Thermoelectric effects induced dendrite branching dynamics in pure substances: An insight from morphological theory.

Insights on the mechanical behavior in materials highly depend upon sufficiently characterizing microstructure details at the relevant length scales. In this study, the side-branching dynamics of dendritic structures formation in pure substances is studied upon the phase-field simulations of crystallization with applied direct currents. The effect of heat diffusion (including thermoelectric effect and undercooling) on the dendritic development is investigated, and the characteristics of the primary arms and side-branches are identified by implementing the image recognition technique. Results indicate that increasing the latent heat release would firstly enhance the side-branching and then cause the side-branches re-melting with large heat extraction form the solid. The side-branching could be tailored by rationally controlling the applied electric filed as well the heat treatment, which could be a potential way to improve the mechanical properties in metallic materials via optimizing the microstructure.

Effect of CeO2 on the microstructure and microhardensss of laser-cladded Ni60 on 35CrMoV alloys.

In present work, the effect of CeO2 addition on the crack susceptibility, microstructure, phase composition, solute segregation and microhardness of Ni60 cladding layer was investigated. The coatings were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS) and microscopic vickers hardness tester. The results show that main phase composition of Ni60 cladding layer are Ni3Fe, Ni3V, Ni3B, Cr23C6, Fe5C2. The microhardness of the cladding layers from the surface to the substrate is gradually decreased with increasing depth of the cladding layer. With increasing addition of CeO2, the diffraction peak of XRD is shifted to the left, indicating the lattice distortion in the phases of the coating. Compared with other cladding layers with different contents of CeO2, the solute distribution of Ni60 cladding layer containing 4.0 % CeO2 is more uniform, and the cross-section structure is more compact and homogeneous. The results show that the addition of 4.0 % CeO2 can effectively inhibit the cracks and porosity, promote grain refinement, and improve the microstructure homogeneity in the Ni60 cladding layer.