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The mechanism for outstanding resistance to He-ion irradiation-induced hardening of a novel dispersion-precipitation strengthened NiMo alloy has been investigated. Microstructural observations show the interface between Mo2C micro-particles and Ni matrix and between SiC nanoparticles and Ni matrix can effectively trap He bubbles, thus synergistically inhibiting the formation and growth of the dissociated He bubbles in the Ni matrix. It suggests that the reasonable high amounts of well-dispersed Mo2C micro-particles and SiC nanoparticles can effectively improve the inhibition efficiency of irradiation-induced hardening and are beneficial for the optimization and design of irradiation-resistant Ni-based alloys.

Cobalt-free Li-rich Mn-based cathode materials are considered to be the next generation of Li-ion batteries due to low cost, high discharge capacities and high safety feature. However, there are still several serious issues that need to be solved urgently, such as low initial coulombic efficiency, low rate capability, poor cycling performance and voltage fading. Na doping or substitution is introduced to improve the electrochemical performance of Li1.2Mn0.6Ni0.2O2 cathode material, which is synthesized by sol-gel method. The effect of Na doping or substitution on the morphological, structural and electrochemical properties was systematically studied and analyzed by scanning electron microscope (SEM), X-Ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), cell test system and electrochemical workstation. These results illustrate that lattice layer spacing is enlarged by Na doping or substitution, which is beneficial for the diffusion of Li-ion, and the voltage fading is successfully suppressed. The best electrochemical properties were obtained when Na doping, which is attributed to the stronger structural stability and better reversibility of Li+ during the initial charge and discharge process.

Exploring efficient and stable non-precious metal electrocatalysts for oxygen reduction reaction in neutral and alkaline solutions is of great importance for metal-air batteries. Herein, an efficient and stable electrocatalyst with CoNi nanoalloy (10-20 nm) uniformly embedded in porous N-doped carbon framework (CoNi-NCF) for neutral and alkaline primary Al-air batteries is prepared and studied. The CoNi-NCF electrocatalyst shows superior ORR performance in terms of half-wave potential of 0.91 V in 0.1 M KOH solution and 0.64 V in 3.5 wt% NaCl solution, outperforming those of the commercial Pt/C catalyst. Supported by in situ electrochemical Raman spectra and density functional theory calculations, the rich dual active sites of CoNi nanoalloy and porous N-doped carbon contributes to the outstanding ORR performance. Impressively, when employed as a cathode catalyst in both aqueous and solid flexible Al-air batteries, the CoNi-NCF-based Al-air batteries show the highest discharge performance, long-time durability and high flexibility, demonstrating the promising potential for practical application.

The effects of chromium content on microstructure, hardness and wear resistance of as-cast Fe-xCr-1.0B (x = 0, 4, 8, 12, 16, 20) alloys were investigated by means of optical microscope (OM), scanning electron microscope (SEM), x-ray diffractometer (XRD), hardness tester and ring block wear tester. The results showed that the microstructures of chromium-free alloy were mainly composed of pearlite, ferrite, and eutectic borocarbides, and the hardness was very low, only 18.8 HRC. With the increase in chromium content, the matrix of as-cast Fe-Cr-B alloy gradually began to transform from pearlite and ferrite to lath martensite, and the type of borocarbides changed from Fe2(B, C) to M2(B, C), M7(C, B)3 and M23(C, B)6 (M = Fe, Cr). When the chromium content was 12 wt.%, the hardness of alloy reached the highest value of 61.1 HRC, and the wear resistance of alloy was the best. The results of worn surface analysis showed that the wear failure of as-cast Fe-Cr-B alloy was mainly caused by multiple plastic deformation and micro-cutting.

Ni-Mn-Ga microfiber with a diameter of 80 μm was produced by glass-coated melt spinning method. The martensitic transformation temperature, TM, and the reverse transformation temperature, TA, is 279 K and 290 K, respectively. The as-cast microfiber shows nearly fully recoverable superelastic strain as large as ~10%, and perfect strain-magnetization effect, as the stress-induced martensite has lower initial susceptibility and higher saturation magnetization than the austenite. It will be a potential non-destructively and noncontactually monitor sensor material.

A periodic-layered structure was observed in solid-(Cr, Fe)2B/liquid-Al diffusion couple at 750 &deg, C. The interface morphology, the reaction products, and the potential formation mechanism of this periodic-layered structure were investigated using an electron probe microanalyzer (EPMA), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and energy-dispersive spectroscopy (EDS). The results indicate that the reaction between (Cr, Fe)2B and liquid Al is a diffusion-controlled process. The formation of intermetallics involves both the superficial dissolution of Fe and Cr atoms and the inward diffusion of Al at the interface. The layered structure, as characterized by various experimental techniques, is alternated by a single FeAl3 layer and a (FeAl3 + Cr3AlB4) dual-phase layer. A potential mechanism describing the formation process of this periodic-layered structure was proposed based on the diffusion kinetics based on the experimental results.

In this study, a high aluminum and chromium Fe-B-C coating was prepared using laser cladding on 2Cr13 steel substrate. The microstructure, microhardness, and wear resistance of the high aluminum and chromium Fe-B-C coating were investigated. The results show that this dense coating possesses good metallurgical bond with the substrate. The microstructure is mainly composed of &alpha, (Fe, Cr, Al) lath martensite, orthorhombic M2B boride, orthogonal M3C2, and orthorhombic M7C3 carbides. The microhardness of the coating can reach 620 HV which is 3.3-times higher than that (190 HV) of the substrate. The coating shows a lower friction coefficient of 0.75 than that of the substrate (1.08). The wear rates of the substrate and the coating are 0.295 mg/min and 0.103 mg/min, respectively, indicating the coating exhibits excellent wear resistance. The wear mechanism transforms severe adhesive wear and abrasive wear of the substrate to slight abrasive wear of the coating. The results can provide technical support to improve the properties of the Fe-based laser cladded coating.

Ni-rich cathode material is one of the most promising material for Li-ion batteries (LIBs) in portable power and electric vehicles. However, how to recycle waste LIBs cathode materials is very important for environmental protection and resource utilization. LiNi0.6Co0.2Mn0.2O2 cathode materials were prepared by sol–gel combustion method Using waste LIBs cathode materials as raw materials. The effect of different gels on the crystal structure and morphology of LiNi0.6Co0.2Mn0.2O2 were studied by X-ray diffraction and scanning electron macroscopy. The electrochemical properties were investigated by charge–discharge testing, cyclic voltammetry and electrochemical impedance spectroscopy. The results showed that the samples contained some residual C and primary crystals have been formed during combustion stage. When glucose was used as gel regent, the sample has the good electrochemical properties with the initial discharge capacity of 176.9 mAh g−1, initial coulombic efficiency of 87.0% and discharge capacity retention rate of 95.8% after 50 cycles at 0.2 C rate. The results showed that the less the cation mixing, the more complete of hexagonal crystal structure, which induced the decrease of impedance resistance and good reversibility of redox reaction.

Laser butt welding was carried out for the joining of 5A06 aluminum alloy sheet by using 6 KW fiber laser. The effect of welding speed on the surface morphology, microstructure, micro-hardness, tensile strength and porosity were studied by means of optical microscopy (OM), a scanning electron microscope (SEM), an energy dispersive spectrometer (EDS), a Vickers hardness tester and a universal mechanical tensile test. The results show that the weld macro morphology tends to be smooth and the surface defects are reduced with an increase in welding speed. The heat-affected zone was very small due to the large cooling rate. The columnar dendrites grow from the fusion line along the direction of the temperature gradient. The microstructure of the weld zone was in the form of equiaxed grains. The micro-hardness of the weld was lower than that of the base material. The micro-hardness and the tensile strength were gradually increased with an increase in welding speed. When the welding speed is 12 mm × s−1, the micro-hardness and the tensile strength were increased to 96.5 % and 56.2 % of the base mental, respectively. The porosity ratio decreased at first, and then increased with the increase in welding speed. The lowest porosity ratio was 1.99 % when the welding speed was 12 mm × s−1. In summary, the quality of the weld was better when the welding speed was 12 mm × s−1.

Effective oxidation control of metal materials is a long-standing challenge. Here we show a new strategy for oxidation control induced by nanoparticles (NPs). The results demonstrate that the in situ formed NPs can promote the formation and growth of a continuous and dense protective oxide scale while enhancing its adhesion with the matrix. Furthermore, the assembly of NPs on the grain boundaries (GBs) and phase boundaries (PBs) can be effective in stifling the inward diffusion of oxygen ions and the outward diffusion of cations. The effectiveness of this approach is verified in FeCr alloys in high temperature conditions. Our approach can break through the inherent limitations of conventional alloying treatment, e.g. the detrimental element interaction, the high costs and limited availability of noble metals and rare earth elements, which may pave a new avenue for the remarkable improvement in the oxidation resistance of metal materials.

In this work, in situ nanoparticles (TiB2 and TiC) can be demonstrated to induce significant improvement in the oxidation resistance of Fe-12 wt.%Cr-3.5 wt.%B alloys. To unravel the roles of nanoparticles in the anti-oxidation of Fe-12 wt.%Cr-3.5 wt.%B alloys, samples with various nanoparticle contents were synthesized to investigate their oxidation resistance. Results show that nanoparticles facilitate the formation of a continuous and dense Cr2O3 protective film and enhance its adhesion with the matrix. Furthermore, the nanoparticle assembly on the surface of borides can inhibit the inward diffusion of oxygen ions and the outward diffusion of cations, thereby effectively controlling the growth of oxide scales.

CoCrFeNi and CoCrFeNiAl0.3 high entropy alloys reinforced with in-situ oxide nanoparticles have been successfully fabricated by mechanical milling in combination with hot pressing and hot extrusion. The as-fabricated CoCrFeNi samples exhibited an ultrafine grained microstructure with in-situ Cr2O3 oxide nanoparticles formed during hot pressing and extrusion process and distributed both on grain boundaries and in grain interiors. Increasing extrusion temperature from 1000 to 1100 °C caused a significantly increase of grain size from 700 nm to 2.5 μm owing to recrystallization and growth of the recrystallized grains, as well as the coarsening of Cr2O3 nanoparticles with their mean size increasing from 57 to 140 nm. When adding Al elements, finer Al2O3 nanoparticles (mean size: 30 nm) formed in the CoCrFeNiAl0.3 high entropy alloy, leading to refinement of the grains (mean size: 504 nm) due to their pinning effect on grain boundary immigration. After T6 heat treatment, the CoCrFeNiAl0.3 high entropy alloy demonstrated improved mechanical properties with yield strength of 1335 MPa, ultimate tensile strength of 1346 MPa and an elongation to fracture of 7.9%. With quantitative analysis based on the current models, it was concluded that grain boundary strengthening and Orowan strengthening acted as the dominant strengthening mechanisms.

In this study, the SiC/Al-Zn-Mg-Cu nanocomposites were fabricated using high energy ball milling combined with spark plasma sintering (SPS) and hot extrusion. The microstructure and mechanical properties were investigated by utilizing X-ray diffraction (XRD), scanning electron microscopy (SEM) and high resolution transition electron microscopy (HRTEM) analysis as well as tensile tests. The results showed that the as-extruded SiC/Al-Zn-Mg-Cu nanocomposite samples demonstrated a microstructure consisting of ultrafine α-Al grains, dispersed SiC nanoparticles and nano-scaled T phases probably formed by dynamic precipitation during extrusion. After T6 heat treatment, the coarsening of α-Al grains, dissolution of T phases and consequently the precipitation of fine η′ phases occurred, leading to a simultaneous increase of the strength and ductility. With increasing the content of SiC nanoparticles from 1 vol% to 3 vol%, the yield strength (YS) and ultimate tensile strength (UTS) increased from 456 and 528 MPa to 580 and 588 MPa (27.2% and 11.4% increase), respectively while the elongation to fracture decreased slightly from 11.8% to 10.2% (13.6% decrease). Various strengthening mechanism calculation results show that Orowan strengthening was mostly contributed to the improved strength of the T6 heat treated SiC/Al-Zn-Mg-Cu nanocomposites.

Ti–6Al–4V alloys are utilized in various industrial applications. Here, the effect of heat treatment on the microstructural evolution and mechanical properties of the Ti–6Al–4V alloys, which were fabricated by selective laser melting (SLM), was investigated. The as-fabricated-1133 K sample possessed a significantly higher ductility than that of the as-fabricated sample. This was attributed to the precipitation of the micro/nanoscale β and athermal ω phases that was accompanied by the equiaxial transformation of the β columnar grains.

The Fe-B-Al alloy containing 0 to 10.0 wt.-% Al was melted in a vacuum induction furnace. Effects of the aluminum addition on the microstructure and properties of Fe-B-Al alloys were studied by means of optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), hardness testing and MMG-500 type pin-on-disk high temperature vacuum wear testing. The results showed that the as-casted microstructure of the aluminum-free Fe-B alloy consisted of α-Fe, Fe2(B,C), and Fe23(B,C)6 type borocarbides. However, the as-casted microstructure of the Fe-B-Al alloy consists of a Fe3Al type intermetallic compound when the aluminum content is more than 6.0 wt.-%. Compared with the aluminum-free Fe-B alloy, parts of the borocarbide networks are broken, and the fracture tendency became more obvious with the increase of the aluminum content. Boron is mainly distributed over the borocarbide. Aluminum is mainly distributed over the matrix and Fe3Al type intermetallic compound. Compared with the aluminum-free Fe-B alloy, the addition of a small amount of aluminum reduces slightly the hardness. The hardness gradually increased with the further increasing of the aluminum content. The hardness reached 48.1 HRC when aluminum content was 10.0 wt.-%. The high temperature wear resistance of Fe-B-Al alloy gradually increased with the increase of the aluminum content. When the aluminum content reached 10.0 wt.-%, the high temperature wear resistance of the alloy was the best.

In this paper, the high-temperature oxidation behaviors at 900 °C of the conventional laser metal deposition (LMD) and extreme high-speed laser metal deposition (EHLMD) high chromium K648 superalloys were comprehensive studied. The experimental results reveal that the oxidation resistance of the LMD K648 superalloy is better than the EHLMD K648 superalloy. The oxidation films of LMD and EHLMD K648 superalloy consists of continuous Cr2O3 film and an internal wedge-shaped Al2O3. The oxidation process is mainly controlled by the outward diffusion of oxide-forming elements and the inward penetration of oxygen.

In this work, we employed first-principles calculations to investigate the stability, electronic structures, mechanical and thermodynamic properties of FexAlyCz compounds which were first observed in Fe-Cr-B-Al-C alloy. The results reveal that the FexAlyCz compounds are thermodynamically stable, and the addition of C element improves the stability of FexAlyCz compounds. These FexAlyCz compounds display disparate anisotropy according to different calculated 3D curved surfaces of Young's modulus and anisotropic index. The Fe3AlC compound has the biggest shear modulus, bulk modulus and Young's modulus with the values of 141.2 GPa, 212.6 GPa and 346.8 GPa, respectively, which indicates that the Fe3AlC compound has the largest rigidity, lateral deformation resistance and good solid compressibility under static pressure. The ratio of G/B shows that FeAl and Fe3AlC are brittle phases, while the Fe3Al and FeAl3 phases appear to be ductile. The calculated electronic structure reveals that the bonding characteristics of the FexAlyCz compounds are the mixture of both metallic and covalent bonds, which also exhibits anti-bond effects. The Fe3AlC compound has the biggest Debye temperature of 702.2 K. Meanwhile, the hardness of Fe3AlC is 19.4 GPa which is three times of the Fe3Al compound. The results obtained in this study provide a theoretical basis for the applications of Fe3AlC compound in Fe-Cr-B-Al-C alloys.

The effect of temperature on the oxidation resistance of a novel wear-resistant Fe-10Cr-1.5B-6Al-0.3C-0.8Mn-0.6Si alloy is investigated. The mass growth rate shows that this alloy exhibits superior oxidation resistance at 900 °C. As the oxidation temperature increases from 900 °C to 1100 °C, the structure of the observed oxide scales transforms from a porous bilayer to a flat monolayer, while the oxidation rate increases sharply. The selective oxidation of Al suppresses the outward diffusion of Cr and Mn to form MnCr2O4 oxides in the monolayer oxide scale, thereby decreasing the oxidation resistance at 1100 °C.

A high chromium (Cr) superalloy, K648, has been additively fabricated by using laser metal deposition (LMD) for the first time, and the microstructure and mechanical properties of the deposits are investigated. The results show that the main phases of the K648 superalloy are γ-Ni, γ′, α-Cr and M23C6. The microstructure from the bottom to the middle region is mainly composed of epitaxially grown columnar dendrites, and the microstructure in the top region is mainly equiaxed grains. Element segregation exists in the LMD K648 superalloy. The average microhardness of the LMD K648 superalloy is about 220.5HV. The tensile strengths of LMD K648 superalloy show obvious anisotropic characteristics and the maximum ultimate tensile strength is about 833 MPa.

Mechanical properties, electronic properties, and Debye temperatures of NixBy (Ni3B, Ni2B, Ni4B3 and NiB) compounds were obtained by the first principles calculations based on the density functional theory (DFT). The results showed that the formation enthalpy of the NixBy compounds were stable with negative formation enthalpy. NiB had the largest B, G, and E, and the smallest &upsilon, it also had the highest hardness (10.8 GPa) and Debye temperature (681.8 K). Ni4B3 had the strongest anisotropy. It was found that the valence bonds of the NixBy compounds studied were composed of both metal bond and covalent bond, and the mechanical properties and Debye temperature of the NixBy compounds increased with the increase of the B atomic ratio.

The mould foot roller is a key component of a continuous casting machine. In order to investigate the possibility of using laser cladding to repair mould foot roller, Fe-based powders and 42CrMo steel are used in this work. The laser cladding process parameters were optimized by orthogonal experiments. The chemical compositions, microstructure, properties of the cladding layer under the optimum process parameters, and substrate were systematically investigated by using optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), microhardness test, wear test, and salt spray corrosion test. The results indicate that the primary factor affecting the width and depth of the cladding layer is laser power. The scanning speed also has a significant effect on the height of the cladding layer. The optimum process parameters for repairing the mould foot roller are 2 kW laser power, 4 mm/s scanning speed, and 15 g/min feeding rate of powder. Along the depth direction of the cladding layer, the microstructure of the coating gradually transforms from plane crystal, cell grains, or dendrites to equiaxed grains. The matrix is mainly martensite with retained austenite, the eutectic phase is composed of netlike M2B, particulate M23(C,B)6, and M7(C,B)3 phase. The hardness of the cladding layer is significantly improved, about three times that of the substrate. The weight loss of the cladding layer is just half that of the substrate. Its wear resistance and corrosion resistance have been significantly improved. The work period of the laser cladding-repaired foot roller is much longer than for the surfacing welding-repaired one. In summary, laser cladding technology can increase the life of mould foot rollers.