Modelling ternary effects on antiphase boundary energy of Ni₃Al

Abstract

Abstract. The shearing of ordered γ precipitates by matrix dislocations results in the formation of antiphase boundaries (APB) in Ni-base superalloys. The APB energy is an important source of order-strengthening in disk and blade alloys where Ti and Ta substitute for Al in γ . While the importance of APB energy is wellacknowledged, the effect of alloying on APB energy is not fully understood. In the present study, the effect of Ti and Ta additions on the {111} and {010} APB energies was probed via electronic structure calculations. Results suggest that at low levels of Ti/Ta, APB energies on either plane increases with alloying. However, at higher Ti/Ta levels, the APB energies decrease with alloying. These trends understood by accounting for nearest neighbour violations about the APB and additionally, invoking the effect of precipitate composition on the energy penalty of the violations. We propose an Environment Dependent Nearest Neighbour Bond (EDNNB) model that predicts APB energies that are in close agreement to calculated values.

Atomic-scale modeling of superalloys

“…The energy of the APB that is formed during γ cutting of a dislocation is of central importance for shear resistance, see Chapter 6. Several recent works, including supercell DFT calculations [118][119][120][121] , DFT-based CE 122 , and DFT-based CPA 123 , showed consistently that alloying with group IV (e.g., Ti) and group V (e.g., Ta) transition-metal elements can considerably increase the APB energy and hence the shear resistance. Corresponding works for SISF and SESF were carried out with supercell DFT calculations 121,124 and AIM-based approximations 125 .…”

Precipitate Shearing, Fault Energies, and Solute Segregation to Planar Faults in Ni-, CoNi-, and Co-Base Superalloys

“…Mianroodi et al (145) studied the effect of Co in (Ni, Co) 3 Al by using molecular dynamics (MD) simulations, finding that the substitution of Ni with Co monotonically decreased the energies of the APB, CISF, and SISF. In the context of designing alloys for strength, the effect of alloying on APB energies has been extensively studied (125,128,142,(146)(147)(148)(149). Ta, Ti, and Nb have shown dramatic effects, while W, Mo, and Cr have marginal effects in dilute concentrations.…”

Effects of Alloying Atoms on Antiphase Boundary Energy and Yield Stress Anomaly of L12 Intermetallics: First-Principles Study

“…where 110 is the Burgers vector of superdislocations in {111} and {010} planes which will be dissociated into two 110 /2 partials with an APB between them [19][20][21][22][23]. There may be other dissociation types like CSF (complex stacking fault) and SISF (superlattice intrinsic stacking fault).…”