The effect of rhenium on the microstructure stability and γ/γ′ interfacial characteristics of Ni-based single crystal superalloys during long-term aging

Effect of the Addition of Re on the Microstructure and Phase Composition of Haynes 282: Ab Initio Modelling and Experimental Investigation of Additively Manufactured Specimens

“…The α 1 characteristic of the Ni-Re pair indicates that because of slightly positive values lower than 0.25, Ni and Re create a disordered solid solution in which the elements show little tendency to segregate.Based on the modelling results, it is suspected that Al and Re would strongly segregate from one another. Therefore, Re is not supposed to be present within an ordered gamma L1 2 Ni 3 Al structure (Figure1b), which agrees with experimental investigations of other Ni-based superalloys[9]. As shown in Figure2b, the α 1 values for the Ni-Al system were the lowest of the investigated atomic Al pairs, making this element the one most likely to exist in phases with Ni.…”

“…After a debate over the mechanisms underlying the Re effect, it was shown that the improvement in creep strain rate results directly from Re enrichment to partial dislocations, hindering their movement [ 8 ]. Besides its direct interactions with dislocations, Re significantly enhances the stability of gamma precipitates and suppresses variations in composition within the gamma matrix [ 9 ]. Re atoms, which have the lowest diffusion coefficient in Ni-based superalloys, slow down diffusion-controlled processes in the microstructure, therefore increasing its stability during exposure to high temperatures [ 4 , 9 ].…”

“…Besides its direct interactions with dislocations, Re significantly enhances the stability of gamma precipitates and suppresses variations in composition within the gamma matrix [ 9 ]. Re atoms, which have the lowest diffusion coefficient in Ni-based superalloys, slow down diffusion-controlled processes in the microstructure, therefore increasing its stability during exposure to high temperatures [ 4 , 9 ]. It has been shown that Re atoms enrich gamma dendrites in multicomponent Ni alloys [ 7 , 10 , 11 , 12 , 13 , 14 ], leading to a non-homogeneous distribution of elements between dendritic and interdendritic regions.…”

Investigation of interfacial strength in nacre-mimicking tungsten heavy alloys for nuclear fusion applications

“…This diffuse boundary region is measured to be between 1.2 and 2.9 nm in width and is theorized to be a result of the boundary approaching a state of chemical equilibrium. While the exact width of this boundary is unknown, its existence is corroborated by Monte Carlo simulation of free energy minimization in multicomponent systems 30 and has been discussed experimentally in the Au-Cu 45 , Co-Al-W 46 , 47 , and Ni-based alloys 48 , 49 . In following the classical Cahn–Hilliard approach for the equilibrium composition across the boundary in a two-phase system, a chemically diffuse boundary is energetically favorable, with steep chemical gradients, or narrow interface widths, imposing an energy penalty in the system 30 , 31 , 44 .…”

Process Optimization in Laser Welding of IN792 DS Superalloy

“…The microstructure consists of Ll 2 ordered particles of Ni 3 (Al, Ti) γ ′ phase embedded in a disordered γ phase matrix. The stability of the microstructure (γ + γ ′ ) depends on the misfit of the lattice parameters of γ and γ ′ phases, and on the reduced interface energy (20-30 mJ m −2 ) obtained through a strict control of the chemical composition and manufacturing process parameters [8][9][10][11][12]. Recently, simulations have been extensively employed to predict the microstructural features and mechanical properties of these materials after complex thermal cycles [13,14].…”