Purveyors of Processing Science and ICME: A SMD Symposium to Honor the Many Contributions of Taylan Altan, Wei Tsu Wu, Soo-Ik Oh, and Lee Semiatin: Superalloys
Sponsored by: TMS Structural Materials Division, TMS: Shaping and Forming Committee, TMS: Titanium Committee
Program Organizers: Adam Pilchak, Pratt & Whitney; Ayman Salem, MRL Materials Resources LLC; Viola Acoff, University of Mississippi; Nathan Levkulich, UES; Michael Glavicic, Rolls-Royce; Yufeng Zheng, University of North Texas; John Joyce-Rotella, Air Force Research Laboratory
Monday 8:00 AM
February 24, 2020
Room: 30E
Location: San Diego Convention Ctr
Session Chair: Tresa Pollock, University of California - Santa Barbara; Paul Jablonski, National Energy Technology Laboratory
8:00 AM Introductory Comments Adam L. Pilchak
8:10 AM Invited
Directional Recrystallization Processing: Ian Baker1; 1Dartmouth College
The microstructures of directionally-recrystallized, cold-rolled polycrystalline nickel have been investigated using both EBSPs on a SEM and optical microscopy. The effects of the process parameters (hot zone velocity, hot zone temperature and temperature gradient ahead of the hot zone) and microstructural parameters (solute, particles) on the microstructure produced by directional annealing will be outlined. Columnar grains and single crystals could be produced by secondary recrystallization following primary recrystallization over a wide range of hot zone velocities, but only at high temperature (≥1100K) with a large temperature gradient. The effects of solutes and particles was to move the processing window to higher temperatures and lower hot zone velocities. The results of simulations of directional recrystallization using a front-tracking model will also be presented for both particle-free and particle-containing material, and compared to experimental observations. This research is currently supported by the U.S. Army Research Office grant W911NF-16-1-0367.
8:40 AM Invited
The Operation of a Research Scale Esr Furnace and its Impact on Trace Elements: Paul Jablonski1; Martin Detrois1; 1National Energy Technology Laboratory
Vacuum induction melting (VIM), electro-slag remelting (ESR) and vacuum arc remelting (VAR) are all techniques used to make high quality ingots of complex chemistries. In some cases, all three are used, e.g., alloys for aerospace applications and increasingly those for fossil power applications under extreme conditions. As such, research on alloys of this class require access to a variety of melting capabilities. In this report we discuss our recent experiences with a laboratory scale (200mm/200kg) combination VAR/ESR furnace. The focus will be on the ESR operation, and its use for control of unwanted elements. Two master alloys are considered: Ni-25Cr and Ni-30Co-30Cr, processed through a combination of VIM and ESR. The role of the alloy additions in modifying the melting characteristics lowering the tramp element content and residual inclusions were determined computationally and confirmed experimentally. The usefulness of these master alloys as experimental remelt stock will also be discussed.
9:10 AM Invited
Microstructure Control of Nickel based Superalloy Forgings: a Focus onto Post-dynamic Evolutions: Nathalie Bozzolo1; Marc Bernacki1; 1MINES ParisTech
Microstructure evolution during forging is often considered to be a dynamic process, and described with regards to the applied thermomechanical processing parameters. When dealing with large components, cooling after forging is necessarily rather slow, and allows for post-dynamic evolutions which can drastically change the microstructure.Mechanisms and kinetics of post-dynamic evolutions are highly sensitive to temperature of course, but also to the formerly applied strain rate, and to the recrystallization fraction achieved dynamically (and thus to the strain level). This all will be discussed based on finely controlled experiments showing i) that post-dynamic recrystallization can be an extremely fast process, and ii) that it can be the only remaining recrystallization mechanism when increasing strain rate. The possibility of simulating both dynamic and post-dynamic evolutions using full field finite element models will be addressed as well.
9:40 AM Break
10:00 AM Invited
Annealing Twins in Wrought Polycrystalline Superalloys: Marie Charpagne1; J.C. Stinville1; Will Lenthe1; McLean Echlin1; Tresa Pollock1; 1University of California, Santa Barbara
The properties of wrought polycrystalline superalloys are sensitive to the final structure that develops across the thermomechanical processing path. Fatigue, one of the most critical properties, is influenced by the presence of annealing twins under conditions where extrinsic defects do not dominate cyclic behavior. While annealing twins develop during the final recrystallization and grain growth processes, the details of the mechanisms that result in their formation are still not completely understood. Three-dimensional multimodal datasets collected by TriBeam tomography enable the network structure of twins to be studied. The character of large twin-related domains that form as a result of recrystallization will be discussed, along with the role of precipitates present during subsolvus processing. The important role of the network structure for fatigue crack initiation and propagation will be addressed.
10:30 AM Invited
Towards Rapid Throughout Measurement of Grain Boundary Properties: Jin Zhang1; Peter Voorhees1; Henning Poulsen2; 1Northwestern University; 2Technical University of Denmark
The materials design process rests on a foundation of data. Unfortunately, there are many parameters that are central to a design effort and are challenging to measure, such as grain boundary energies and mobilities. A rapid throughput method is developed to measure grain boundary properties by comparing the evolution of experimentally determined 3D grain structures to that derived from phase field simulations. Grain evolution in pure iron is determined in three dimensions and as a function of time using diffraction contrast tomography. Using a time step from these data as an initial condition in a phase-field simulation, the computed grain structure is compared to that measured experimentally at a later time. An optimization technique is then used to find the reduced grain boundary mobilities of many thousands of grains that yields the best match of the simulated microstructure. The results of this approach will be discussed.
11:00 AM Invited
Enhancing the Properties of Ni-based Superalloys via Mesoscale Engineering: Sammy Tin1; 1Illinois Institute of Technology
Superalloys are critical structural materials that ideally suited for high performance gas turbine applications due their excellent resistance to deformation and environmental degradation at elevated temperatures. Although many of the intrinsic characteristics of superalloys can be attributed to the underlying alloy chemistry, in many instances the properties of these alloys can be enhanced through mesoscale engineering or control of the grain boundary character and morphology. The emergence and acceptance of ICME design methodologies within the materials community has contributed greatly to the fundamental understanding of how microstructure evolves during thermal-mechanical processing. This talk will describe how we have applied this knowledge to develop innovative thermal-mechanical processes that can be effectively utilized to engineer the grain boundary character and morphology of Ni-base superalloys and enhance the creep and dwell fatigue performance of the material.