Solute segregation and deviation from bulk thermodynamics at nanoscale crystalline defects

Abstract

Atomistic processes governing the high-temperature strength of structural materials were accurately characterized and modeled.

A defect-resistant Co–Ni superalloy for 3D printing

“…CASM includes cluster expansions for configurational disorder in multi-component solids and lattice-dynamical effective Hamiltonians for vibrational degrees of freedom involved in structural phase transitions. CASM was used to assess the intrinsic thermodynamic stability of the L1 2 phase at elevated temperatures, to calculate the ternary Co-Al-W phase diagram and to assess the finite temperature fault energies and the driving forces for segregation at planar faults [45][46][47] .…”

Correlative Microscopy—Novel Methods and Their Applications to Explore 3D Chemistry and Structure of Nanoscale Lattice Defects: A Case Study in Superalloys

“…30,31 Figure 3c shows a high-resolution STEM image revealing the D0 19 ordered structure of the fault plane surrounded by the L1 2 c¢ precipitate. 31,32 A missing A-type plane as visible in Fig. 3d reveals that this is an intrinsic SF.…”

Understanding creep of a single-crystalline Co-Al-W-Ta superalloy by studying the deformation mechanism, segregation tendency and stacking fault energy

“…The main difference between Ni-and Co-base superalloys regarding the double minimum creep behavior at high temperatures is that  precipitates are cut by a/2<110> dislocation pairs in Nibase alloys [20,23,24] while the precipitate shearing in Co-and CoNi-base alloys is accompanied by the formation of extended superlattice stacking faults (SFs) [7,9,10,[16][17][18][25][26][27][28]. Stacking faults are formed due to a thermally activated reaction of a/2<110>{111} dislocations, which results in a leading partial dislocation of a/3<112> type creating a superlattice intrinsic stacking fault (SISF) and a trailing partial dislocation of a/6<112> type that remains at the / interface.…”