flat and sharp prior to irradiation and present steps after irradiation. This could alter the nano-particle coarsening during irradiation.

In the present work, the effect of pre-ageing temperature and time variations on the mechanical properties and electrical conductivity of the Retrogression and re-aging (RRA) treated 7050 has been investigated. The results reveal that the electronic conductivity and hardness of RRA-treated samples are sensitive to the pre-ageing tempers. The RRA-treated samples with 120 °C/2 h pre-ageing +180 °C/2 h retrogression +120 °C/24 h re-ageing temper can be tailored toward a good combination of strength and elongation, while the electrical conductivity of re-ageing samples is also higher than that of 120 °C/24 h pre-ageing RRA-treated samples. With an intermediate pre-ageing temperature of 80 °C/24 h RRA-treated samples possess a higher re-aged electronic conductivity, while no significant differences can be found between hardness of 120 °C/2 h and 120 °C/24 h pre-ageing RRA-treated samples. The variation of hardness and electronic conductivity during retrogression depends on the pre-ageing tempers. For under-aged sample, the retrogression hardness appears a stage of hardness increasing followed by a further decrease in hardness results, owing to disappearance of dissolving stage of fine GP zone and η′ phase during pre-ageing.

The crystal–melt interfacial free energy is an important quantity governing many kinetic phenomena including solidification and crystal growth. Although general calculation methods are available, it is still difficult to obtain the interfacial energies that differ only slightly due to anisotropy. Here, we report such a calculation of Al crystal–melt interfacial energy based on the general framework of the capillary fluctuation method (CFM). The subtle dependence of both the melting temperature and interfacial free energy at melting temperature on the crystal interface orientation was examined. For Al, the average melting temperature is obtained at 934.79 ± 5 K and the orientationally averaged mean interfacial free energy is 98.35 mJ/m2. In addition, the anisotropy of the interfacial free energy is found weak, nevertheless with the values ranked as γ100 > γ110 > γ111.

In the present work, Cu–Al alloys were processed by surface mechanical attrition treatment (SMAT) under both room and liquid nitrogen temperature (LNT) conditions. In contrast to room temperature (RT) SMAT, dynamic recovery and recrystallization were largely suppressed during the LNT process. A gradient microstructure was obtained due to the gradient strain and strain rate impacted onto the sample. Microhardness measurement showed that the hardness values gradually decreased from the top surface to the central region. The local hardness of the top surface layer of the LNT and RT SMAT Cu–4.5% Al samples reached maximum values of 1.52 and 1.28 GPa, respectively. The Cu–4.5% Al alloy exhibited an improved yield strength of ∼496 MPa and a higher ductility (compared with literature data of Cu–Al alloys synthesized traditional severe plastic deformation methods) of 15.4% after the LNT SMAT process. A brittle-ductile failure pattern was easily distinguished after fracture. Moreover, the LNT SMAT is a low-cost process with high productivity and can be applied to various types of metallic production.

Electrochemical reactions at both positive and negative electrodes in a nickel metal hydride (Ni-MH) battery during charge have been investigated by in situ neutron powder diffraction. Commercially available β-Ni(OH)2 and LaNi5-based powders were used in this experiment as positive and negative electrodes, respectively. Exchange of hydrogen by deuterium for the β-Ni(OH)2 electrode was achieved by ex situ cycling of the cell prior to in situ measurements. Neutron diffraction data collected in situ show that the largest amount of deuterium contained at the positive electrode is de-intercalated from the electrode with no phase transformation involved up to ∼100 mA h/g and, in addition, the 110 peak width for the positive electrode increases on charge. The negative electrode of composition MmNi3.6Al0.4Mn0.3Co0.7, where Mm = Mischmetal, exhibits a phase transformation to an intermediate hydride γ phase first and then to the β phase on charge. Unit cell dimensions and phase fractions have been investigated by Rietveld refinement of the crystal structure.

The nonisothermal crystallization kinetics, fragility, and thermodynamics of Ti20Zr20Cu20Ni20Be20 high entropy bulk metallic glass (HE-BMG) have been investigated by differential scanning calorimetry. The activation energies for the glass transition and crystallization events were determined by Kissinger and Ozawa methods. The value of local Avrami exponent is less than 1.5 in most cases for all the three crystallization events, indicating that the major crystallization mechanism is diffusion-controlled growth of pre-existing nuclei. The local activation energy is stable during the whole crystallization process and this further confirms that the crystallization occurs through a single mechanism. Ti20Zr20Cu20Ni20Be20 alloy can be classified into “strong glass formers” according to the estimated fragility index and also shows a relatively low value of Gibbs free energy difference. However, compared with Zr41.2Ti13.8Cu12.5Ni10Be22.5 BMG, the glass-forming ability of Ti20Zr20Cu20Ni20Be20 HE-BMG is much lower and the related reasons have been discussed.

This paper provides an overview of advanced scanning transmission electron microscopy (STEM) techniques used for characterization of irradiated BCC Fe-based alloys. Advanced STEM methods provide the high-resolution imaging and chemical analysis necessary to understand the irradiation response of BCC Fe-based alloys. The use of STEM with energy dispersive x-ray spectroscopy (EDX) for measurement of radiation-induced segregation (RIS) is described, with an illustrated example of RIS in proton- and self-ion irradiated T91. Aberration-corrected STEM-EDX for nanocluster/nanoparticle imaging and chemical analysis is also discussed, and examples are provided from ion-irradiated oxide dispersion strengthened (ODS) alloys. Finally, STEM techniques for void, cavity, and dislocation loop imaging are described, with examples from various BCC Fe-based alloys.

Fracture toughness testing of materials at the micrometer scale has become essential due to the continuing miniaturization of devices accompanied by findings of size effects in fracture behavior. Many techniques have emerged in the recent past to carry out fracture toughness measurements at the relevant micro and nanolength scales, but they lack ASTM standards that are prescribed for bulk scale tests. Also, differences in reported values arise at the microscale due to the sample preparation technique, test method, geometry, and investigator. To correct for such discrepancies, we chose four different fracture toughness test geometries in practice, all of them micromachined in the focused ion beam (FIB), to investigate the fracture toughness of Si(100) at the micrometer scale. The average KIC that emerges from all four cases is a constant (0.8 MPa m1/2). The advantages and limitations of each of these geometries in terms of test parameters and the range of materials that can be tested are discussed.

Microwave sintering is a novel and efficient technology for the rapid preparation of metallic materials. In this paper, an investigation has been performed on the distribution of microwave electromagnetic fields in a metallic particle system and its influence on sintering behavior. The results show that the microstructure of the “metallic-void” will induce a nonuniform distribution and focusing effect of electromagnetic fields during microwave processing, which may accelerate the sintering process. However, further study shows that the focusing effect will decline as the neck grows larger, and will also decline from outside to inside within the loosely packed powder system, which will result in the slowdown of the sintering rate. These results were supported by the synchrotron radiation computed tomography experimental observation of the microstructure evolution of metallic powders during an entire uninterrupted microwave sintering process.