Electronic Structure And Multi-scale Behaviour For The Dislocation-doping Complex In The Gamma Phase Of Nickel-base Superalloys

Solid solution strengthening can be seen as an effective and rudimentary strengthening mechanism to promote the mechanical properties of alloys at finite temperatures.The prediction of the strength caused by solid solution strengthening involves not only the quantum effect of the interaction between the structure defect and doping atoms at the micro-scale,but also the calculations based on the theory of elasticity under the macro-scope,therefore,it can be considered as a classical multi-scale model.The lattice Green Function,as a multi-scale method,can succeed in providing the solution to achieving the coupling between different length scales.Refractory elements are added in the y phase of Ni-base superalloys to improve the creep strength.Many experiments show that in the primary creep stage,dislocations are mainly present in the y phase which lead to lots of dislocation-doping complex in y phase.Therefore,we studied the solid solution strengthening in the y phase of Ni-base superaloys with the Green Function to predict the strengthening effect of the alloying elements.Although Ta mainly partitions to γ’ phase,we take it together with those elements which partition toy phase to explore the factor affecting the solid solution.Based on the Green Function,the equilibrium dislocation core structure was obtained and the interaction energies between dislocation and doping atoms in dislocation core were calculated from first-principles.The results showed that the magnitude of interaction energies caused by doping atoms obey the order:Ta>W>Re.The detailed analysis of interaction energy suggest that the chemical interaction accounts for the most in the three doped system.Also electronic structure of dislocation-doping complex implies that hybridization between dislocation and Re is the most complicated.Combining the interaction energies calculated from first-principle and elasticity,we predicted the increased strength at OK and finite temperature.The prediction indicates that at low temperature Ta is the most potent strengthening solute,atoms with the largest size misfit with Ni exhibit the maximum strengthening.At high temperature,Re is the most efficient element to improve the creep life.The Re effect can be explained as the low diffusion coefficient,which can effective suppress the dislocation movement,and the strong partitions to the y phase.