Fused deposition modeling (FDM) 3D printing is an additive manufacturing process capable of rapidly building three-dimensional computer-modeled objects. The technology offers an inexpensive and efficient technique to manufacture customized objects with intricate geometries using a simple printing process. However, FDM is currently restricted in application due to a limited availability of functional materials. Research in the field has focused on incorporating functional characteristics into printable polymers to expand application of FDM technology. In this work, neutron radiation shielding was targeted as an addition to FDM materials. By creating a composite material using a thermoplastic polymer matrix and boron nitride additive, neutron shielding of FDM-printed samples was enhanced from 50% attenuation in polymer specimens to 72% in composite specimens. The enhanced functionality of this new material enables FDM technology to be used in the manufacture of aerospace components, where neutron radiation presents a significant hazard.

The phase stability, equilibrium lattice parameters, mechanical properties, and chemical bonding of M2B and M2B0.75C0.25 (M = Fe, Cr, W, Mo, Mn) were studied using first-principles calculations within density functional theory. These compounds are thermodynamic stability structures, and the M2B0.75C0.25 stability is worse than that of M2B. The equilibrium lattice parameters are consistent with other available experimental and theoretical data. Stress–strain and Voigt–Reuss–Hill approximations were used to estimate the elastic constants (Cij) and moduli (B, G, E), respectively. The bulk modulus and the ductility increased by adding an appropriate amount of C to the M2B. The compound hardness was studied using a theoretical method based on the work of Tian. The chemical bonding of these compounds was estimated using the Mulliken population analysis and density of states, and the results indicate that the bonding behaviors of these compounds are combinations of metallic and covalent bonds.

The hot deformation behavior of Ti–6Al–4V alloy with starting fully lamellar microstructure was investigated by conducting isothermal hot compression tests at the temperature of 700–1000 °C and strain rate of 0.001–10 s−1. The deformation activation energy is calculated to be 342 kJ/mol at temperatures from 750 to 850 °C, whereas the higher apparent activation energy of 610 kJ/mol is obtained at a high temperature regime of 900–1000 °C. The relationship between the dynamic softening behavior and deformation parameters was analyzed by power dissipation efficiency η, which shows an increasing trend as the deformation temperature increases and strain rate decreases, respectively. Processing maps were constructed. The instability flow is dominated by the presence of adiabatic shear bands, and the dynamic softening is mainly caused by a combination effect of dynamic recrystallization and dynamic recovery. Moreover, straining is found to have a positive effect on lowering the phase transformation temperature.

The microstructure evolution of the directionally solidified NiAl–Cr(Mo) planar eutectic lamellar structure was studied at 1150 °C and times of up to 400 h. The planar eutectic lamellar structure is obtained at the withdrawal rate range of 2.5–7.5 μm/s. The interlamellar spacing decreases gradually with increasing the withdrawal rate. The lamellar termination (like angular or smooth) commonly exists in the as-DS alloy. After high temperature treatment, the lamellar structure at 2.5 μm/s (interlamellar spacing, 3.7 μm) is almost stable, only a little migration of termination occurs at 400 h. When the withdrawal rate increases to 4.5 μm/s, the coarsening and migration of termination occur at 200 h. The adjacently coarsened terminations assemble when the coarsening processes to a certain degree, thus resulting in the formation of the blocky Cr(Mo) phase. Similarly, the above instable phenomenon occurs at 7.5 μm/s. The relevant instability mechanisms are discussed.

A Cu–3%Ti (wt%) alloy was processed by multiaxial forging (MAF) at cryogenic temperature up to 3 cycles, imposing a total strain of 1.6. Microstructure and mechanical properties of the unprocessed and cryo-forged samples were analyzed. X-ray diffraction results showed deviation in peak broadening and peak intensity of the cryo-forged samples in comparison to that of unprocessed, which are due to texture modification caused by grain refinement during the MAF process. Microstructural analysis showed reduction in grain size from 80 µm in the as-received condition to 250 nm after 3 cycles. Electron backscatter diffraction results indicated the transformation of high angle grain boundaries to low angle grain boundaries in all 3 cycles when compared to the as-received condition. Reduction in ductility was observed after 1 cycle, but with an increase in the number of cycles, both strength and ductility increased. After 3 cycles, ultimate tensile strength and hardness reached 1126 MPa and 427 Hv as compared to 528 MPa and 224 Hv for the as-received condition. Fractography analysis showed decrement in dimple size after 1 cycle, in comparison to that of the as-received condition. However, it kept on increasing for higher number of cycles.

Predictions of the mechanical response of polycrystalline metals and underlying microstructure evolution and deformation mechanisms are critically important for the manufacturing and design of metallic components, especially those made of new advanced metals that aim to outperform those in use today. In this review article, recent advancements in modeling deformation processing-microstructure evolution and in microstructure–property relationships of polycrystalline metals are covered. While some notable examples will use standard crystal plasticity models, such as self-consistent and Taylor-type models, the emphasis is placed on more advanced full-field models such as crystal plasticity finite elements and Green’s function-based models. These models allow for nonhomogeneity in the mechanical fields leading to greater insight and predictive capability at the mesoscale. Despite the strides made, it still remains a mesoscale modeling challenge to incorporate in the same model the role of influential microstructural features and the dynamics of underlying mechanisms. The article ends with recommendations for improvements in computational speed.

AlMg alloys have widespread industrial applications. Grain refinement techniques have been frequently used to achieve high strength in these alloys. Here, we report on the fabrication of epitaxial co-sputtered AlMg thin films with high-density growth twins. The microstructure evolution with varying Mg composition has been characterized. Nanoindentation and in-situ micropillar compression tests show that the strength of AlMg alloys increases with increasing Mg composition. The flow stress of epitaxial nanotwinned Al–10 at.% Mg thin film exceeds 800 MPa. The modified Hall–Petch plots incorporating the solid solution strengthening effect suggest that, compared to high angle grain boundaries, incoherent twin boundaries are equivalent barriers to the transmission of dislocations in nanotwinned AlMg alloys.

In fracture mechanics, established methods exist to model the stability of a crack tip or the kinetics of crack growth on both the atomic and the macroscopic scale. However, approaches to bridge the two scales still face the challenge in terms of directly converting the atomic forces at which bonds break into meaningful continuum mechanical failure stresses. Here we use two atomistic methods to investigate cleavage fracture of brittle materials: (i) we analyze the forces in front of a sharp crack and (ii) we study the bond breaking process during rigid body separation of half crystals without elastic relaxation. The comparison demonstrates the ability of the latter scheme, which is often used in ab initio density functional theory calculations, to model the bonding situation at a crack tip. Furthermore, we confirm the applicability of linear elastic fracture mechanics in the nanometer range close to crack tips in brittle materials. Based on these observations, a fracture mechanics model is developed to scale the critical atomic forces for bond breaking into relevant continuum mechanical quantities in the form of an atomistically informed scale-sensitive traction separation law. Such failure criteria can then be applied to describe fracture processes on larger length scales, e.g., in cohesive zone models or extended finite element models.

The multiplication of dislocations determines the trajectories of microstructure evolution during plastic deformation. It has been recognized that the dislocation storage and the deformation-driven subgrain formation are correlated—the principle of similitude, where the dislocation density (ρi) scales self-similarly with the subgrain size (δ): $\delta \sqrt {{\rho _{\rm{i}}}}$ ∼ constant. Here, the robustness of this concept in Cu is probed utilizing large strain machining across a swathe of severe shear deformation conditions—strains in the range 1–10 and strain-rates 10–103/s. Deformation strain, strain-rate, and temperature characterizations are juxtaposed with electron microscopy, and dislocation densities are measured by quantification of broadening of X-ray diffraction peaks of crystallographic planes. We parameterize the variation of dislocation density as a function of strain and a rate parameter R, a function of strain-rate, temperature, and material constants. We confirm the preservation of similitude between dislocation density and the subgrain structure across orders-of-magnitude of thermomechanical conditions.

The electrochemical behavior of TiNi(1−x)Nbx (x = 0, 0.05, 0.1, 0.2) ternary intermetallic compounds synthesized by mechanical alloying was investigated and compared to that of binary TiNi. The structure of 20-h milled product with initial stoichiometric composition of TiNi0.95Nb0.05 was found to be amorphous/nanostructured. Upon cycling, this ternary milled product exhibited the highest discharge capacity (166.1 mA h/g) after 10 cycles and best cycle stability (∼91%) while those of the binary TiNi were 147 mA h/g and ∼83%, respectively; i.e., slight amount of Nb substitution (0.05 mol) for Ni in the TiNi not only increased discharge capacity and cycle stability but also enhanced the kinetics of hydrogen absorption/desorption through increasing the exchange current density and hydrogen diffusion coefficient. However, additional Nb content was found to have negative effect on electrochemical properties; this was related to the existence of Nb element in addition to the ternary amorphous/nanocrystalline structures.

Cobalt-doped ZnO (CZO) film nanocomposites have been deposited on Si(100) substrates by pulsed electron beam ablation from a single Co0.2Zn0.8O target. The films have been deposited at various electron beam repetition rates (1, 2, 4, and 8 Hz), under a background argon (Ar) pressure of ∼3 mtorr, an accelerating voltage of 16 kV, and a deposition temperature of 450 °C. The effect of beam frequency on the structural, chemical, and morphological properties of the films has been assessed. The findings reveal that film thickness, film roughness, and degree of crystallinity of the ZnO wurtzite structure increase with beam frequency, while globule size and density reach maximum and minimum values, respectively, as the beam frequency is increased. The pulse frequency does not appear to affect the average nanoparticulate size. X-ray photoelectron spectroscopy data support the co-existence of metallic cobalt (Co0), CoO, and Co2O3 in CZO films near the surface. Phase analysis by X-ray diffraction also confirms the presence of hexagonal close-packed metallic cobalt whose content in the films is practically unaffected by beam frequency.

In this work, corrosion-resistant fluoridated Ca–Mg–P composite coatings were prepared on magnesium alloys via a hydrothermal assisted sol–gel process. All these coatings derived from Coating Sols with different F− concentrations are composed of fluoridated hydroxyapatite, magnesium hydroxide, and dittmarite. When F− concentration of Coating Sol is 0.03 M, the coating exhibited uniform and dense surface, and its thickness reached 32 μm, thus possessing a high charge transfer resistance of 312 ± 12.69 kΩ cm2 in simulated body fluid (SBF). Immersion test in SBF showed that this coating could quickly induce the formation of the mineralized layer, implying relatively high bioactivity. After 49 days of immersion, the original composite coating and newly formed mineralized layer reached 60 μm in thickness, providing effective long-term protection for magnesium alloys. These attractive results indicate that this fluoridated Ca–Mg–P composite coating is a promising protective coating on biodegradable magnesium and magnesium alloy implants for orthopaedic applications.

The effect of Cu addition varied from 0 to 4 mass% on the corrosion resistance and electrochemical response in Ni–Co–Cr–Mo alloys was investigated using potentiodynamic polarization, electrochemical impedance spectroscopy, and Mott–Schottky analysis. Results indicate that the Ni–Co–Cr–Mo alloy with 2 mass% Cu exhibited the most superior corrosion resistance, and the presence of Cu greatly influenced the outer porous layer. The Ni–Co–Cr–Mo alloys’ corrosion resistance was not simply increasing with copper addition increasing from 0 to 4 mass%. The X-ray photoelectron spectroscopy etching analysis was also conducted to illustrate the fraction of Cu at various depths in the passive film, and the results reveal that a maximum limit on Cu content (appropriately 3.10 mass%) existed in the outermost surface in the present condition. Among the studied alloys, the Ni–Co–Cr–Mo–2%Cu alloy formed the thickest passive film with the lowest donor density.

A commercially pure titanium (CP-Ti) of grade 1 as a hard-to-deform material was processed successfully by ECAP processing up to four passes at room temperature via the core–sheath method using a die with an internal channel angle of 90°. The simulation and analytical calculations demonstrated that imposed back pressure on the core was increased at each pass due to strain hardening of sheath metal (AISI 1015 steel) during deformation which prevented damage accumulation and crack initiation at a high number of passes. The scanning electron microscopy and transmission electron microscopy observations of ECAP-processed Ti revealed a severely deformed microstructure which consisted of a high dislocation density and an average grain size of ∼250 nm. Mechanical properties of four-pass ECAP-processed CP-Ti showed a substantial enhancement of ultimate tensile strength up to 890 MPa associated with a reasonable elongation to failure of 15.3%.

The micro-nano rough structure promotes the formation of superhydrophobic surfaces, while the formation of superoleophobic surfaces requires the support of re-entrant structures. Electrochemical etching and boiling water treatment methods were used to process the superoleophobic surface in the Al–Mg alloy substrate. The differences between the potential of the aluminum and the magnesium promoted the formation of the surface microstructure under the current stimulation, and the surface was formed into dense nanoscale needle-like coating after boiling water treatment. Scanning electron microscopy, energy dispersive spectroscopy, and contact angle measurement were performed to characterize the morphological features, chemical composition, and surface wettability, respectively. The so-prepared superoleophobic surfaces showed high contact angles and small sliding angles for water, ethylene glycol, and hexadecane. In addition, surface topography, reaction mechanism, and experimental parameters were also studied.

The evolution of fatigue performance and surface mechanical properties of AISI 304 stainless steel induced by the electropulsing-assisted ultrasonic surface rolling process (EP-USRP) was systematically investigated by integrating instrumented indentation, scanning electron microscopy with electron backscatter diffraction, and transmission electron microscopy. The results indicate that higher hardness, greater strength, finer ultra-refined grains, and higher residual compressive stress are formed within the strengthened layer compared with the original ultrasonic surface rolling process (USRP). EP-USRP with the optimized experimental parameters can produce a higher average rotating bending fatigue strength for AISI 304 stainless steel than USRP. Anomalously and noteworthily, all fatigue specimens treated by EP-USRP showed an incomplete fracture, revealing a higher reservation of safety in practical engineering applications. The further modified structure strengthening and stress strengthening induced by EP-USRP are likely the primary intrinsic reasons for the observed phenomena. Furthermore, the influence mechanism of EP-USRP was discussed scrupulously.

Atomic mixing by replacement collision sequences and other cascade effects is well known to create chemical disorder in irradiated alloys. Most studies of irradiation-induced disordering have focused on ex situ analysis of irradiated samples; however, fast in situ techniques are necessary to measure disordering at elevated temperatures without significant interference from concurrent re-ordering processes. In the present work, we use in situ electron diffraction with high speed data collection to measure the initial change in the long-range order parameter S with ion dose ϕ during 500 keV Ne+ irradiation of Cu3Au foils. The data reveal an unexpected and dramatic increase in the disordering rate as the critical order–disorder transition temperature TC is approached. Molecular dynamics simulations show that this increase is not due to temperature-dependent cascade mixing. We attribute the enhanced disordering, instead, to coupling between point defect fluxes and the chemical state of order.

We suggest a new method to evaluate stress directionality, the ratio of principal stresses, using nanoindentation by introducing a modified Berkovich indenter that is extended in one direction from the Berkovich indenter. In a nonequibiaxial stress state, the indentation load-depth curves are shifted differently as the extended axis of the indenter is placed in accordance with each principal direction. The indentation load-difference is proportional to each principal stress and the slopes are defined by the normal and parallel conversion factors whose ratio is constant at 0.58. The suggested method was verified by indentation tests using five nonequibiaxial stressed specimens. The evaluated stress directionality results show agreement with the applied reference values within ±20%. Furthermore, we calculated the conversion factor ratios for other modified Berkovich indenters extended to different degrees through finite element analysis and confirmed that the conversion factor ratio was inversely proportional to the extension of the modified Berkovich indenter.

Given the global water challenges, solar-driven steam generation has become a renewed topic recently as an energy-efficient way for clean water production. Here, a hybrid plasmonic structure consisting of a top layer of TiN nanoparticles (NPs) and a bottom layer of mesoporous anodized alumina membrane (AAM) was rationally designed and fabricated. The top TiN NPs with broadband light absorption acted as a plasmonic heating layer, which converted the absorbed light to heat efficiently for interfacial water heating. The AAM acted as the mechanical support layer, guaranteeing the heat isolation and continuous water replenishment. With optimized thickness of the TiN top layer, a solar steam generation efficiency of 87.7% was achieved in this study. This efficiency is comparable or even higher than prior studies. The current work proves the capability of the TiN NPs as an alternative photothermal material.

In this study, varying contents of ultrafine bamboo-char (UFBC) were introduced into PLA/bamboo particle (BP) biocomposites as new reinforcements to improve the mechanical, thermal, and morphological properties of the biocomposites. The new strategy was aiming to realize the synergistic effects of reinforcement and toughening of poly(lactic acid) (PLA) composites through a simple method without surface modification and other additives. The maximum tensile strength, modulus, and elongation at break of 45.20 MPa, 540.50 MPa, and 7.53% were reached at 5.0 wt% UFBC content, which were slightly lower than those of pure PLA. The maximum modulus of elasticity of the ternary biocomposites was 5316.1 MPa at 5.0 wt% UFBC content, which was approximately 2 times higher than the pure PLA. Impact strength reached a maximum value of 38.56 J/m when the UFBC content was 5 wt%, and improved by 376% compared with pure PLA of 7.88 J/m. Meanwhile, compared with the PLA/BP binary composite of 20.50 J/m, it improved 88%. A concrete-like microstructure system was achieved (i.e., cement, sand, and rebar corresponding to PLA, UFBC, and BP, respectively).