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Nanocrystalline multi-main-phase (MMP) Nd-Ce-Fe-B magnet can effectively suppress the magnetic dilution effect of Ce. However, its low coercivity and poor thermal stability have not been adequately overcome. In this work, a novel low-melting-point Gd 60 Y 10 Cu 15 Al 15 alloy was introduced into MMP Nd-Ce-Fe-B magnet through intergranular addition for simultaneously enhancing its coercivity and thermal stability. The results show that the intrinsic coercivity H cj is obviously improved, and its maximum increment is ∼12.3 % at 4 wt% Gd 60 Y 10 Cu 15 Al 15 alloy. Especially, the increase in H cj is more significant, and an abnormally increase in the maximum energy product (BH) max occurs at high temperature of 150 °C. Meanwhile, the reversible temperature coefficients of H cj (β) and B r (α) are improved simultaneously. These findings imply the enhanced thermal stability for the MMP magnet with Gd 60 Y 10 Cu 15 Al 15 addition. The microstructural characterizations, compositional analyses and micromagnetic simulations reveal that the competitive effects of the formed non-ferromagnetic grain boundary (GB) phase and Y or Gd diffusion into the main phase lead mainly to a synergistic improvement in the coercivity and thermal stability of the magnet. This work is expected to provide a promising cost-effective approach for developing the high-performance thermally-stable Nd-Ce-Fe-B magnet and explore more possibilities for effective utilization of Y or Gd rare-earth resources. • The Research Highlights in this paper are as follows: • A novel low-melting-point Y-Gd based alloy was developed and used to modify the nanocrystalline MMP Nd-Ce-Fe-B magnet. • H cj and thermal stability of nanocrystalline MMP magnet are synergistically enhanced. • Microstructure evolutions and composition distributions are revealed. • The enhanced mechanisms for H cj and thermal stability are systematically analyzed. [ABSTRACT FROM AUTHOR]

This paper aims to improve the magnetic properties of sintered Nd Fe B magnet. Ni powders were added to the Nd Fe B magnet through intergranular addition, and their effects on the microstructure and magnetic properties of the magnet were investigated. By adding a proper amount of Ni (0.3 wt%), the intrinsic coercivity H cj of Nd Fe B magnet is significantly improved with only a slight decrease in the remanence B r and the maximum energy product ( BH ) max . The microstructural and compositional analyses reveal that Ni atoms not only enter the matrix phase but also concentrate in the intergranular regions either as Ni-containing Nd-rich phase or as Ni particles. This is consistent with the thermodynamic calculation results. Furthermore, a sintering mechanism of magnet with intergranular addition of Ni powders is tentatively proposed. These results may provide a reference for improving the magnetic properties of sintered Nd Fe B magnets. [ABSTRACT FROM AUTHOR]

The microstructure and chemical heterogeneity play critical roles in the magnetic performance of nanocrystalline multi-main-phase (MMP) Nd–Ce–Fe–B magnets. In this work, we report a strategy to synergistically tailor the microstructure and chemical heterogeneity of MMP magnet through optimizing sintering temperature (T s). An optimum T s of 700 °C has been obtained for nanocrystalline MMP Nd–Ce–Fe–B magnets. When sintered at T s = 700 °C, the nanocrystalline MMP magnet exhibits the maximum intrinsic coercivity H cj , the preferable remanence B r , and the resultant optimum maximum energy product (BH) max , which is attributed mainly to the appreciable density, controlled grain size, and better chemical heterogeneity. Comparably, lower or higher T s leads to the inferior magnetic properties. At lower T s below 700 °C, the poor magnetic properties are mainly due to the insufficient densification. However, at higher T s above 700 °C, the decreased H cj originates mainly from the excessive grain growth and gradual chemical homogenization. The above findings deepen our understanding on the relationship among the microstructure, chemical heterogeneity, and T s , concurrently providing an effective approach for fabricating low-cost high-performance nanocrystalline MMP Nd–Ce–Fe–B magnets. • Microstructure and chemical heterogeneity of nanocrystalline MMP Nd–Ce–Fe–B magnet are synergistically tailored. • H cj , B r , and (BH) max are simultaneously enhanced at optimum T s of 700 °C. • Dependences of microstructure and composition on T s are revealed, and an evolution model is proposed. • Mechanisms underlying changes in magnetic properties with T s are systematically analyzed. [ABSTRACT FROM AUTHOR]

• Thermally-stable high-performance nanocrystalline MMP Nd-Ce-Fe-B magnet is fabricated by grain boundary engineering. • H cj and thermal stability are obviously improved with simultaneously enhanced (BH) max. • Microstructure evolution is revealed, and the Dy diffusion model is proposed. • The underlying mechanisms for enhanced magnetic properties and thermal stability are systematically analyzed. Low coercivity and poor thermal stability are still the main challenges for practical application of low-cost Nd-Ce-Fe-B magnet. To solve these challenging problems, a strategy to simultaneously improve the coercivity and thermal stability of Nd-Ce-Fe-B magnet through combining the nanocrystalline multi-main-phase (MMP) structure and grain boundary engineering is demonstrated. In this study, nanocrystalline MMP Nd-Ce-Fe-B magnet was grain boundary engineered by co-adding DyF 3 and Cu powders. The results show that the intrinsic coercivity H cj is significantly improved, and meanwhile optimum maximum energy product (BH) max is achieved at 2 wt% DyF 3 -Cu. Moreover, the superior reversible temperature coefficients of H cj (β) and B r (α) are both achieved, implying the improved thermal stability for the DyF 3 -Cu added magnet. Microstructural and compositional characterizations indicate that the modified RE-rich phase, the inhibited abnormal grain growth near the flake boundary, and the diffused Dy towards main phase grains are the main reasons for simultaneously enhanced magnetic properties and thermal stability. Thus, combining the nanocrystalline MMP structure and grain boundary engineering will be a promising approach for preparing thermally-stable high-performance Nd-Ce-Fe-B magnet. [ABSTRACT FROM AUTHOR]

Sintered Nd–Fe–B magnets with and without Dy 2 O 3 were prepared by powder blending method. The temperature-dependent magnetic properties, thermal stability, microstructure and corrosion resistance of sintered magnets were investigated. The temperature-dependent magnetic properties revealed that with intergranular addition of Dy 2 O 3 , the reversible temperature coefficients β and α in the range of 293–373 K were both lowered, indicating that the thermal stability was effectively improved. This was also verified by the decreased irreversible flux loss ( h irr ) and the increased maximum operating temperature (MOT). Moreover, the electrochemical and accelerated corrosion results clearly evidenced that the corrosion resistance of Nd–Fe–B magnet was also modified by addition of Dy 2 O 3 . Furthermore, the related mechanisms on improved thermal stability and corrosion resistance were systematically discussed. [ABSTRACT FROM AUTHOR]

Highlights: [•] Oxidation phenomenon in one laser spot on stainless steel surface is studied. [•] Compositions and morphologies vary from center to edge in one laser spot. [•] Hexagonal Cr2O3 distributes in the edge, while spherical Fe2O3 in the center. [•] Oxidation mechanism is proposed based on thermodynamics and kinetics. [Copyright &y& Elsevier]

Abstract: The butt welding of 304 stainless steel plates with thickness of 3mm and 6mm were achieved by YLR-6000 fiber laser under Ar protective gas. The weld appearance, microstructure, composition distribution and microhardness of welded joint were emphatically investigated. The results showed that the narrow and fully penetrated welded joint without marco-defects can be obtained with tightly focused 2kW fiber laser power and 20mm/s welding speed. The weld bead was smooth, and various microstructures typically formed at different zones of the welded joint. The fine columnar and equiaxed crystals existed in the edge and center of weld bead, respectively. Both were different with the microstructure of the stainless steel substrate. However, the composition distribution of the welded joint had no obvious changes. Furthermore, the superior microhardness of welded joint over the stainless steel substrate was mainly attributed to its finer microstructure. [Copyright &y& Elsevier]

Abstract: Sintered Nd–Fe–B magnets with various degrees of grain alignment are prepared by the conventional powder metallurgy technique. The magnetic properties, bending strength and fracture morphologies of sintered magnets with different alignment degrees are investigated. The results show that the remanence B r and maximum energy product (BH)max increase, while intrinsic coercivity H cj decreases gradually with increasing the alignment degree. Moreover, the bending strengths measured by applying force parallel (σ bb∥) and perpendicular (σ bb⊥) to the alignment magnetic field H appl present opposite variation tendency, and σ bb∥ is larger than σ bb⊥, suggesting the more significant anisotropy of mechanical properties with increasing the degree of grain alignment. Furthermore, the related mechanisms are systematically analyzed. [Copyright &y& Elsevier]

Abstract: Different surface morphologies on AISI 304 stainless steel have been obtained after millisecond Nd:YAG pulsed laser oxidation. The effects of laser processing parameters, especially pulse width and laser energy density on the surface morphologies of the stainless steel were emphatically investigated. The results showed that surface morphologies were significantly changed with increasing laser pulse widths and laser energy densities. When the pulse width was 0.2–1.0ms and laser energy density was 4.30×106–7.00×106 J/m2, the surface was obviously damaged and the morphologies varied gradually from craters to ripple structures. However, when the pulse width was longer than 1ms and the laser energy density was increased from 1.90×107 to 3.16×107 J/m2, the sizes of craters got smaller until disappeared and the surface became flatter and smoother. Nevertheless, the smooth surface was not obtained under overhigh laser energy densities. In addition, the schematic relationship was used to describe the formation process and mechanism of different surface morphologies. [Copyright &y& Elsevier]

Abstract: Different laser energy densities were utilized to treat AISI 304 stainless steel via Nd:YAG pulsed laser surface melting (LSM). The surface composition and microstructure of the stainless steel were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and field emission scanning electron microscopy (FESEM). In particular, the corrosion behaviors of the stainless steel surface without and with LSM were evaluated by the electrochemical polarization measurement in 3.5wt.% NaCl aqueous solution at room temperature. The results showed that the stainless steel surface without LSM suffered severe localized pitting under the testing conditions. A thin surface oxide protective layer was produced on the stainless steel surface with LSM, which considerably improved the corrosion resistance properties of the stainless steel. The height differences of the corrosion regions on the stainless steel surface with LSM were measured to establish more corrosion resistant region, using scanning confocal laser microscopy. The underlying corrosion mechanism of the stainless steel with LSM was revealed. [Copyright &y& Elsevier]

Abstract: The present study concerns the simulation and analysis of the flow field in the upper human respiratory system in order to gain an improved understanding of the complex flow field with respect to the process affecting drug delivery for medical treatment of the human air system. For this purpose, large eddy simulation (LES) is chosen because of its powerful performance in the transitional range of laminar and turbulent flow fields. The average gas velocity in a constricted tube is compared with experimental data () and numerical data from Reynolds-averaged Navier–Stokes (RANS) equations coupled with low Reynolds number (LRN) κ–ω model () and LRN shear–stress transport κ–ω model (), for model validation. The present study emphasizes on the instantaneous flow field, where the simulations capture different scales of secondary vortices in different flow zones including recirculation zones, the laryngeal jet zone, the mixing zone, and the wall shear layer. It is observed that the laryngeal jet tail breaks up, and the unsteady motion of laryngeal jet is coupled with the unsteady distribution of secondary vortices in the jet boundary. The present results show that it is essential to study the unsteady flow field since it strongly affects the particle flow in the human upper respiratory system associated with drug delivery for medical treatment. [Copyright &y& Elsevier]

Abstract: ZnO nanoporous films consisting nanocrystals on ITO-coated glass substrates were prolongedly electrodeposited under pulse voltages in zinc nitrate solution at room temperature. Their structures were found to be determined by experimental parameters, especially, the voltage and the deposition time. On the basis of the structural characterization, the growth mechanism was proposed as a combined growth process: the competitive growth between lateral overgrowth and nanovoid formation. The structural evolvement is believed to be due to the decrease of surface potential with deposition time, leading to the formation of a quasi-two-layer structure. The revealed mechanism here could be helpful to understand the growth and corresponding properties of ZnO films as well as their nanostructures. [Copyright &y& Elsevier]

Abstract: Experiments were conducted to study the microstructure and tensile properties of the sub-micro and nano-structured Al produced by the Nd:YAG pulsed laser surface melting (LSM). The surface and longitudinal section microstructures of the Al samples after LSM were analyzed. The solidification microstructures in the LSM region were very fine which was beneficial to improve the properties of the Al sample. The tensile behavior and the relevant fracture mechanism of the LSM layer on the Al surface were investigated based on the analyses of the tensile test results. The fracture morphologies in the LSM region were small and shallow dimples with the size of 0.4–1μm. It indicated that the Al sample showed the ductile behavior because the grains were refined effectively after LSM. Furthermore, the typical amorphous fracture morphology with the fish scale structure was also obtained at the strain rate of 1.0×10−4 s−1 after LSM with the laser power density of 3.65×109 W/m2. [ABSTRACT FROM AUTHOR]

Abstract: The laser surface melting (LSM) technique was adopted to modify the surface layer microstructure of the AISI 304 stainless steel in this paper. The results showed that the hexagonal morphologies have been successfully fabricated on the surface after LSM. These hexagons had side lengths of about 0.5–1μm and were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), field emission scanning electron microscope (FESEM) and high resolution transmission electron microscope (HRTEM). It was proved by the XRD that the stainless steel surface mainly consisted of γ-Fe, Cr2O3, Fe2O3 and some manganese oxides. The FESEM micrographs showed that the hexagonal oxides were regular hexagons in geometry. The HRTEM micrographs also indicated the presence of the hexagons on the surface of the stainless steel. The spacing values were calculated from the HRTEM micrograph and the SAED pattern, and the hexagonal oxide phases determined by these spacing values were consistent with those verified by the XRD. After LSM, the microhardness of the stainless steel was significantly improved. [Copyright &y& Elsevier]

Abstract: We have grown Fe3N films on GaN(0002) substrates by metalorganic chemical vapor deposition (MOCVD). Under lower growth temperatures, small iron particles were formed on GaN surface, while under higher growth temperatures, Fe3N films were formed. The surface morphology of samples with different growth temperatures were characterized by atomic force microscopy. In X-ray Photoelectron Spectroscopy (XPS) measurement, the coexistence of metallic Fe and Fe2+ or Fe3+ was observed in the sample grown at 600°C, while the sample grown at 1050°C showed only high valence forms of Fe ions. It was also found that the magnetic moments of Fe3N prefer to align normal to the c-axis. [Copyright &y& Elsevier]

Abstract: To improve the magnetic properties and corrosion resistance of magnet, SiO2 nanopowders were added into Nd28.25Dy2.75FebalAl0.15Ga0.1Nb0.1B0.98-sintered magnets as grain boundary modifiers. It was found that the intrinsic coercivity (H cj), remanence (B r) and corrosion resistance were all improved with addition of certain amount of SiO2 nanopowders. The optimum addition amount of SiO2 nanopowders was found to be 0.01wt%. Thermodynamic calculation in combination of energy dispersive X-ray spectroscopy (EDX) analyses indicated that SiO2 nanopowders reacted with Nd of Nd-rich phase. As a result, the intergranular phase was modified, and the grain growth of main phase was restrained. It led to the optimization of microstructure. [Copyright &y& Elsevier]

Abstract: Sintered permanent magnets have been prepared by blending Nd–Fe–B jet-milled powders with Cu nanopowders (0, 0.05, 0.1 and 0.2wt%) before pressing in a perpendicular magnetic field. Permanent magnetic properties, Curie temperature (T c), microstructures and corrosion resistance of the sintered magnets were investigated. Microstructural characterization revealed that the grain size of Nd2Fe14B phase was refined and more homogeneous, and the grain boundaries became clear and smooth by the addition of Cu nanopowders, resulting in the improvement of coercivity H c j . Moreover, the corrosion resistance of Nd–Fe–B magnets was also improved. However, T c remained nearly unchanged with Cu addition, which was consistent with the elemental analysis results. Cu was not detected in the matrix phase Nd2Fe14B, but concentrated in the intergranular region. [Copyright &y& Elsevier]

• Cuttlebone-inspired honeycomb with asymmetric sinusoidal walls is first proposed. • Effect of the wall amplitude and gradience on the crushing performances are revealed. • The mechanism of honeycomb is fully studied through FEM and the elastic theory. Inspired by cuttlebone microstructure, this study proposes a novel bionic square-tube cuttlebone-inspired honeycomb (S-CIH) structure prepared by digital light processing (DLP) method. Fifteen configurations of honeycombs of same mass including S-CIH, regular honeycomb (S-RH) and sinusoidal honeycomb (S-SH) structures are evaluated and compared in terms of the deformation behavior and compressive performances under out-of-plane compression, especially energy-absorbing capacity. The results indicate that the S-CIH structure achieves the improved energy absorption 8.859 J/g, over 40 % and 60 % than that of S-RH and S-SH structure with same relative density and mass, respectively. The mechanism analysis of the asymmetric corrugated walls disposed in cross and parallel in S-CIH, reveals that the magnitude of amplitude determines the buckling mode thus folding mode of walls, and the magnitude of amplitude gradient determines whether the whole honeycomb structure can achieve a progressive failure. Optimal structural ratio can enable S-CIH delay the complete failure and improve the long-term failure-resistance. This indicates that S-CIH design has the potential ability to strengthen and toughen other brittle matrix materials, and the cuttlebone-like architecture provides a new biological design of mechanically efficient meta-honeycomb beyond conventional honeycomb structure. [Display omitted] [ABSTRACT FROM AUTHOR]

Nanostructured multi-main-phase (MMP) Nd-Ce-Fe-B magnet produced by melt-spinning powders has great potential for achieving high performance. However, the inferior intrinsic properties of the Ce 2 Fe 14 B phase lead to the low coercivity and thermal stability of this magnet. In this study, low-melting-point Pr 68 Cu 32 powders were introduced into nanostructured MMP magnet through intergranular addition to further improve its coercivity and thermal stability. When only 2 wt% Pr 68 Cu 32 was added, the intrinsic coercivity H cj and thermal stability were significantly improved with a slight reduction in the remanence B r and the maximum energy product (BH) max. The microstructure evolution of MMP magnet with adding Pr 68 Cu 32 was revealed by microstructural and compositional characterization and thermodynamic calculation, and a schematic model was proposed. Furthermore, mechanisms underlying changes in magnetic properties were systematically analyzed by combining micromagnetic simulation. ● Grain boundary modification is adopted for fabricating high-performance nanostructured MMP Nd-Ce-Fe-B magnet. ● H cj and thermal stability are significantly improved with a slight reduction in B r and (BH) max. ● Microstructure and microchemistry evolution are investigated and a corresponding model is proposed. ● Mechanisms underlying changes in magnetic properties are systematically analyzed. [ABSTRACT FROM AUTHOR]

Novel morphologies of chromium sesquioxide (Cr 2 O 3 ) were successfully formed on AISI 304 stainless steel surface by Nd: YAG pulsed laser oxidation in air. The obtained Cr 2 O 3 presented mainly dendritic, gear-like, flower-like and regular hexagonal morphologies with sizes from hundred nanometers to several micrometers. These various morphologies chiefly originated from two groups of diverse growth directions within (0 0 0 1) basal plane, i.e., 〈 2 1 ¯ 1 ¯ 0 〉 and 〈 0 1 1 ¯ 0 〉 directions. The preferential growth along different directions determined the final Cr 2 O 3 morphologies. And the crystallographic analyses basically accorded with the experimental results. Moreover, the growth mechanism of the hexagonal Cr 2 O 3 was analyzed in detail from its morphology evolution, and a corresponding growth model was reasonably proposed. [ABSTRACT FROM AUTHOR]

• A novel bio-inspired self-similar nesting (SN) strategy is applied to basic truss units. • The optimal nesting ratio lead to dual-plateaus and improved energy-absorption. • SN strategy has the potential to be applicable to various strut-based units. Inspired by natural self-similar nesting (SN) strategy, the basic truss unit simple cubic (SC), face centered cubic (FCC), and body centered cubic (BCC) were regenerated into novel architected SN units, aiming to achieve dual-plateaus and improved energy-absorbing capacity compared to basic truss units. Through compression experiments, finite element analysis, microstructure observation and theoretical calculation, the SN lattices were investigated to explore the influence of the nesting ratio on the compressive responses. The optimal nesting ratio was verified as 0.4 for the unit size of 8 mm and the relative density of 20%, enable SN-SC and SN-FCC achieve the stable and excellent energy absorption capabilities. Furthermore, the underlying mechanism of dual-plateau achieved by SN strategy was revealed that a SN unit can be zoned into a stronger region containing the nested core SC/FCC and a weaker region consisting of exterior nest SC/FCC and mediation BCC. The higher yield strength of the nested core SC/FCC compared to the exterior nest SC/FCC and BCC actually cause the second higher stress plateau and the better failure-resistance for the SN lattices. The improvement effect of SN strategy on SC and FCC units indicates that SN strategy has the potential to be applicable to various strut-based units. [Display omitted] [ABSTRACT FROM AUTHOR]

Lightweight refractory high-entropy alloy coatings (RHEAcs) of Nb x Mo 0.5 Ti 1.5 Ta 0.2 Cr (where x = 1, 1.3, 1.5, and 2) were fabricated on the surface of 316L stainless steel using pre-placed powder laser cladding (LC) technology. A comprehensive study was conducted to elucidate the effect of Nb content on the microstructure, microhardness and wear resistance of Nb x Mo 0.5 Ti 1.5 Ta 0.2 Cr RHEAcs before and after annealing at 900 °C for 10 h. The results show that the grains are gradually refined with the increase of Nb content. The coating consists mainly of a body-centered cubic (BCC) solid solution, C15-Laves phase, and a small amount of hexagonal close-packed (HCP) solid solution containing Ti. The microhardness of RHEAcs is significantly higher compared to the base material. Notably, at Nb 1.3 , due to the possibility of dislocation, the microhardness reaches a peak of 1066.5 HV, which is about 7.11 times higher than that of the base material. On the contrary, at Nb 2 , the microhardness is at its lowest point, averaging 709.31 HV, but 4.72 times that of the base material. After annealing, an increase in microhardness is observed at all Nb concentrations, up to 31.2% at Nb 2. Before annealing, the wear resistance of RHEAcs was slightly better than that of 316L stainless steel at different Nb contents. However, after annealing, the coefficient of friction (COF) and wear rate of the coatings are lower than those of annealed 316L stainless steel, highlighting their excellent wear resistance. It is noteworthy that the loss of wear properties after annealing at Nb1 is at a minimum, obtaining the most balanced wear resistance before and after annealing. The enhanced wear resistance after annealing can be attributed to the presence of ultra-fine grain oxide friction layers, mainly composed of TiO 2 and Ta 2 O 5. The main mode of wear is oxidative wear, with a small amount of wear from abrasive wear. • Compositional design of a new non-equimolar-ratio lightweight refractory high-entropy alloy. • Preparation of high-performance coatings by laser cladding technology and careful analysis of the micro-morphology and elemental distribution of the coatings. • Comprehensive testing of coating microhardness, abrasion resistance, and mechanical properties after annealing. [ABSTRACT FROM AUTHOR]

• Double truncated tetrahedral tensegrity (DTTT) structure is firstly introduced. • DTTT exhibits superior energy absorption compared to traditional truss lattices. • DTTT with relative density of 12% displays the optimal mechanical performances. In this paper, we studied a double truncated tetrahedron tensegrity (DTTT) structure. A experiment and simulation investigation were made to explore the compressibility of DTTT structure. Firstly, the relative density of the structure is controlled by the thickness of the bar, and to control the relative density to explore its impact on structural compression performance. The results show that DTTT structure has the best compression performance when the relative density is 12%. Under these conditions, FCC and Kelvin structures are introduced as contrast groups. The results show that DTTT structure exhibits excellent energy absorption performance, average crushing force performance and crushing force efficiency performance, and the crushing efficiency performance is higher than 36% of FCC, more than 42% of Kelvin. [ABSTRACT FROM AUTHOR]

Abstract: To improve the corrosion resistance and magnetic properties, Al85Cu15 (at.%) compound powders were added to (Pr, Nd)14.8Fe78.7B6.5 sintered magnets as grain boundary modifiers. The corrosion resistance was found to be remarkably improved by small additions of Al85Cu15 powders. When 1.2wt% Al85Cu15 was added, the corrosion rate of magnets in humid environments was reduced by two orders of magnitude. This is partly due to the stability enhancement of the (Pr, Nd)-rich intergranular phase by Cu and Al. In addition, the occurrence of the Cu-rich phase ((Pr, Nd)22Fe56Cu10Al2O10), whose open-circuit potential is higher than the (Pr, Nd)-rich intergranular phase, may be another reason for the improvement of the corrosion resistance. Furthermore, the magnetic properties of (Pr, Nd)14.8Fe78.7B6.5 were also improved by adding 0.3–1.2wt% Al85Cu15. Optimum addition amount was 0.6wt%. The improvement of the magnetic properties may be related to the microstructural modification and the increase of magnet density. [Copyright &y& Elsevier]

Microstructural evolution and mechanical properties of an aging 6061 Al alloy subjected to laser shock processing treatment (post-aging LSP treatment) were investigated by transmission electron microscopy (TEM) and mechanical tests. Results showed that the precipitates formed during aging treatment still remained, and the grain was refined by the ultra-high plastic strain plastic deformation during subsequent LSP treatment. Moreover, the precipitates effectively interacted with the dislocations induced by LSP. These typical microstructures contributed to the improvement in mechanical properties of the Al alloy. Relatively higher microhardness and strength were observed for the post-aging LSP Al sample. Furthermore, the synergistic strengthening mechanism involving the interaction of precipitate with dislocation, dislocations, and refined grains were clearly revealed. • The Research Highlights in this paper are as follows: • Novel process combining aging and LSP, i.e., post-aging LSP treatment, is reported. • Grain refinement, interaction between dislocation and precipitate, are discussed. • Synergistic strengthening mechanisms during post-aging LSP treatment are revealed. [ABSTRACT FROM AUTHOR]

• Novel bionic cuttlebone-like metallic sandwich structure is proposed and studied. • Cuttlebone-like sandwich shows exceptionally enhanced strength and toughness. • Parametric investigation reveals optimal design strategy for crushing performance. • Collapse modes affected by dimension parameters dominate the energy absorption. Inspired by cuttlebone, this study proposes a bioinspired metallic sandwich structure with matrix material of Ti-6Al-4V prepared by selective laser melting method. The bioinspired cuttlebone-like sandwich (CLS) structure is evaluated in terms of compression resistance and energy-absorbing capacity, thereby examining the influential dimensional parameters and the underlying collapse mechanisms of the core of CLS structure which are asymmetrical corrugated walls. Then, Parametric investigation of CLS structure demonstrates that the amplitude of the asymmetrical corrugated walls plays a significant role in the compression performance compared with other structural parameters. Besides, the collapse analysis of the corrugated walls revealed that the local buckling around Y-direction followed by progressive folding is expected for high energy absorption. And the optimal design strategy for the CLS core is summarized. Moreover, bionic CLS structure is confirmed with high strength and great energy dissipation by experiment and simulation methods, and is validated superior to other typical sandwich structures. This CLS metallic structure shows the potential of applying in protective energy-absorbing components in aerospace, armament and medical industry. And this study can be conducive to the development of novel energy-absorbing structural metallic materials. [Display omitted] [ABSTRACT FROM AUTHOR]

Bionic design is an effective strategy for obtaining lightweight, high-performance, and even multifunctional structures. Here, we found a novel hierarchical lamellar chamber microstructure in cuttlebone. To determine whether and how this cuttlebone-like hierarchical structure (CL-H) works on its mechanical properties, various lattices with CL-H cellular structure through digital light processing technique were designed and fabricated. Results showed that the CL-H lattice had excellent mechanical performances, achieving specific energy absorption up to a dozen times that of the non-hierarchical cuttlebone-like structure (CL) and triply periodic minimal surface structures. The CL-H lattices presented progressive failure behaviors depending on the numbers of sub-chambers. Furthermore, the mechanisms of energy absorption characteristic and failure behavior were systematically analyzed by combining microstructure examination and FEM simulation, and a schematic model was proposed. This study shed light on the design and engineering of advanced bio-inspired materials with excellent mechanical properties. • Novel cuttlebone-inspired multi-hierarchical bionic structure is analyzed. • Various lattices with cuttlebone-like structures through DLP are discussed. • Mechanisms of energy absorption characteristic and failure behavior are revealed. [ABSTRACT FROM AUTHOR]

A facile approach to fabricate a surface nanocomposite structure by embedding SiC nano-particles (NPs) via laser micro-melting is reported. A high fidelity model is adopted to reveal transient temperature distributions and the embedding of the SiC NPs into an Al molten pool during laser micro-melting. Special attention is paid to the embedding dynamic behaviours within the molten pool affected by Marangoni convection. Fluid flow and migration characteristics of the SiC NPs into the molten pool, as well as the resultant bubble motion and pore defects formation, are considered. Simulation results show that the temperature distribution is basically symmetrical with respect to the laser beam, and the Marangoni convection in the molten pool tends to embed the SiC NPs into the Al surface layer together with gas bubbles. This phenomneon is well validated by the experimental study on the surface morphology and the SiC NPs distribution in the Al surface layer. Microstructural characterizations indicate that a relatively flat reinforced SiC/Al surface can be formed at an optimized laser energy of 0.6 J. These studies may provide a new strategy for constructing nanocomposite structure on metal alloy surface. [ABSTRACT FROM AUTHOR]

We evaluated the electrochemical performances of LaNi 0.6 Fe 0.4 O 3 (LNFO) and LaNi 0.6 Co 0.4 O 3 (LNCO) perovskites as cathodes in La 0.8 Sr 0.2 Ga 0.83 Mg 0.17 O 2.815 (LSGM) electrolyte-supported solid oxide fuel cell. Both samples show excellent chemical compatibility with the LSGM electrolyte up to 900 °C, and exhibit small-polaron type electrical conduction with a high conductivity σ ≈ 510 (430) S·cm −1 at 800 °C and a small activation energy E a e = 54.9 (44.4) meV for LNFO (LNCO). The oxygen-reduction reaction evaluated in a symmetric LNFO(LNCO)|LSGM|LNFO(LNCO) cell gives a polarization resistance R p ≈ 0.51 (0.34) Ω·cm 2 at 800 °C in air and an activation energy E a O = 1.61 (1.87) eV. For a single cell composed of LNFO (LNCO) cathode, 300-μm-thick LSGM electrolyte, and a composite Ni + Gd-doped ceria anode, the maximum power densities reach P max = 490 (650) and 850 (1015) mW·cm −2 at 800 and 850 °C, respectively. These results demonstrated that LNFO and LNCO are promising cathode materials for the IT-SOFCs. [ABSTRACT FROM AUTHOR]

• Deformation behaviors and damaging mechanisms of foam structures printed by TPP were reported. • Large strain responses were analyzed through micro-compression and micro-bending experiments. • Foam structures were deformation-recoverable and can enable hierarchical crack buffering. Low-density polymer 3D foam structures are essential for aerospace structures, lightweight vehicles, and energy absorption due to their excellent mechanical properties. Up to now, it is still a challenge to achieve efficient and high-quality preparation of foam structure. Two-photon polymerization (TPP), is regarded as one of the most promising methods due to its unique combination of true 3D fabrication capability and high spatial resolution. The key to the wide application of the TPP foam structures depends on their mechanical performance and micro-architectural stability. Here, taking the woodpile foam structure as the research object, the large strain loading responses have been analyzed through micro-compression and micro-bending experiments. Especially the microstructures and deformation behavior of the woodpile foam are investigated in order to reveal the deformation-recoverable and micro-crack buffering deformation behavior, as well as the damaging mechanism. The structures of the foam before and after deformation are examined using optical microscopy (OM) and coherent anti-Stokes Raman scattering (CARS) microscopy. Experimental results demonstrate that such structure is deformation-recoverable and can enable hierarchical crack buffering, which slows the propagation and growth of multiple micro-cracks and maintains the good performances of the foam. It reflects the real reliability relationship of structure and performance suffering to loadings. [ABSTRACT FROM AUTHOR]

Abstract: The effects of laser shock processing (LSP) on tensile property of LY2 aluminum (Al) alloy were investigated, and strain rate sensitivity of the untreated and treated samples by LSP was studied at the strain rates ranging from 0.00001s−1 to 0.1s−1. In both conditions, fracture morphologies were observed by field emission scanning electron microscope (FESEM), and the microstructure in the near-surface region was characterized by transmission electron microscopy (TEM), respectively. Experimental results showed that LSP can obviously improve the ultimate tensile stress and elongation of LY2 Al alloy, and the strain rate sensitivity of the treated sample appeared to be remarkable. The improvement of tensile properties may be explained by the fact that the grain in the LSP-shocked region was obviously refined. Dynamic strain aging was found in the treated sample at the strain rate ranging from 0.00001s−1 to 0.0001s−1, and the underlying formation mechanism was revealed. [Copyright &y& Elsevier]

Abstract: Effects of the cooling rate of strip cast ingots on magnetic properties of sintered NdFeB magnets were studied. It is found that the magnetic properties greatly depend on wheel speed due to different alloy microstructures, which affect readily the particle size distribution of powders obtained after the subsequent jet milling. At higher cooling rate, interlamellar spacing between Nd-rich platelets of the alloy was small, resulting in a lower saturated magnetization due to increased amounts of small particles after jet milling. With further decreasing cooling rate, the resultant larger interlamellar spacing led to too large particle sizes as well as a more irregular shape; thus deteriorated the magnetic properties of the final magnet. A model was developed to disclose the effects of particle sizes on the magnetic alignment process. In the current investigation, optimum magnetic properties of the final magnets were obtained with a cooling rate of 2.6m/s for preparing the strip. The magnets made by conventionally cast ingot technique exhibited the lowest magnetic properties because of the slowest cooling rate. [Copyright &y& Elsevier]

Abstract: Effects of the dehydrogenation of the hydrogen decrepitated (HD) powders on the magnetic properties and the fracture strength of sintered NdFeB magnets were studied. It was found that the lattice parameters and the crystal phase of NdFeB changed significantly with the various hydrogen contents of the resultant HD powders due to the different degrees of dehydrogenation. The magnetic properties and fracture strength increased with decreasing hydrogen content, reaching the maximum increases of 200% for both intrinsic coercivity and bending strength, which can be ascribed to the improved microstructure of the sintered NdFeB magnets. The hydrogen remaining in the HD powders diffused out and affected drastically the grain and grain boundaries by the hydrogen out-take channel during the subsequent sintering process. [Copyright &y& Elsevier]