Microstructural Templates Consisting of Isostructural Ordered Precipitate / Disordered Matrix Combinations: Microstructural Evolution and Properties: Session III
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Phase Transformations Committee
Program Organizers: Rajarshi Banerjee, University of North Texas; Eric Lass, University of Tennessee-Knoxville; Bharat Gwalani, North Carolina State Universtiy; Jonah Klemm-Toole, Colorado School of Mines; Jessica Krogstad, University of Illinois at Urbana-Champaign; Ashley Paz Y Puente, University of Cincinnati; Keith Knipling, Naval Research Laboratory; Matthew Steiner, University of Cincinnati
Wednesday 2:00 PM
March 2, 2022
Room: 254A
Location: Anaheim Convention Center
Session Chair: Ashley Puente, University of Cincinnati; Keith Knipling, Naval Research Laboratory
2:00 PM Introductory Comments
2:05 PM Invited
Comparison of γ' and B2 Precipitates and Their Influence on the Mechanical Behavior of FeNiCoAl-based High-entropy Alloys: Cheng Zhang1; Benjamin MacDonald1; Mingjie Xu1; Enrique Lavernia1; 1University of California, Irvine
As one of the most popular face-centered cubic high-entropy alloys (HEAs), FeNiCoAl-based HEAs exhibit highly tunable properties, such as an excellent strength-ductility synergy at ambient or cryogenic temperatures. Up to date, depending on the Al concentration, some studies have addressed the influence of the L12 γ’ (including Ni3Al and Ni3Ti) nanoscale particles, while other studies have focused on the effect of the B2 (NiAl) precipitates. In this talk, we will compare the influence of γ’ and B2 precipitates on the mechanical behavior of FeNiCoAl-based HEAs. The thermal stability of these two precipitates at elevated temperatures will also be addressed. In addition, some new nanoscale particles inside these initial precipitates at specific temperatures will be shown, which effectively lead to the formation of a hierarchical structure. Finally, a strategy involving the use of γ’ and B2 to tailor the microstructure of FeNiCoAl-based HEAs for additional strengthening will be described.
2:35 PM Invited
Understanding the Role of Chemistry on Planar Fault Energies in A3B Compositions: K V Vamsi1; Tresa Pollock1; 1University of California, Santa Barbara
Superalloys are one such class of alloys where the L12 and D022 (A3B type) ordered precipitates provide significant strengthening by impeding the motion of the dislocations through the precipitates. The presence of these ordered precipitates results in a variety of deformation modes involving various superlattice stacking faults. Though the research in this field has advanced over a few decades, the effect of chemistry on the role of planar fault energies is not well understood. Recent advancements in emerging high-entropy alloys (HEAs) have opened up new avenues for exploring novel precipitate strengthened multicomponent alloys, and challenges in estimating fault energies in multicomponent compositions will be highlighted. Modeling planar fault energies in L12 and D022 structures with state-of-the-art methods will be reviewed. Deriving planar fault energies using a novel diffuse multi-layer fault model for CoNi-based precipitate compositions will be presented, and implications on the alloy design will be discussed.
3:05 PM Invited
Optimizing Composition and Microstructure in Compositionally Complex Alloys Possessing bcc and B2 Mixtures: Zachary Kloenne1; Brian Welk1; Kamalnath Kadirvel1; G. Babu Viswanathan1; Jean-Philippe Cousinie1; Yunzhi Wang1; Hamish Fraser1; 1The Ohio State University
In several compositionally complex alloys (CCA), a microstructure is exhibited that includes mixtures of a bcc phase and the ordered B2 compound, and which often resembles that of Ni-base superalloys. The present study has involved an assessment of whether these new alloys offer a promise for intermediate and high temperature applications. The research has involved three aspects. In the first, the transformation pathway responsible for the development of microstructures has been determined using a combination of phase field modeling and microstructural characterization. In the second, the nature of the B2 phase has been studied, involving a determination of the site occupancy in the sub-lattices of the B2 compound, using spatially-resolved energy dispersive spectroscopy (XEDS). In the third, the nature of the interfaces between the ordered and disordered phases has been fully characterized using aberration-corrected (S)TEM, and the nature of slip transmission through these interfaces has been studied.
3:35 PM Break
3:55 PM
Precipitation of Ordered B2 Precipitates in BCC Al2.7CrMnTiV High-entropy Alloys: Keith Knipling1; Patrick Callahan1; David Beaudry1; 1Naval Research Laboratory
The microstructures formed in an Al2.7CrMnTiV high-entropy alloy are studied using a combination of atom probe tomography (APT), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and X-ray diffraction (XRD) as well as predictions from Thermo-Calc. In the as-cast state, the alloy consists of a body-centered cubic (bcc) matrix with micron-scale L10 lath-shaped precipitates, enriched in Al and Ti, that are predicted by Thermo-Calc. Additionally, coherent B2 cuboids on the order of 10 nm are formed, resembling the γ-γ' microstructure of Ni-based superalloys but in a BCC system. We study the precipitation-hardening behavior by solutionizing and aging the alloy, and measuring the mechanical properties after aging. After the solution heat treatment, the alloy is single phase BCC. The mechanical properties after aging are correlated with underlying microstructure and distribution of the ordered B2 nanoscale precipitates in the disordered BCC matrix.
4:25 PM
Bcc-Superalloys Microstructure Templates: Tungsten to Titanium to Iron: Alexander Knowles1; 1University of Birmingham
The microstructure template of a disordered matrix reinforced by ordered-intermetallic precipitates offer a potent design strategy for high temperature materials, enabling strength alongside damage tolerance, which has been central to the success of fcc Ni-superalloys. Such a strategy is equally applicable to bcc-based systems, which offer advantages of increased melting point and lower cost. However, whilst bcc-superalloys of refractory metals (RM), titanium or iron strengthened by ordered-bcc precipitates such as B2 or L21 are possible, they are yet to be a commercial reality.In this talk, opportunities for bcc-superalloys systems will be discussed, from binaries to Fe-NiAl, Cr-Ni2AlTi, Mo-NiAl, Ta-(Ti,Zr)2Al(Mo,Nb) and Nb-Pd2HfAl as well as Refractory High Entropy Superalloys. It will then discuss our latest developments in tungsten-based bcc-superalloys, beta-Ti superalloys and ferritic superalloys and give perspectives for the onward development of the bcc-superalloy concept for application in nuclear fusion, Gen-IV fission, gas turbines and concentrated solar power.
4:55 PM
The Microstructural Design and Thermomechanical Processing of Compositionally Complex Alloys: Mark Wischhusen1; Samuel Inman1; Jie Qi1; Joseph Poon1; John Scully1; Jishnu Bhattacharyya1; Alireza Zargaran2; Sean Agnew1; 1University of Virginia; 2Pohang University of Science and Technology
High entropy and compositionally complex alloys provide a large amount of flexibility in terms of component elements, but the single-phase alloys that largely populate this space are often limited in the strengthening mechanisms they have access to. Beyond solid solution strengthening and grain refinement, multi-phase alloys can be further tailored to optimize engineering properties. Alloys which have an FCC matrix phase, especially, may be optimized for strength and corrosion resistance while retaining a reasonable amount of ductility. By combining inspiration from existing multiphase alloys with corrosion resistance sensibilities, microstructure-based strain hardening models, and thermomechanical processing informed by phase stability predictions from ThermoCalc, a novel steel or other lightweight alloy strengthened by an ordered second phase may be designed which has exceptional performance in marine environments.
5:20 PM Concluding Comments