By using a combination of experiments and molecular dynamics simulations, our studies show that the elastic response of silica glass to initial compression gradually changes from abnormal to normal with increasing quench pressure, helium content or alkali modifier added in the glass matrix. We uncovered the structural origin of the elastic anomaly in silica glass as localized structural transitions between motifs of different stiffness that are similar to those found in its crystalline counterparts. Pressure-quenching, helium-stuffing, or alkali-modifying plays a different role in changing the structure of silica glass, but all of the resulting structures reduce the propensity for such local structural transitions to take place, thus the degree of elastic anomaly. Our studies demonstrate that by processing in ways that gradually eliminates the elastic anomaly, the degree of silica glass to undergo irreversible densification can be eventually eradicated. This provides a solid foundation for the bottom-up design of new glasses with tunable structure and properties.

In this study, the time that molten magnesium is in contact with the aluminum insert before solidification was predicted by solving the conservation equations of mass, momentum, and energy during compound casting of dissimilar Al/Mg couples. For this purpose, a three-dimensional transient model and FLOW-3D software were utilized and distributions of temperature and velocity vectors in the fluid over time were obtained. Then, the contact time at the bottom, middle, and top of aluminum insert in its interface with the magnesium melt was calculated. The results of simulation show that the contact time decreases from about 1.7 s at bottom to 1.6 s at middle and 0.8 s at top of the interface, respectively. This is consistent with the experimental metallographic observations which indicate a decrease in the thickness of formed intermetallic compounds from bottom to middle and top of the Al/Mg interface.

The high-cycle fatigue (HCF) behavior is significantly affected by surface roughness, especially for high strength metal FV520B-I. However, with surface roughness effect, neither the fatigue property, nor the high-cycle fatigue life model about FV520B-I with surface roughness has been reported. In this paper, designed fatigue experiment using the specimen with different surface roughness is presented to study the effectiveness of the roughness to the fatigue. The observations of the fatigue crack initiation sites and the crack propagation. Then the high cycle fatigue behavior of FV520B-I affected by surface roughness is analyzed. The existing very-high-cycle fatigue life model is not well-fit for high-cycle fatigue model of FV520B-I. A NEW high-cycle fatigue life prediction model of FV520B-I, taking surface roughness as a main effective variable is proposed. The model is built up by a comprehensive use of experimental data and the traditional fatigue modeling theory. The new finding between the fatigue strength coefficient and stress amplitude, with surface roughness, is adopted, leading to a NEW modified life prediction model. Study on fatigue model of FV520B-I with surface roughness is a very beneficial effort in fatigue theory and fatigue engineering development.

Classical molecular dynamics (MD), along with a bond-order potential for GaAs, has been used to study threshold displacement energies (E d) of Ga and As recoils. Considering the crystallographic symmetry of GaAs, recoil events are confined in four unit stereographic triangles. To investigate the displacement energy’s dependence on crystallographic orientation, more than 3600 recoil events were simulated to uniformly sample values of E d. Various defect configurations produced at these low energy recoils and the separation distances of Frenkel pairs were quantified and outlined. For both Ga and As, the minimum, $E_{\rm{d}}^{{\rm{min}}}$ , is found to be 8 eV, but the maxima, $E_{\rm{d}}^{{\rm{max}}}$ , are 22 and 28 eV for Ga and As, respectively. The distribution of E d within unit stereographic triangles indicates that E d shows a weak dependence on the recoil directions, in contrast to other semiconductors. The average threshold displacement energy is 13 ± 1 eV, which is in excellent agreement with available experiments.

Laminate sheets attract increasing attention from researchers and engineers. In this paper, Al/Ti/Al laminate sheets were fabricated by using cryogenic roll bonding for first time. The edge defects, mechanical properties, and interface bonding of laminate sheets by cryogenic roll bonding technique were compared with these by room-temperature roll bonding technique. Results show that there are some edge cracks in laminate sheets by room-temperature roll bonding while they do not appear when subjected to cryogenic roll bonding. The ultimate tensile stress of laminate sheets by cryogenic roll bonding increases up to 36.7% compared to that by room-temperature roll bonding. When laminate sheets are rolled to 0.125 mm from 2.025 mm, the interfaces between Al and Ti layers are bonded well for both cryogenic roll bonding and room-temperature roll bonding. Finally, we discussed the improvement in edge quality and mechanical properties and the mechanism of interface bonding of Al/Ti/Al laminate sheets during cryogenic roll bonding.

The present investigation aims to explore the evolution of microstructure and mechanical properties in Zn–Cu–Ti alloys during severe hot-rolling deformation. Twin deformation and dynamic recrystallisation are two important deformation modes of Zn–Cu–Ti alloys during hot rolling at 300 °C. Twin deformation and dynamic recrystallisation (DRX) appear one after the other. They not only consume the deformation stored energy but also inhibit initiation and growth of cracks. The elongation rate of Zn–Cu–Ti alloys has a rising trend with the increase in hot-rolling deformation. It is mainly due to grain refinement caused by increasing the ratio of DRX and twin deformation. The tensile strength of Zn–Cu–Ti alloys is found to decrease with the increase in hot-rolling deformation. This is because the solid-solution strengthening effect of copper is weakened by more deformation-induced precipitation of ε phase (CuZn5). The solid-solution strengthening effect of copper plays an important role in the strengthening effect of Zn–Cu–Ti alloys.

Thermal stability of pulsed laser deposited (PLD) nanocrystalline tantalum was explored through in situ transmission electron microscopy (TEM) annealing over the temperature range of 800–1200 °C. The evolution of the nanostructure was characterized using grain size distributions collectively with electron diffraction analysis and electron energy loss spectroscopy (EELS). Grain growth dynamics were further explored through molecular dynamics (MD) simulations of columnar tantalum nanostructures. The as-deposited grain size of 32 nm increased by only 18% at 1200 °C, i.e., 40% the melting point of tantalum, conflicting with the MD simulations that demonstrated extensive grain coalescence above 1000 °C. Furthermore, the grain size remained stable through the reversible α-to-β phase transition near 800 °C, which is often accompanied by grain growth in nanostructured tantalum. The EELS analysis confirmed the presence of oxygen impurities in the as-deposited films, indicating that impurity stabilization of grain boundaries was responsible for the exceptional thermal stability of PLD nanocrystalline tantalum.

Microstructure and electrochemical behavior of stainless steel weld overlay cladding exposed to post weld heat treatment (PWHT) were investigated, wherein pitting and intergranular corrosion behaviors of the cladding material were evaluated by potentiodynamic polarization and double loop electrochemical potentiokinetic reactivation methods. The results indicated that inclusions, multiple element (Mn, Si, and Al) oxides distributed randomly in the cladding material with a size less than 1 μm. PWHT contributed to carbides precipitation along the δ/γ phase interface and the formation of Cr-depleted zone in the austenite phase. Inclusions acted as the pitting sites in the sample as welded. PWHT reduced the pitting potential and contributed to the formation of larger and deeper pits, which nucleated around the δ/γ phase interface primarily. Existence of carbides and Cr-depleted zone dominated the loss of intergranular corrosion resistance after PWHT.

The addition of Co to CuZr-based shape memory bulk metallic glass composites stabilizes the high temperature B2-CuZr and decreases its stacking faulty energy, which promotes an increase in ductility caused by an easier twinning formation. A similar effect is expected for TiCu-based alloys. The present work aims to investigate the effect of Co additions on the phase formation, mechanical properties, and thermal stability of rapidly solidified Ti–Cu-based alloys. Rods of six Ti–Cu-based compositions with different amounts of Co were prepared by Cu-mold suction casting and investigated by X-ray diffraction, differential scanning calorimetry, scanning electron microscopy, dilatometry, and compression tests. The results show that the addition of Co decreases the glass-forming ability of Ti–Cu-based alloys and stabilizes B2 Ti(Cu,Ni,Co) at room temperature. The Co-added alloys exhibit an almost identical phase formation and microstructure, but their mechanical behavior is completely different nonetheless, which is mainly connected with the different composition of the B2 phase. The addition of Co makes the stress-induced martensitic transformation of this phase more difficult, which is one of the main reasons for the increase of the yield strength when a higher amount of Co is added.

The aqueous corrosion resistance of TiC–Ni3Al based cermets was examined with the specific aims of assessing the influence of both the raw materials and the test methods, using a 3.5 wt% NaCl containing solution. The effects of W contamination in the ceramic phase was investigated using a single-phase ceramic, with and without W, and with a stoichiometric intermetallic Ni3Al binder. The influence of the electrolyte O2 content was examined for TiC cermets with 30 vol% binder, for both the stoichiometric composition and sub-stoichiometric variants, containing either Zr and B (alloy IC50) or Zr, B and Cr (alloy IC221) additions. Electrochemical measurements were matched with chemical and microstructural analyses at various stages of oxidation, and the rate of material loss in combination with the corrosion mechanisms were identified. The effects of O2 concentration were most significant for the TiC based cermets with Ni3Al due to the diffusion controlled nature of the reaction.

Shot-peened CM400 maraging steel was used to study the mechanism of enhanced notch fatigue properties of ultra-high strength materials. After shot peening, the specimen surface became rougher, but the transversal machining traces were reduced. The yield strength was slightly improved while the ultimate tensile strength and hardness maintained constant; as a result, the fatigue limit was promoted by about 1.5 times. The nucleated sites of the fatigue fracture were partly changed from the surface to subsurface/interior of the specimen. To further analyze the influencing factors of fatigue properties, the fatigue damage process may be resolved to two aspects: (a) fatigue damage rate affected by shear deformation and (b) fatigue damage tolerance controlled by the dilatation fracture process. Considering the stress state near the notch tip, the hydrostatic stress and maximum shear stress are considered for better understanding these two aspects. It is observed that the fatigue damage tolerance increased while the fatigue damage rate decreased after shot peening. Therefore, the notch fatigue properties of CM400 maraging steels can effectively be improved.

Two novel porphyrins (5,10,15,20-tetra(3-(carboethoxymethyleneoxy)phenyl)porphyrin, H2TEPp and 5,10,15,20-tetra(3-(carboxymethyleneoxy)phenyl)porphyrin, H2TCPp) and their copper(II) porphyrins (CuTEPp, CuTCPp) were synthesized. With these porphyrins, four new porphyrin-sensitized TiO2 nanorod composites (H2TEPp/TiO2, H2TCPp/TiO2, CuTEPp/TiO2, and CuTCPp/TiO2) were prepared and characterized by methods of XRD, SEM, TEM, FT-IR, UV-vis DRS, nitrogen adsorption–desorption and fluorescence spectra. Besides, the photocatalytic activity and stability of the composites were assessed in the degradation of 4-nitrophenol (4-NP). The results indicate that the morphologies and structures of these composites are less influenced by the loaded porphyrins or copper porphyrins compared with the nanorods TiO2 (anatase). The porphyrin or copper porphyrin molecules are confirmed to bond on the surface of TiO2 through carboxyl group, which is beneficial to the electron transfer between porphyrin and TiO2. All composites exhibit enhanced photoactivities compared with the bare TiO2 nanorods. The possible reason is that the recombination of photoproduced electron–hole has been controlled effectively in these composites, which can be seen from their decreased fluorescence emission. The stability results of composites show that they still hold considerable photocatalytic activities after six cycling experiments.

Melt-SHS (self-propagating high-temperature synthesis), based on the SHS process and oxide reaction method, was used for preparation of TiB2/Al composites. The mass ratio of two reactants, Ti powder/TiO2, in initial powder mixture was varied from 0:1 to 1:0. The results showed that the 5 wt% TiB2/Al composites could be successfully produced by a reaction of aluminum powder, TiO2, and B2O3 in Al melt at 950 °C, while the reaction rate was slow. The addition of titanium powder helps to reduce the content of Al2O3 and destroy the coating structure of Al2O3 covered TiB2 particles, which leads to the acceleration of reaction process and improvement of particle concentration. A significant improvement was that TiB2 particles were dispersively distributed when the mass ratio of Ti powder/TiO2 was 2:3. As a result, the 5 wt% TiB2/Al composites fabricated by melt-SHS process with modified reactants ratio showed excellent tensile properties with the ultimate tensile strength as high as 114.24 MPa. Besides, the composite also showed superior ductility.

Ordered mesoporous carbons (OMCs) are appealing alternatives to conventional porous activated carbon applied to electronic energy storage and conversion devices. Nitrogen-doped OMC (NOMC) was prepared with a soft-template strategy directly using task-specific ionic liquid with dicyanamide anion as the nitrogen dopant, and utilized as supercapacitors for the first time. Compared with pristine OMC, NOMC showed excellent electrochemical capacitive behavior in 6 M KOH electrolyte. NOMC possessed a high specific capacitance of 427 F/g at a current density of 1 A/g and exhibited a stable cycle life (almost 98% retained at a current density of 5 A/g after 2000 cycles). The outstanding capacitive performance of NOMC was ascribed to the synergetic effects of its bimodal mesoporous structure, large specific surface area (1919 m2/g), and nitrogen doping (3.52 wt%), which help to accelerate the ion diffusion, increase the surface charge storage, and intensify pseudo-capacitive reactions.

Hydrogen embrittlement behaviors of a 22Mn–0.6C (mass%) twinning induced plasticity (TWIP) steel with the grain sizes of 21 μm (coarse grain) and 0.58 μm (ultrafine grain) were investigated by means of hydrogen precharging and subsequent slow strain rate tensile tests. The total elongation and fracture stress for both of the coarse-grained and ultrafine-grained specimens decreased by hydrogen charging. The area fraction of the brittle fracture surfaces in the ultrafine-grained specimen was much smaller than that in the coarse-grained specimen. Three-point bending test also showed that the reduction of the fracture toughness by the introduction of hydrogen was much smaller in the ultrafine-grained specimen than that in the coarse-grained specimen. It was concluded that the suppressed hydrogen embrittlement by grain refinement in the 22Mn–0.6C TWIP steel was probably due to the smaller hydrogen contents per unit grain boundary area in the finer grain-sized material.

NiAl-based nanocomposites were successfully fabricated by mechanical alloying proceeded vacuum-hot-pressing sintering, and the mechanical and tribological properties of the NiA–NbC composite were investigated. The results show that the nanostructured powder particles with the average size around 5 nm were successfully obtained by a high-energy-ball mill. After sintering, the composites were consisted of B2-ordered NiAl and NbC second phase, and the crystalline size of the NiAl phase was about 20 nm. The relative density, hardness, and compressive strength of nanostructured NiAl materials increased with increasing the Nb content, which can be attributed to the second phase hardening effect of in situ formed NbC particulates and fine grain strengthening of nanocrystalline NiAl phase. Thereafter, the friction coefficient of the NiAl–3NbC composite was lowered by the addition of silver and that is significantly lower than the NiAl intermetallic compound and NiAl–3NbC composite at elevated temperatures, which was attributed to the lubricating films formed in sliding process at elevated temperatures. While the wear rates of NiAl–3NbC–10Ag composites are higher than that of the NiAl–3NbC composites at each test temperature, especially at 500 °C and 700 °C, which might be attributed to the phase variations on the worn surfaces of the composites.

In the present work, various Mn amounts (up to 2 wt%) have been added into Al–Mn–Mg 3004 alloy to study their effect on the evolution of microstructure and elevated-temperature properties. Results showed that the dominant intermetallics are interdendritical Al6(MnFe) until to 1.5 wt% Mn. With further addition of Mn to 2 wt%, the blocky primary Al6Mn/Al6(MnFe) and high volume of fine Al6(MnFe) intermetallics form in the matrix, leading to the rapid increase on the volume fraction of intermetallics. After the precipitation heat treatment (375 °C/48 h), the precipitation of dispersoids increased with increasing Mn contents and reached the peak condition in the alloy with 1.5 wt% Mn, resulting in the highest yield strength and creep resistance at 300 °C. However, the elevated-temperature properties became worse in the alloy with 2 wt% Mn due to the lowest volume fraction of dispersoids and highest volume of dispersoid free zone.