Phase Transformations and Microstructural Evolution: Superalloys and Shape Memory Alloys
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Phase Transformations Committee
Program Organizers: Mohsen Asle Zaeem, Colorado School of Mines; Ramasis Goswami, Naval Research Laboratory; Saurabh Puri, VulcanForms Inc; Eric Payton, University of Cincinnati; Megumi Kawasaki, Oregon State University; Eric Lass, University of Tennessee-Knoxville
Tuesday 2:30 PM
March 1, 2022
Room: 255B
Location: Anaheim Convention Center
Session Chair: Eric Lass, University of Tennessee-Knoxville
2:30 PM Invited
A Strategy to Optimize Local Phase Transformation Strengthening for Next Generation Superalloys: Timothy Smith1; Nikolai Zarkevich2; Ashton Egan3; Timothy Gabb1; John Lawson2; Michael Mills3; 1NASA Glenn Research Center; 2NASA Ames; 3Ohio State University
For this study, a new disk superalloy (TSNA-1) specifically designed to take advantage of strengthening atomic-scale dynamic complexions is explored. This local phase transformation (LPT) strengthening provided TSNA-1 with a 3x improvement in creep strength over similar disk superalloys and comparable strength compared to the single crystal blade alloy CMSX-4 at 760 °C. Through ultra-high-resolution chemical mapping of the stacking faults induced by creep deformation, it was discovered that the improvement in creep strength was a result of atomic-scale η (D024) and χ (D019) formation along superlattice stacking faults. To understand these results, the energy differences between the L12 and competing D024 and D019 stacking fault structures and their dependence on composition were then computed from first principles using density functional theory. Findings from this study can help guide researchers to further optimize the LPT strengthening mechanism for future alloy development.
3:00 PM
An Investigation into the Effect of Primary Gamma Prime Stimulated Metadynamic Recrystallization on Supersolvus Grain Sizes in Ni Superalloy LSHR: Eric Payton1; Jared Shank2; Kayla Evans3; Denielle Ricciardi2; Victoria Miller4; 1Air Force Research Laboratory; 2UES, Inc; 3Wright State University; 4University of Florida
Recent work has generated considerable interest in some peculiarities in the recrystallization behavior of Ni superalloys, in particular the heteroepitaxial recrystallization mechanism and evidence of primary gamma prime reducing the barrier to nucleation during recrystallization. Grain size control in Ni superalloys is critical to their performance in turbine engine applications, and different grain sizes are optimal for fatigue resistance in the bore and creep resistance at the rim. An improved understanding of the role of dynamic and metadynamic recrystallization on grain size is needed to advance models of microstructure evolution during processing of these alloys. In this work, we systematically vary how the primary gamma prime phase affects recrystallization in the Ni superalloy LSHR through different subsolvus soak time, strain rate, and strain levels, then investigate how these variations in subsolvus dynamic and metadynamic recrystallization affect the matrix grain size after supersolvus heat treatment.
3:20 PM
Lattice Correspondences in Martensitic Transformation and Twinning in NiTi Shape Memory Alloy: Bin Li1; 1University of Nevada, Reno
The pioneers of physical metallurgy realized that in martensitic transformation and deformation twinning, a one-to-one lattice correspondence must exist between the parent and the product lattice. Thus, by analyzing the lattice correspondence, we can resolve the mechanisms for phase transformation and deformation twinning with clarity. The shape memory effect in NiTi alloy involves both martensitic transformation and mechanical twinning, and these processes must be reversible, which is necessary for shape memory effect. In this work, lattice transformation from ordered B2 austenite to monoclinic B19’ martensite, and lattice transformation for deformation twinning in B19’ martensite are analyzed, based on the results obtained from atomistic simulations. The results show that during martensitic transformation and twinning, only atomic shuffles are involved. These dislocation-free lattice transformations ensure both martensitic transformation and twinning are all reversible.
3:40 PM
Phase-field Modeling and Design of Elastocaloric Effect in Shape Memory Alloys and Composites: Cheikh Cisse1; Mohsen Asle Zaeem1; 1Colorado School of Mines
We present the most complete elastoplastic phase-field model for shape memory alloys. It is fully thermo-mechanically coupled via the consideration of latent heat and temperature-dependent energy coefficients, and it can quantitively predict the shape memory effect, pseudoelasticity and thermomechanical training in polycrystalline shape memory alloys. Using this model, we investigate the microstructural change that are responsible for the elastocaloric properties of bulk shape memory alloys such as CulAlBe. It helps understand the relation between the reversible phase transition and the temperature variation during pseudoelasitc cycle, the plastic-induced functional fatigue, and the effects of loading conditions. We also use this model as a design tool to optimize and control the coefficient of performance of NiTi-based shape memory composites via the microarchitecture of the intermetallic phase (composition, volume fraction, shape and aspect ratio).
4:00 PM Break
4:20 PM
The Effect of Precipitate Size on the Thermo-mechanical Properties of Ni-Ti-Hf-Al Shape Memory Alloys: Ching-Chien Chen1; Shivam Tripathi1; Alexandra Loaiza1; David Bahr1; Alejandro Strachan1; Michael Titus1; 1Purdue University
The presence of coherent precipitates can significantly tune the transformation behavior in martensitic materials and can result in unprecedented thermomechanical properties. The addition of Al as an alloying element to high-temperature Ni-Ti-Hf-based shape memory alloys has been shown to result in the formation of coherent Ni2TiAl Heusler precipitates, which could lead to unique properties. In this study, we systematically investigate the role of Ni2TiAl Heusler precipitates on the thermo-mechanical properties of Ni-Ti-Hf-Al based shape memory alloys. A combination of calorimetry, nanoindentation, and high-resolution transmission electron microscopy was used to characterize the shape memory alloy behavior. We find that the precipitates initially exhibit an austenite-stabilizing behavior but coarsening of the precipitates and chemical partitioning subsequently stabilizes martensite. Comparisons of strength, modulus, thermal hysteresis, and remnant strain will be made between experiments and molecular dynamics simulations.
4:40 PM
Microstructural Evolution in Oligocrystalline Fe-Mn-Al-Ni Shape Memory Alloys: Hande Ozcan1; Daniel Salas1; Ji Ma2; Ren Yang3; Yuriy Chumlyakov4; Ibrahim Karaman1; 1Texas A&M University; 2University of Virgina; 3Argonne National Laboratory; 4Tomsk State University
FeMnAlNi alloys have emerged as one of the most promising SMA candidates for large scale applications due to their cost-efficiency, excellent superelasticity and low temperature dependence of the critical stresses with a large superelasticity window. The superelastic performance of FeMnAlNi is dependent on the size of nano-precipitates, the crystallographic orientation of the grains and the ratio of relative grain size to the dimension of component. The fundamental understanding of the microstructure and the ability to increase the component dimension of the alloys for large scale applications is important in the development of FeMnAlNi alloys. In this study, the fundamental mechanisms behind the abnormal grain growth by thermal cycling was studied. A new crystal reorientation mechanism that results in abrupt crystallographic orientation changes in bulk single crystals is reported for the first time. The findings also open up new possibilities for the development of new large single crystals with tailorable orientations.