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Carbon fiber reinforced aluminum matrix composites (C f /Al) are widely used in various industries. But they are difficult to join because it is hard to realize the wetting and continuity of the carbon fiber in joint. To solve this problem, C f /Al are joined by ultrasonic soldering in this work. Results show that the C f /Al can be wetted within 5 s under ultrasonic. Transmission electron microscope result shows that the surface of the wetted carbon fiber is covered by an amorphous-nanocrystalline layer, which is formed due to the high solder velocity, temperature and pressure caused by cavitation. Carbon fibers flow into the solder after the Al matrix is eroded, guaranteeing its continuity in the joint. Limited carbon fibers flow into the joint at low ultrasonic power of 333.3 W, while a fully carbon fiber reinforced composite joint is obtained at 1000 W. The soldered joints have higher strength than the C f /Al substrate, and its formation mechanism is discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new process of diffusion bonding in air for Al–Mg–Li alloy was proposed, which greatly reduced the welding cycle and equipment requirements. • The Cu coating nano-interlayer not only inhibited the formation of oxide film but also promoted atomic diffusion. • The shear strength of Al-Mg-Li alloy joint was 187.9 MPa reaching up to 90.6% of that in BM. • The width of Al-Al diffusion interface was only about 1 μm and the joint was enhanced by nano-MgO. The process of diffusion bonding in air was successfully used to join 5A90 Al–Mg–Li alloy, which can greatly reduce the welding cycle and equipment requirements. Before diffusion bonding, the Cu nano-coating prepared on the surface of Al–Mg–Li alloy by ultrasonic electrodeposition was used as interlayer to hinder the formation of oxide film and increase the atomic diffusion. The effects of coating thickness, diffusion temperature and interlayer types on the microstructure and performance of joints were investigated. When the diffusion temperature was 530 °C and the coating thickness was 5.12 μm, the optimal shear strength of the joint with 1 μm-thick diffusing interface was 187.9 MPa, which was 90.6% of that in base metal. As the decomposition of unstable Li 20 Mg 6 Cu 13 Al 42 , Cu atoms diffused into the Al matrix to precipitate Al 6 CuMg 4 , and enhanced nano-MgO phase was formed in situ. In addition, the element diffusion behavior and formation mechanisms of the joints were discussed in detail. [ABSTRACT FROM AUTHOR]

• DFT and AIMD were combined to study the oxidation mechanism of CrN. • Surface energy of CrN low-index surface was calculated. • The adsorption configuration and electronic structure were analyzed. • The dynamics process of O 2 dissociation and adsorption was studied by AIMD. • The PDOS change during AIMD simulation were analyzed. [Display omitted] Density functional theory (DFT) calculation and ab initio molecular dynamics (AIMD) are combined to investigate the CrN oxidation mechanism. The surface energy, adsorption configuration and electronic structure of oxygen molecule and atom on the CrN (100) surface are investigated through DFT calculation. AIMD calculation is used to investigate the geometric configuration and electronic structure evolution of O 2 molecule adsorption and dissociation process at 1073 K. Results show that the (100) surface has the lowest surface energy. The top site of Cr atom is the most stable adsorption site for oxygen molecules and atoms, and the adsorption energy values are −4.276 eV and −4.975 eV, respectively. Charge density difference results show that both oxygen molecule and atom undergo charge transfer with the Cr atom. The O atom gains electrons while the Cr atom loses electrons. Results of partial density of states show that the Cr O bond is formed due to the hybridization between the O-p and Cr-d orbitals. At 1073 K, AIMD results show that the O 2 molecule automatically dissociates into O atoms, and the dissociated O atoms form stable covalent bonds with the surface Cr atom. The hybridization between the O-p and Cr-d orbitals gradually increases, thereby forming stable adsorption. [ABSTRACT FROM AUTHOR]

[Display omitted] • DFT and AIMD were combined to study the Ti 2 AlC oxidation mechanism. • Surface energy of different Ti 2 AlC (0001) surfaces was calculated. • The adsorption configuration and electronic structure were analyzed. • The dynamics process of O 2 dissociation and adsorption was investigated by AIMD. • The PDOS changing process during AIMD simulation was analyzed. Ti 2 AlC oxidation mechanism was investigated by density functional theory (DFT) and ab initio molecular dynamics (AIMD). DFT results showed that the most stable adsorption site was HCP hollow sites, followed by FCC. O atom gained electrons, while Al atom lost electrons through the hybridisation of O-p and Al-s/p orbitals. AIMD results show that O 2 molecule gradually dissociated into O atoms at 1273 K and formed Al-Ti mixed oxide film. The hybridisation between O-p and Al-s/p orbitals formed Al-O bond, while the hybridisation of O-p and Ti-d orbitals formed Ti-O bond. [ABSTRACT FROM AUTHOR]

This work focused on the microstructure, morphology and thermal stability of a MoNbTaTiV refractory high-entropy alloy synthesized by mechanical alloying. The mechanically alloyed powder with a uniform chemical distribution and an average grain size of less than 15 nm was obtained after 40 h milling process. With a refinement of the grain size and an increase of the lattice strain, the milled powder transformed from large and inhomogeneous to refined and homogeneous. The mechanically alloyed powder exhibited excellent thermal stability at 1200 °C. • MoNbTaTiV refractory high-entropy alloy was synthesized by mechanical alloying. • The alloyed powder presented a uniform chemical distribution and an average grain size of less than 15 nm. • The alloyed powder exhibited refinement and homogeneous size distribution. • The alloyed powder maintained bcc phase and nanoscale grain size at 1200 °C. [ABSTRACT FROM AUTHOR]