Publication Date:
2019
Description:
〈p〉Publication date: Available online 28 March 2019〈/p〉
〈p〉〈b〉Source:〈/b〉 Acta Materialia〈/p〉
〈p〉Author(s): Elizaveta Y. Plotnikov, Zugang Mao, Sung-Il Baik, Mehmet Yildirim, Yongsheng Li, Daniel Cecchetti, Ronald D. Noebe, Georges Martin, David N. Seidman〈/p〉
〈div xml:lang="en"〉
〈h5〉Abstract〈/h5〉
〈div〉〈p〉The temporal evolution of ordered γ’(L1〈sub〉2〈/sub〉)-precipitates precipitating in a disordered γ(f.c.c.) matrix is studied in extensive detail for a Ni-12.5 Al at.% alloy aged at 823 K (550 〈sup〉o〈/sup〉C), for times ranging from 0.08 to 4096 h. Three-dimensional atom-probe tomography (3-D APT) results are compared to monovacancy-mediated lattice-kinetic Monte Carlo (LKMC〈sub〉1〈/sub〉) simulations on a rigid lattice, which include monovacancy-solute binding energies through 4〈sup〉th〈/sup〉 nearest-neighbor distances, for the same mean composition and aging temperature. The temporal evolution of the measured values of the mean radius, 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"〉〈mrow〉〈mrow〉〈mo〉〈〈/mo〉〈mrow〉〈mi〉R〈/mi〉〈mrow〉〈mo〉(〈/mo〉〈mi〉t〈/mi〉〈mo〉)〈/mo〉〈/mrow〉〈/mrow〉〈mo〉〉〈/mo〉〈/mrow〉〈/mrow〉〈/math〉, number density, aluminum supersaturations, and volume fraction of the γ’(L1〈sub〉2〈/sub〉)-precipitates are compared to the predictions of a modified version of the Lifshitz-Slyozov diffusion-limited coarsening model due to Calderon, Voorhees et al. The resulting experimental rate constants are used to calculate the Gibbs interfacial free-energy between the γ(f.c.c.)- and γ’(L1〈sub〉2〈/sub〉)-phases, which enter the model〈em〉,〈/em〉 using data from two thermodynamic databases, and its value is compared to all exiting values. The diffusion coefficient for coarsening is calculated utilizing the same rate-constants and compared to all archival diffusivities, 〈em〉not determined from coarsening experiments, and it is demonstrated to be the inter-diffusivity,〈/em〉 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.gif" overflow="scroll"〉〈mrow〉〈mover accent="true"〉〈mi〉D〈/mi〉〈mo〉˜〈/mo〉〈/mover〉〈/mrow〉〈/math〉〈em〉, of Ni and Al.〈/em〉 The monovacancy-mediated LKMC〈sub〉1〈/sub〉 simulation results are in good agreement with our 3-D APT data. The compositional interfacial width, for the {100}-interface, between the γ(f.c.c.)- and γ’(L1〈sub〉2〈/sub〉)-phases, decreases continuously with increasing aging time and 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"〉〈mrow〉〈mrow〉〈mo〉〈〈/mo〉〈mrow〉〈mi〉R〈/mi〉〈mrow〉〈mo〉(〈/mo〉〈mi〉t〈/mi〉〈mo〉)〈/mo〉〈/mrow〉〈/mrow〉〈mo〉〉〈/mo〉〈/mrow〉〈/mrow〉〈/math〉, both for the 3-D APT results and the monovacancy-mediated LKMC〈sub〉1〈/sub〉 simulations, in disagreement with an 〈em〉ansatz〈/em〉 intrinsic to the trans-interface diffusion-controlled coarsening model, which assumes the exact opposite trend for binary alloys.〈/p〉〈/div〉
〈/div〉
〈h5〉Graphical abstract〈/h5〉
〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359645419301594-fx1.jpg" width="255" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉
Print ISSN:
1359-6454
Electronic ISSN:
1873-2453
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Permalink