In this study, 6061 aluminum alloy and AZ31B magnesium alloy composite plate was fabricated through explosive welding. Molecular dynamics (MD) simulations were conducted to investigate atomic diffusion behavior at bonding interface in the Al/Mg composite plate. Corresponding experiments were conducted to validate the simulation results. The results show that diffusion coefficient of Mg atom is larger than that of Al atom and the difference between these two coefficients becomes smaller with increasing collision velocity. The diffusion coefficient was found to depend on collision velocity and angle. It increases linearly with collision velocity when the collision angle is maintained constant at 10° and decreases linearly with collision angle when the collision velocity is maintained constantly at 440 m/s. Based on our MD simulation results and Fick’s second law, a mathematical formula to calculate the thickness of diffusion layer was proposed and its validity was verified by relevant experiments. Transmission electron microscopy and energy-dispersive system were also used to investigate the atomic diffusion behavior at the bonding interface in the explosively welded 6061/AZ31B composite plate. The results show that there were obvious Al and Mg atom diffusion at the bonding interface, and the diffusion of magnesium atoms from magnesium alloy plate to aluminum alloy plate occurs much faster than the diffusion of aluminum atoms to the magnesium alloy plate. These findings from the current study can help to optimize the explosive welding process.

Magnesium alloys AZ31B plates and pure titanium TA2 plates were bonded successfully through explosive welding. The microstructure and composition of the interface were examined by optical microscope (OM), scanning electron microscopy (SEM) and energy dispersive spectroscope (EDS). To explore the process of element diffusion between AZ31B and TA2, the composite plates were annealed at different temperatures. Furthermore, the mechanical behavior of the composite plates was evaluated. The results show that straight and wavy interfaces coexist on the bonding area. The element diffusion becomes obvious when heating at 450 and 490 °C for 4 and 8 h. The hardness of AZ31B and TA2 is increased significantly due to the plastic deformation and the strain hardening. The mechanical properties of the composite plates are significantly improved compared with those of base plate AZ31B.

•B4C/6061Al laminar composite fabricated by Power metallurgy.•The grains around B4C particles are smaller that away from B4C particles, which is propitious to development of a recrystallization nucleus.•The strength of the rolled B4C/6061Al laminar composite is obviously enhanced while the elongation to fracture is reduced compared with the extruded laminar composite.This study aims to investigate the effects of compositional gradient on microstructure and mechanical properties of a B4C/6061Al laminar composite fabricated using a powder metallurgy method - spark plasma sintering followed by extrusion and hot rolling. Results show that B4C particles were distributed fairly uniformly in the fabricated composites. Interfaces among different layers in the composites were bonded well and no porosity were observed in transition regions among different layers. The grains around B4C particles are smaller than those away from the B4C particles. Stress concentration is found to occur easily at the tip of the B4C particle, which facilitates the development of recrystallization nuclei. Compared with those of an extruded B4C/6061Al laminar composite, yield strength and ultimate tensile strength of the rolled B4C/6061Al laminar composite are obviously enhanced but its elongation to fracture is weakened. Two yielding points were observed in the rolled three-layer B4C/6061Al laminar composite due to the existence of B4C content gradient in the composite. Strengthening mechanisms in the fabricated laminar composites include grain refinement, dislocation strengthening, load transfer effect, and Orowan strengthening.

In this study, electrochemical corrosion tests, full-soak corrosion tests and associated microstructure analysis were conducted to investigate the corrosion behaviors of B4C/6061Al neutron absorber composites (NACs) manufactured by powder metallurgy method in solutions having different boric acid (H3BO3) concentrations (500, 2500 and 10,000 ppm). In electrochemical corrosion tests, B4C/6061Al NACs demonstrate the highest (short-term) corrosion resistance in the 2500 ppm H3BO3 solution. While for full-soak corrosion tests, the B4C/6061Al NACs show the highest (long-term) corrosion resistance in the 500 ppm H3BO3 solution. This difference is found to be mainly due to the formation of different surface morphologies during these two different corrosion tests. As noticed, a layer of Al(OH)3 was formed on the composite surface during full-soak corrosion tests, but it cannot be found in the electrochemical corrosion tests. The full-soak corrosion mechanism of the B4C/6061Al NACs in the H3BO3 solution is found to be primarily determined by the dynamic balance between the formation and dissolution rates of the oxide film, which is mainly controlled by the density of H+ ions in the solution.

•B4C/Al composites for neutron shielding were designed by MCNP program.•B4C/Al composite were fabricated by vacuum hot pressing followed by hot rolling.•The properties can be enhanced by vacuum hot pressing followed by hot rolling.Based on the Monte Carlo Particle transport program MCNP, a novel boron carbide particulate reinforced 6061Al composite for neutron shielding (B4C/6061Al NACs) with high strength and low density was designed. The NACs with four volume fractions (10%, 20%, 30% and 40%) were successfully fabricated by vacuum hot pressing followed by hot rolling (VPHR) in atmospheric environments. The calculation results indicated that the neutron transmission ratio decreased with the increasing of B4C content and the thickness of plates. B4C particle is uniformly distributed in the matrix, exhibiting the good bonding in interface. The phases of neutron absorbers were mainly B4C and Al, and a spot of AlB2 and Al3BC. The grain of the matrix was refined and the dislocation was formed around the particles. With increasing the B4C content, the particles gathered, breakage appeared, and the tensile strength of composite first increased and then decreased. The failure mode of B4C/6061Al NACs included: the interfacial debonding and the cleavage fracture of particles.

•1.7 mm Zr-based amorphous coating was prepared on A283 by laser solid forming.•Amorphization ratio from bottom to surface in the coating was revealed.•The influence from the melted substrate for crystallization was investigated.•The corrosion resistance of Zr-based amorphous coating was evaluated.Multi-layer Zr65Al7.5Ni10Cu17.5 amorphous coatings were produced by laser solid forming on A283 substrate. The coatings with few pores and free of cracks had good metallurgical bonding with the substrate. The microstructural characterization, phase composition, chemical component distribution and corrosion behavior of the coatings were investigated. The results revealed that the amorphization degree increased from the substrate to the coating surface mainly due to the dilution and stir influence from the melted substrate. In the five layers coating, the volume fraction of amorphous phase in the 5th layer, 3rd layer and 1st layer was about 77%, 64% and 49% respectively. With regard to corrosion property, potentiodynamic polarization plots, Nyquist plots and the equivalent circuits were employed in 3.5 wt% sodium chloride solution. Attributing to the presence of amorphous phase and passivation, the LSF coatings exhibit excellent corrosion resistance.

Aluminum 6061 matrix composite reinforced by 35 wt% B4C particle was fabricated by power metallurgy method. Then, the as-deformed composite was tested by quasi-static (0.001 s−1) and dynamic (760–1150 s−1) compression experiments. The Johnson–Cook plasticity model was employed to model the flow behavior. The damage mechanism of composite was analyzed through the microstructure observations. The results showed that the B4C particles exhibited uniform distribution and no deleterious reaction product Al4C3 was found in the composite. Al6061/B4C composite showed high yield strength, moderate strain rate sensitivity and strain hardening under the dynamic loading, and a constitutive model under dynamic compression was established based on Johnson–Cook model, and accorded well with experimental results. The microstructure damage was dominated by particle fracture and interface debonding, and the dislocation was observed in the composite at a higher strain rate.

In order to obtain extremely rapid solidification structure far from equilibrium, the surface of AZ31B magnesium alloy was melted by CO2 laser, while the samples were extremely rapidly cooled in liquid nitrogen. The microstructure, the performance and the strengthening mechanism of the laser melted layer were investigated. The results show that grains of the melted layer are highly refined and the grain size is nearly uniform. The melted layer contains α-Mg and β-Mg17Al12, but β-Mg17Al12 which distributes along the grain boundary is few. Because of strengthening mechanisms of fine grains, super solid solution and dislocation, microhardness HV of the melted layer is up to 1400 MPa. Wear loss of the melted sample cooled in liquid nitrogen is about 50% less than that of the untreated sample and the melted sample cooled in air, and wear resistance of the melted layer is improved obviously. Impacting fracture morphology indicates that there is a trace of plastic deformation, thus, improving plasticity and ductility.

The superficial temperature evolution of 10 mm-thick extruded AZ31B magnesium alloy plate was measured during the high-cycle fatigue test. The mechanism of heat generation was analyzed according to the law of energy conversion. The temperature fluctuation during the fatigue test was related to the cyclic hardening/softening process which was discussed according to the followed tensile tests. The temperature evolution was also measured during tensile tests. The influence of cyclic hardening/softening process on the change of thermoelastic effect in tensile tests was also discussed. Finally, the density evolution of dislocation was related to the energy change during fatigue tests.