Site Occupancy of Chrome in the Gamma Prime Phase Ni3Al: An Integrated Computational and Experimental Study (Preprint)

摘要

The mechanical properties of Ni-base superalloys are strongly influenced by ordered gamma'-Ni3Al precipitates, whose growth and coarsening are controlled by the site occupancy of elements within the structures. The site occupancy behavior of Cr in gamma'-Ni3Al is investigated by ab initio based Density Functional Theory based computational studies and 3D atom probe tomography. Three formalisms related to site occupancy are discussed, including standard defect formation formalism, antisite based formalism, and vacancy based formalism. The calculated substitutional energies of the Cr atom at the Ni and Al sublattice sites indicate that Cr has a strong preference for the Al site. Comparisons between the formalisms indicate that standard defect formation formalism gives an inconsistent result and vacancy based mechanism will dominate in the substitution process. The effect of additional Cr atoms calculated by the interaction energies of two Cr atoms suggests that Cr atoms prefer to be on nearest neighbor lattice sites: either in the Al, Ni, or mixed sublattice sites.