Journal of Materials Science, Vol.54, No.21, 13609-13618, 2019
When a defect is a pathway to improve stability: a case study of the L1(2) Co3TM superlattice intrinsic stacking fault
Effect of solutes of transition metals (TM = Cr, Fe, Hf, Mn, Mo, Nb, Ni, Pt, Rh, Ru, Re, Ta, Ti, V, W, Y and Zr) on the local phase transition between the L1(2) and D0(19) structures in superlattice intrinsic stacking fault (SISF) of Co3TM has been investigated. All the models employed herein, i.e. (1) the SISF-containing supercell, (2) the axial nearest-neighbor Ising (ANNI) model, and (3) both the L1(2)- and D0(19)-containing (L1(2) + D0(19)) supercell, yield the same result regarding the stability of SISF in L1(2)-type Co3TM. In the view of bonding charge density, the atomic and electronic basis of local D0(19) phase transition in the SISF fault layers of Co3TM are revealed. Especially, the negative SISF energy predicted by the L1(2) + D0(19) model suggests that both the SISF fault layers (i.e. the local D0(19) structure) and the L12 phase of Co3TM can be stabilized through a coupling interaction between the fault layers and the solutes, paving a pathway to stabilize Co-base superalloys via Co3TM precipitate. Moreover, the consist results of E-SISF via the ANNI model with the classical SISF-supercell method utilized in first-principles calculations supports the approach to efficiently distinguish various planar faults and predict their corresponding energies, such as SISF, superlattice intrinsic stacking fault, anti-phase boundaries, and so on.