The mechanism of morphogenesis in a phase-separating concentrated multicomponent alloy

Mao, Zugang; Sudbrack, Chantal K.; Yoon, Kevin E.; Martin, G.; Seidman, David N.

doi:10.1038/nmat1845

Cited by 155 publications

(104 citation statements)

References 33 publications

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“…The experimental nanostructural temporal evolution has been reproduced with recent LKMC simulations using the same aging conditions [17]. These LKMC simulations verify that coagulation (t 6 4 h) and coalescence without significant precipitate migration is responsible for the interconnected c 0 -phase nanostructure that is observed rather than precipitate splitting, which can result from growth instabilities or elastically induced splitting [38].…”

Section: Nucleation and Growth Of The Csupporting

confidence: 59%

“…This furthermore demonstrates experimentally that an upper bound to the critical radius of nucleation is approximately 0.75 nm. Stability of the c 0 -nuclei can be assessed directly from LKMC simulations for the same aging conditions [17]. The LKMC simulations indicate that when c 0 -precipitates contain approximately 40 atoms they become resistant to dissolution, which corresponds to a critical radius of nucleation, R * , value of 0.485 nm, which is 35% smaller than our upper bound of 0.75 nm.…”

Section: Nucleation and Growth Of The Cmentioning

confidence: 81%

“…The seminal research of Schmuck et al and Pareige et al [12,13] demonstrates that experimental APT observations, in conjunction with lattice kinetic Monte Carlo (LKMC) simulations, yields a detailed atomic-scale picture of the early-stage decomposition of a model Ni-Al-Cr alloy. Applying this combined approach, our research efforts [14][15][16][17][18][19] focus on the genesis of the c 0 -phase and its nanostructural and compositional evolution in a nearly identical Ni-Al-Cr alloy, Ni-5.2 Al-14.2 Cr at.%, containing low to moderate solute supersaturations, as it decomposes isothermally at 873 K. In this article, the APT characterization of the c 0 -phase morphological development, phase composition evolution, and nanostructural evolution demonstrates that the transformation initiates by nucleation and growth and with increasing aging time enters a quasi-steady-stationary regime, where growth and coarsening are concomitantly operating. The experimental analyses presented permit the composition and radius of the critical nucleus, the equilibrium solvus-line compositions, and the three classic temporal power-law exponents for coarsening to be determined; the latter is compared to extant models of coarsening.…”

Section: Introductionmentioning

confidence: 99%

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Temporal evolution of the nanostructure and phase compositions in a model Ni–Al–Cr alloy

et al. 2006

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In a Ni-5.2 Al-14.2 Cr at.% alloy with moderate solute supersaturations and a very small c/c 0 lattice parameter misfit, the nanostructural and compositional pathways during c 0 (L1 2 ) precipitation at 873 K are investigated using atom-probe tomography, conventional transmission electron microscopy, and hardness measurements. Nucleation of high number densities (N v > 10 23 m À3 ) of solute-rich precipitates (mean radius = AERae = 0.75 nm), with a critical nucleus composition of Ni-18.3 ± 0.9 Al-9.3 ± 0.7 Cr at.%, initiates between 0.0833 and 0.167 h. With increasing aging time (a) the solute concentrations decay in spheroidal precipitates (AERae < 10 nm); (b) the observed early-stage coalescence peaks at maximum N v in coincidence with the smallest interprecipitate spacing; and (c) the reaction enters a quasi-stationary regime where growth and coarsening operate concomitantly. During this quasi-stationary regime, the c (face-centered cubic)-matrix solute supersaturations decay with a power-law dependence of about À1/3, while the dependencies of AERae and N v are 0.29 ± 0.05 and À0.64 ± 0.06 at a coarsening rate slower than model predications. Coarsening models allow both equilibrium phase compositions to be determined from the compositional measurements. The observed early-stage coalescence is discussed in further detail.

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Section: Nucleation and Growth Of The Csupporting

confidence: 59%

Section: Nucleation and Growth Of The Cmentioning

confidence: 81%

Section: Introductionmentioning

confidence: 99%

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Temporal evolution of the nanostructure and phase compositions in a model Ni–Al–Cr alloy

et al. 2006

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“…Coarsening and coalescence of γ′ precipitates, through application of the LSW theory and particle agglomeration mechanism have been studied in several research works [22,23].…”

Section: Introductionmentioning

confidence: 99%

Coarsening and dissolution of γ′ precipitates during solution treatment of AD730™ Ni-based superalloy: Mechanisms and kinetics models

Masoumi

Jahazi

Shahriari

et al. 2016

Journal of Alloys and Compounds

145

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The kinetics of γ′ size and volume fraction changes during solution treatment of the advanced Ni-based superalloy, AD730 TM are determined and the underlying mechanisms are investigated.High resolution Differential Thermal Analysis (DTA) and thermodynamic modeling were used to design and perform solution heat treatment experiments. Semi-analytical models are developed to describe the dissolution and coarsening processes. The results from the proposed models, supported by electron microscopy observations, indicate that coarsening occurs before complete dissolution takes place. Agglomeration is shown to be the governing coarsening mechanism for this alloy after calculation of the coefficients for both the Ostwald ripening and agglomeration mechanisms. Electron microscopy observations revealed that the early stages of agglomeration occur by neck formation between two neighboring particles. The splitting of γ′ particles was identified as one of the main dissolution mechanisms. Based on the obtained results, a dissolution kinetics model is proposed to quantify the volume fraction of dissolved γ′ particles and estimate the activation energy of this process for AD730 TM . A coarsening model based on the time-temperature dependence of the γ′ coarsening rate coefficient is also proposed taking the concentration of elements, γ′ volume fraction and the temperature into consideration. Based on this model, a method is developed to predict γ′ size evolution during aging heat treatment process and an optimum heat treatment to reach the desired γ′ distribution is proposed.The validity and accuracy of the proposed models were verified by carrying out different heat treatment experiments.

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“…Another interesting point that arises from analyzing such diagrams is how APT is now used to complement other techniques: terms related to differential scanning calorimetry, scanning & transmission electron microscopy, X-ray diffraction and small-angle scattering, as well as atomistic simulations, such as (kinetic) Monte Carlo, molecular dynamics or density functional theory, can all be found. This highlights how APT has progressively and increasingly been integrated into correlative approaches (De Geuser et al, 2014;Gault et al, 2012; Herbig et al, 2015; Krug et al, 2014;Larson et al, 2009;Mao et al, 2007), in order to best exploit its strengths. …”

mentioning

confidence: 99%

A Brief Overview of Atom Probe Tomography Research

Gault

2016

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Atom probe tomography (APT) has been fast rising in prominence over the past decade as a key tool for nanoscale analytical characterization of a range of materials systems. APT provides three-dimensional mapping of the atom distribution in a small volume of solid material. The technique has evolved, with the incorporation of laser pulsing capabilities, and, combined with progress in specimen preparation, APT is now able to analyse a very range of materials, beyond metals and alloys that used to be its core applications. The present article aims to provide an overview of the technique, providing a brief historical perspective, discussing recent progress leading to the state-of-the-art, some perspectives on its evolution, with targeted examples of applications.Key Words: Atom probe tomography, Field evaporation, Materials characterization, Microscopy, Nanoscale Gault B 118The specimen is progressively destroyed, almost atom-byatom, and the atom probe microscope collects the timeof-flight and impact position of each ion. Processing of the data translates the time-of-flight into a mass-to-charge ratio, and the position is used to build a tomographic, atomically resolved image of the evaporated volume (Bas et al., 1995;Larson et al., 2013), represented as a point-cloud where every point is an atom that has been elementally identified and repositioned with a high degree of precision (Gault et al., 2010b). INSTRUMENTAL DESIGNEarly designs of the technique, usually referred to as atomprobe field ion microscopes or one-dimensional (1D) atom probe (Miller, 2000;Müller et al., 1968), had a very narrow field-of-view and really only provided linear compositional measurement in the depth of the sample, within a region of interest located by field-ion microscopy (Brenner & Goodman, 1971). APT was truly enabled by the implementation of position-sensitive, time-resolved particle detectors by Cerezo et al. (1988) followed by Blavette et al. (1993), and modern microscopes are equipped with delayline detectors (Da Costa et al., 2005; Jagutzki et al., 2002). The incorporation of micro-channel plates (MCPs) in the design of such detectors, to convert the impact of a single-ion into a cascade of up to millions of electrons, limits the efficiency approximately to the open area of the MCPs, so between 50%~80%. The MCPs are operated in saturated mode, which ensures almost no mass or atomic number sensitivity for ions in the range of 2~3 kV up to 15~20 kV up to several hundreds of Da, and the loss of ions is therefore nonspecific and assumed to be random and hence not affecting the technique's capacity to precisely measure the elemental composition. In order to increase the mass resolution of the technique, limited by the energy spread of the emitted ions, reflectron-lenses were fitted onto atom probes (Bémont et al., 2003;Cerezo et al., 1998;Panayi, 2006). A reflectron acts as an electrostatic mirror: ions penetrate inside a region containing a well-defined electric field in which ions are progressively slowed down until they are returne...

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The mechanism of morphogenesis in a phase-separating concentrated multicomponent alloy

Cited by 155 publications

References 33 publications

Temporal evolution of the nanostructure and phase compositions in a model Ni–Al–Cr alloy

Temporal evolution of the nanostructure and phase compositions in a model Ni–Al–Cr alloy

Coarsening and dissolution of γ′ precipitates during solution treatment of AD730™ Ni-based superalloy: Mechanisms and kinetics models

A Brief Overview of Atom Probe Tomography Research

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