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Turnbull Lecturer Award

The Turnbull Lecturer Award recognizes the career of a scientist who has made outstanding contributions to understanding materials phenomena and properties through research, writing, and lecturing, as exemplified by David Turnbull. The Turnbull Lecturer Award is presented to David N. Seidman of Northwestern University “for research that has made major contributions to our understanding of point defects and the role they play in radiation damage and phase transformations; unique studies of interfacial segregation; and especially for the development and fruitful use of atom-probe spectrometry; for numerous seminal publications, and excellence in education/training students and colleagues in the laboratory, classroom, and conferences.”

David N. Seidman Northwestern University Talk Presentation: On the Genesis of Nuclei and Phase Decomposition on an Atomic Scale Wednesday, December 3, 5:05 pm Room 210, Hynes Convention Center

David N. Seidman received his Ph.D. degree from University of Illinois at Urbana-Champaign and his B.S. and M.S. degrees from New York University. He is currently a Walter P. Murphy Professor of Materials Science and Engineering at Northwestern University, Evanston, Illinois; prior to that he was a Professor of Materials Science and Engineering at Cornell University, Ithaca, New York. At Cornell, he went from being a postdoctoral student in 1965, with Robert Balluffi, to becoming a full professor in 1976. He started his research program, as an assistant professor at Cornell, by establishing a research group to utilize field-ion microscopy (FIM) and atom-probe FIM to study the fundamental properties of point defects (vacancies and self-interstitial atoms) in metals, alloys, and ordered phases using a highly scientific and quantitative approach to elucidate ultimately atomistic mechanisms for different physical phenomena. The point defects were created by either quenching or irradiating material. This research program included a wide range of subjects, including: vacancies in quenched metals; radiation damage (Frenkel pairs and displacement cascades) in metals, alloys, and ordered phases; diffusivities of self-interstitial atoms at cryogenic temperatures in irradiated metals and ordered structures; and atomistic structures of displacement cascades as studied by FIM. He and his students also studied the basic physics of FIM and developed atom-probe FIM as a highly quantitative instrument for studying the chemical effects associated with point and planar defects, radiation damage in metals and alloys, diffusive properties of helium and hydrogen in metals, and radiation-induced precipitation in neutron-irradiated alloys. At Cornell, he commenced studies of interfacial segregation by studying segregation at stacking faults, the simplest of all planar imperfections, in Co-Nb and Co-Fe alloys, which was the precursor to a research program on segregation phenomena that he developed after arriving at Northwestern University.

When he commenced doing research at Northwestern in September 1985, he focused on studying interfacial segregation phenomena at grain boundaries (GBs) and developed a unique combined atom-probe FIM and transmission electron microscopy (TEM) approach to study segregation, as measured by determining Gibbsian interfacial excesses with subnanoscale spatial resolution, as a function of the five macroscopic degrees (DOFs) of a GB, thereby exploring GB phase space and demonstrating that Gibbsian segregation excesses depend on the atomistic structure of GBs. In parallel, he also started performing Metropolis algorithm Monte Carlo studies of GB segregation in binary alloys, using embedded atom method potentials, in GB phase space in a systematic fashion, thereby demonstrating the importance of not only the macroscopic DOFs but also the microscopic DOFs, and therefore establishing firmly the quantitative basis for the concept of GB phase space. The research on GB segregation was extended to studies of heterophase segregation; the latter were produced by internal oxidation of ternary metallic alloys, which resulted in metal oxide/metal interfaces with segregating solute atoms at their interfaces. The Gibbsian interfacial excesses were quantitatively determined using an atom-probe FIM. In parallel with the experimental program on segregation at metal oxide/metal interfaces, extensive atomistic simulations were performed in cooperation with Roy Benedek, Argonne National Laboratory.

Seidman then focused his efforts on understanding phase decomposition in model ternary, quaternary, quinary, and sexinary nickel-based superalloys, which were studied initially using an early version of a 3-D tomographic atom-probe, and subsequently a state-of-the art 3-D local-electrode atom-probe (LEAP) tomograph, along with scanning electron microscopy and TEM. This research emphasized following the temporal evolution of the chemistry of gamma prime precipitates in a nickel matrix, where almost all the relevant physical quantities were determined experimentally and analyzed in terms of mean-field theory models. In parallel with the experimental program, lattice kinetic Monte Carlo simulations were performed and compared in great detail, on the same length scale, to the experimental results, thereby establishing atomistic mechanisms for phase decomposition. Additionally, first principles calculations were performed to understand the physical reasons behind the partitioning behavior of solute atoms between phases. Starting in 1999, and continuing to this day, he commenced a research program with his colleague David Dunand to study and develop creep-resistant Al-Sc- and Al-Me-based alloys for use at elevated temperatures (≥0.5 T_mp), with an emphasis on their creep resistance. In parallel, the microstructural evolution of these alloys was studied employing 3-D atom-probe tomography and TEM, which enabled modeling of their mechanical properties. Then, with Morris Fine, he turned his attention to Fe-based alloys that are strengthened by copper and metal carbide precipitates. The temporal evolution of the copper and metal carbide precipitates were studied employing 3-D atom-probe tomography and the results correlated with their mechanical properties. Additionally, he applied 3-D atom-probe tomography, in conjunction with first-principles calculations, to understand the atomistics of reactions between Ni-Pd and Ni-Pt alloys with silicon, as well as developing methodologies for ultimately studying individual electronic devices by 3-D atom-probe tomography.

Seidman is a Fellow of the American Physical Society, ASM International, and TMS (Minerals•Metals•Materials). He is a recipient of an Albert Sauveur Achievement Award (ASM International), a Max Planck Research Prize of the Max-Planck-Gesellschaft and Alexander Von Humboldt Stiftung awarded, jointly with the late Prof. Dr. Peter Haasen, an Alexander Von Humboldt Stiftung Prize, a John Simon Guggenheim Memorial Foundation Fellow (1980-1981 and 1972-1973), and chair of a Physical Metallurgy Gordon Conference (1982).  A MITRE evaluative study of Materials Research Laboratory Programs (MTR 7764) rated his research program for the years 1968-1977 among the top 20 most highly rated major achievements sponsored by the National Science Foundation in the area of materials science.  He is also the recipient of a Robert Lansing Hardy Gold Medal, 1966 [TMS (Minerals•Metals•Materials)]. He was a visiting professor at Technion, Tel-Aviv University, Hebrew University, Centre d'Etude Nucléaires de Grenoble, Centre National d'Etudes des Telecommunication, Meylan, Institut fuer Metallphysik der Universitaet Göttingen, Göttingen, and Centre d’Etudes Nucléaires de Saclay. He was also editor-in-chief, special editions editor, and a member of the editorial board of Interface Science (1993-2004), a member of the editorial board of Journal of Materials Science (2002-2004), was past President of the International Field-Emission Society, 2000-2002, and is currently a member of the editorial board of MRS Bulletin, 2007-present. In February 2009, he will be honored at a special symposium of the TMS (Minerals•Metals•Materials) Meeting in San Francisco.

Abstract

In David Turnbull’s list of publications, there are 53 articles listed under the rubric “nucleation,” starting in 1948 and ending in 1998, which constitutes a fifty year span of theoretical and experimental research on this fundamental aspect of phase changes [1] in the condensed state of matter. The experimental article by Servi and Turnbull on nucleation of cobalt-rich precipitates in the copper-cobalt system [2], using resistivity measurements and transmission electron microcopy, has had a major and lasting influence on studies of decomposition of metallic solid-solutions into two phases, a matrix phase and precipitates. Nucleation of precipitates followed in parallel or sequentially by their growth and coarsening, is a complex basic scientific subject [3,4,5] as well as being technologically highly relevant because of the essential roles played by structural metallic alloys at elevated temperatures in our civilization. [6] And, therefore, in view of Turnbull’s many seminal contributions to phase decomposition it is fitting that this presentation focuses on nucleation, growth and coarsening of precipitates as studied on different length scales, from the atomic scale on up, employing atom-probe tomography (APT) [7,8,9], scanning electron microscopy, transmission electron microscopy, and lattice kinetic Monte Carlo simulations [10,11,12], which constitutes a unique and multipronged approach for studying phase decomposition in concentrated multicomponent alloys. In this talk, the focus is on the use of this approach to study model nickel-based superalloys, ternary, quaternary, quinary, or sexinary alloys, a step towards the complexity of commercial alloys that contain 10 or more elements. I will show, using primarily atom-probe tomography in parallel with lattice kinetic Monte Carlo simulations, that it is possible to follow the genesis of a nucleus employing partial radial distribution-functions in direct space of Ni-Al-Cr alloys, followed by the direct observations of precipitates utilizing iso-concentration surfaces. [13] For example, using a Ni-5.2 Al-14.2 Cr (at.%) alloy, aged at 873 K, we detected g' (L12)-precipitates with a cut-off radius of ca. 0.45 nm, which corresponds to about 33 atoms. [14] While the experimental partial radial distributions, prior to the direct observation of g' (L12)-precipitates, provide evidence for clustering of atoms at an aging time of 120 seconds. [15] For this Ni-Al-Cr alloy, APT allows one to measure the temporal dependencies for following quantities for individual detected precipitates: (a) mean radius; (b) number density; (3) chemical compositions of the precipitates and the matrix and hence the chemical supersaturations in both phases; and (4) concentration profiles within the precipitates and the matrix with a spatial resolution of ca. 0.2 nm. All this information is then compared in great detail with the lattice kinetic Monte Carlo simulation results to unravel atomistic mechanisms for the experimental APT measurements. For instance, we are able to prove that the coagulation and coalescence of the g' (L12)-precipitates, in Ni-Al-Cr alloys aged at 873 K, is controlled by the long-range, out to fourth nearest-neighbor, vacancy-solute binding energy, which affects the correlated diffusion of the alloy’s constituents. And additionally to demonstrate that the shapes of the experimental concentration profiles are due to kinetic effects. Taken in concert, all this information leads to a portrait that contains a deeper physical understanding of phase decomposition in a concentrated multicomponent alloy than has heretofore been possible.

[1] D. Turnbull, “Phase Changes,” in Solid State Physics: Advances in Research and Applications, Edited by F. Seitz and D. Turnbull (Academic Press, New York 1957), Vol. 3., pp. 225-306

[2] I. S. Servi and D. Turnbull, “Thermodynamics and Kinetics of Precipitation in the Copper-Cobalt System,” Acta Metall., 14, 161-169 (1966).

[3] G. Martin, “The Theories of Unmixing Kinetics of Solid Solutions” in Solid State Phase Transformations in Metals and Alloys (Les Editions de Physique, Orsay, France, 1978), pp. 337-406.

[4] R. Wagner, R. Kampmann, and P. W. Voorhees, “Homogeneous Second Phase Precipitation” in Phase Transformations in Materials, edited by G. Kostorz (Wiley-VCH, Weinheim, 2001), pp. 309-407.

[5] R. W. Balluffi, S. M. Allen, and W. C. Carter, Kinetics of Materials (John Wiley & Sons, Hoboken, New Jersey, 2005), Chapts. 15, 17 to 21.

[6] R. C. Reed, Superalloys: Fundamentals and Applications (Cambridge University Press, Cambridge, UK, 2006).

[7] D. N. Seidman, “Three-Dimensional Atom-Probe Tomography: Advances and Applications,” Annual Review of Materials Research 37, 127-158 (2007).

[8] D. N. Seidman, “From Field-ion Microscopy of Single Atoms to Atom-Probe Tomography: A Journey,” Rev. Sci. Instrum. 78, 030901 (2007).

[9] T. F. Kelly and M. K. Miller, “Atom-Probe Tomography: An Invited Review Article,” Rev. Sci. Instrum. 78, 031101 (2007).

[10] C. Pareige, F. Soisson, G. Martin, and D. Blavette, “Ordering and Phase separation in Ni-Cr-Al: Monte Carlo Simulations vs. Three-Dimensional Atom Probe,” Acta Mater. 47, 1889-1899 (1999).

[11]C. K. Sudbrack, K. E. Yoon, Z. Mao, R. D. Noebe, D. Isheim, and D. N. Seidman, “Temporal Evolution of Nanostructures in a Model Nickel-Base Superalloy: Experiments and Simulations,” in Electron Microscopy: Its Role in Materials Research – The Mike Meshii Symposium, Edited by J.R. Weertman, M. E. Fine, K. T. Faber, W. King and P. Liaw (TMS (The Minerals, Metals & Materials Society), Warrendale, PA, 2003), pp. 43-50.

[12] Z. Mao, C. K. Sudbrack, K. E. Yoon, G. Martin, and D. N. Seidman, “The Mechanism of Morphogenesis in a Phase Separating Concentrated Multi-Component Alloy.” Nature Materials 6, 210-216 (2007).

[13] O. C. Hellman, J. A. Vandenbroucke, J. Rüsing, D. Isheim, and D. N. Seidman, “Analysis of Three-Dimensional Atom-Probe Data by the Proximity Histogram,” Microscopy and Microanalysis 6, 437-444 (2000).

[14] C. K. Sudbrack, K. E. Yoon, R. D. Noebe and D. N. Seidman, “Temporal Evolution of the Nanostructure and Phase Compositions in a Model Ni-Al-Cr Superalloy,” Acta Mater. 54, 3199-3210 (2006).

[15] C. K. Sudbrack, R. D. Noebe, and D. N. Seidman, “Direct Observations of Nucleation in a Non-dilute Multicomponent Alloy,” Phys. Rev. B 73, 212101 (2006).