Search

The effect of La/Nd ratio on the microstructure and tensile properties of AZ91-RE alloys was studied. Typical characterization was performed to analyze the volume fraction, mean nearest neighbor distance (NND), and number density of the secondary phases. First-principles calculations were employed to determine the formation enthalpy, mechanical and thermodynamics properties of the secondary phases. The results demonstrate that the alloy with a mass fraction ratio of La to Nd (wLa/wNd) of 3:2 exhibits the finest average grain size, the smallest mean NND, and the highest total number density of secondary phases. The calculations indicate that the formation of Al11La3and Al2Nd is energetically favorable. Furthermore, Al11La3and Al2La display significantly superior deformation resistance, shear deformation resistance, solid stiffness and thermal stability compared to other secondary phases. Therefore, increasing the content of Al11La3and Al2La phases contributes to improving the mechanical properties of AZ91-RE alloy.

This study investigated the effect of extrusion ratio on the microstructural evolution and mechanical properties of the as-extruded short carbon fibers (SCFs) reinforced AZ31 alloy composite, and the microstructural development of the composite during extrusion was thoroughly investigated. The dominant dynamic recrystallization (DRX) mechanisms are particle simulated nucleation, continuous DRX, and discontinuous DRX. The addition of SCFs promotes the dynamic recrystallization during hot extrusion. As extrusion ratio increases, the interfacial bonding degree of the composite increases gradually, and the composite with an extrusion ratio of 25:1 exhibits the finest DRXed grains and the best mechanical performance with a yield strength of 171 MPa, an ultimate tensile strength of 258 MPa and an elongation of 6.0%. The enhanced strength is mainly attributed to grain refinement strengthening and dislocation strengthening, which are induced by the DRXed grains and the added SCFs.

Ni–La2O3/CeO2composite films were prepared by electrodeposition from a nickel sulfate bath containing certain content of micrometer and nanometer La2O3/CeO2particles. The effect of La2O3or CeO2particle size on the oxidation resistance of the electrodeposited Ni–La2O3/CeO2composites in air at 1000 °C was studied. The results indicate that, compared with the electrodeposited Ni-film, Ni–La2O3/CeO2composites exhibit a superior oxidation resistance due to the codeposited La2O3or CeO2particles blocking the outward diffusion of nickel. Moreover, compared with nanoparticles, La2O3or CeO2microparticles have stronger effect because La2O3or CeO2microparticles also act as a diffusion barrier layer at the onset of oxidation.

Based on the synthetical effect of composite additives and phase transformation, the influence of different contents of Cu on the microstructure, the toughening mechanism and routes of Al 2O 3ceramic was investigated by XRD, SEM and Vickers sclerometer, etc. The results showed that the grain of Al 2O 3obviously presented anisotropic growth, and the accumulation effect occurred between toughening effect of Al 2O 3and phase transformation and self-toughening. The density of the experimental materials was close to theoretical density. The bending strength and fracture toughness were improved significantly.