The absolute unrelaxed surface energy and its full orientation-dependent behaviour of 13 HCP metals are studied via a broken-bond base geometric model. The model is integrated with the Rose-Vinet universal potential to investigate arbitrary orientations which are not assessable by other methods. Using only three materials constants, the calculated results show only marginal discrepancies with reported experimental values, except for divalent sp metals Mg, Zn and Cd where the calculated values are lower by a factor of 2. Stereographic projections of all 13 metals show global minimum on (0001) pole with an overall anisotropy of 15% to 21%. The equilibrium crystal shape of HCP is found to be truncated hexagonal bi-prismatic, with (0001) always favoured but the bi-prismatic facets vary from one metal to another. All projection patterns show strong six-fold symmetries but are unique for every element. The patterns are found to be largely determined by an anharmonicity factor η. Best agreement with experimental findings are found for Be, Sc, Ti,Y, Zr and Hf which possess comparatively low η. We believe the stereographic projections of these elements are the more representative for HCP metals.
This work reports the refinement of pearlite structure into nanostructure using electropulsing. Nanostructured pearlitic steel wires possess nanoscale lamellae or nanoscale grain microstructures. Fabrication of nanostructures by severe plastic deformation and lamellar to grain transformation have been investigated. It is suggested that an aligned pearlite structure is preferred in severe plastic deformation. The lamellar to grain transformation is controlled by diffusion of carbon within cementite and also from cementite to ferrite phases.Carbon mobility is changed by mechanical, thermal and electrical states. The interface between nanoscale sub-grains in the ferrite phase has considerable carbon content. Numerical calculations and experimental observations demonstrated these mechanisms.
Surface energy anisotropy (SEA) has long been a hot topic in interface science as it has an important role in the interface/surface behaviours for crystalline phases. Most studies aim to determine the numerical values of the anisotropic surface energy in some particular orientations, but few investigate the whole orientation-dependent trend, or the morphology of the polar plot. The present work propose descriptions for SEA of both body centred cubic (BCC) and face centred cubic (FCC) metals by considering the interactions between an atom and its 1st, 2nd and 3rd nearest neighbouring (NN) atoms. The expression makes use of only three coefficients K1, K2 and K3 which are correspondent to the contribution of 1st, 2nd and 3rd NN interactions respectively. This allows estimation of surface energy for all crystallographic orientations if the values for (111), (100) and (110) orientations are provided. Matching of our model with modified analytical embedded-atom method (MAEAM) results demonstrates less than 0.5% average relative error. We also construct the polar plots of BCC metals based on our model and compare them with some other models.
A broken-bond type computational method has been developed for the calculation of the five-dimensional grain boundary energy. The model allows quick quantification of the unrelaxed five-dimensionally specified grain boundary energy in arbitrary orientations. It has been validated on some face-centred cubic metals. The stereo projections of grain boundary energy of Σ3, Σ5, Σ7, Σ9, Σ11, Σ17b and Σ31a have been studied. The results of Ni closely resemble experimentally determined grain boundary energy distribution figures, suggesting the overall anisotropy of grain boundary energy can be reasonably approximated by the present simple model. Owing to the overlooking of relaxation matter, the absolute values of energy calculated in present model are found to be higher than molecular dynamic based results by a consistent magnitude, which is 1Jm −2 for Ni. The coverage of present method forms a bridge between atomistic and meso-scale simulations regarding polycrystalline microstructure.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.