Late News Poster Session: Advanced Materials
Program Organizers: TMS Administration
Tuesday 5:30 PM
March 21, 2023
Room: Exhibit Hall G
Location: SDCC
J-99: Can the Effective Bond Energy Formalism (EBEF) Improve the CALPHAD Database for Co-based Superalloys?: Julio Cesar Pereira Dos Santos1; Chuan Liu2; Sean Griesemer2; Peisheng Wang3; Ursula Kattner4; Carelyn Campbell4; 1NIST / Northwestern University; 2Northwestern University; 3Central South University; 4NIST
As part of the CHiMaD/NIST project, a thermodynamic database for γ/γ’ Co-based superalloys composed of 10 elements is being developed. The original version of the database was developed using a traditional CALPHAD approach to describe complex topologically close-packed (TCP) phases such as sigma (σ), Laves (C14, C15 and C36), mu (μ) and chi (χ). However, the results showed the need to improve the description of these phases in some ternary systems constituting the entire database. Therefore, the effective bond energy formalism (EBEF) supported by new density functional theory (DFT) data is being implemented to properly describe these complex TCP phases. Promising preliminary results were obtained. A comparison between results using the classical CALPHAD approach and results using the EBEF is presented for some key ternary systems.
Enhanced High-temperature Elongation of Ni-based Superalloys by Reducing Co and Increasing Mo: Saurabh Tiwari1; Jae Hoon An1; Muhammad Ishtiaq1; Hyoju Bae1; Jae Bok Seol1; 1Gyeongsang National University
Ni-based superalloys are preferentially used for temperatures above ~600oC owing to their unique creep strength and stability against harsh environments which is standard criteria to ensure the efficient and safe application of used material. However, the addition of Re enhances the creep resistance but increases the overall cost also. The development of Re-free IN738LC, low-carbon alloys specifically for harsh environments reduced the overall cost. Still, the presence of other expensive elements as Co increases its cost. Here, we reduce the amount of Co (wt%) by ~50% and achieve the overall mechanical properties with increased elongation (~30%) at an elevated temperature of 750oC. This is achieved by reducing Co content and increasing the relatively cheaper Mo content. The annealed and deformed microstructure analyzed by SEM, EBSD, and ECCI reveals the change in the slip mechanism plays a significant role in enhancing the mechanical properties of Mo-modified IN738LC alloy.
J-100: In-situ Formation of Transition Metal-Aluminates as an Interfacial Modifier in YSZ based Cermets: Amanda Marotta1; David Driscoll1; Stephen Sofie1; 1Montana State University
Improving the mechanical properties of cermet composites is driven at the interface, where metallization and active brazing can be utilized. However, the incorporation of precipitates and solutes in the metal phase leads to degradation of the cermet’s functional properties. To overcome this, we propose introducing, in air, transition metal-aluminate phases to promote adhesion between metals and ceramics. To elucidate this interface, we explored the thermal and mechanical impact of YSZ cermets. Weibull analysis of Ni-YSZ exhibited a ~50% increase in modulus of rupture, when doped with nickel aluminate (NiAl2O4) and a clear resistance of metal migration on the ceramic at high temperatures with minimal degradation in electronic conduction. Comparably, for undoped Cu-YSZ, thermal cyclic variance gave evidence to interfacial degradation. When introducing copper aluminate (CuAl2O4) to Cu-3YSZ, thermal constraint of the cermet’s thermal expansion, suggests interfacial modifications between the ceramic and metal phases, preventing thermal degradation while preserving thermal conductivity.
J-101: Mechanical Behaviour of Forged Al5Co15Cr30Fe25Ni25 High Entropy Alloy: Pablo Perez1; Gerardo Garcés1; María Fernanda Vega2; Judit Medina1; Paloma Adeva1; 1CENIM-CSIC; 2INCAR-CSIC
Compressive behavior of forged Al5Co15Cr30Fe25Ni25 high entropy alloy was evaluated up to 700˚C. The material was processed by forging as-cast ingots at 1200˚C with a total reduction of 50 %. Compressive tests were performed on samples mechanized in the forging direction and perpendicularly to it. The results evidence the significant effect of sample orientation on the yield stress. The yield stress along the forging direction is higher than along the transverse direction. Such difference, of about 100 MPa at room temperature, tends to decrease as temperature increases. Disregarding the sample orientation, the yield stress is kept almost constant up to 500˚C, decreasing above this temperature due to the occurrence of dynamic recrystallization in the course of the compression test. Curves at 400 and 500˚C exhibit a jerky flow, associated with the pinning of dislocations by solute atoms, which probably accounts for the high strength of the HEA at these temperatures.
J-108: Mechanical Strengthening of a Soft-magnetic High-entropy Alloy via Widmanstätten Microstructure: Liuliu Han1; 1Max Planck Institute for Iron Research
For soft magnetic materials exposed to harsh environments, they need multi-dimensional property requirements, for instance, high strength and good ductlity to withstand mechanical loading conditions. Conventional magnets usually hard to access other corners of the property landscape in the same material. We recently proposed a generic solution to the alloy systems that are thermodynamically unfavourable for triggering coherent nanoprecipitates. We realized this by introducing incoherent Widmanstätten patterned precipitates into the ferromagnetic matrix of a non-equiatomic FeCoNiTa high-entropy alloy. Although micro-sized precipitates have been thought to be detrimental to soft magnetic properties due to the pinning effect on magnetic domain walls, such an effect is counteracted by reducing grain boundary pinning in our strategy. Further, at elevated temperatures, the high thermal stability of the Widmanstätten microstructure contributes to the better magnetic properties of the precipitate-containing alloy compared to that of the precipitate-free counterpart.