Alloy Phase Transformations at Elevated Temperatures: Session III
Sponsored by: TMS High Temperature Alloys Committee, TMS Phase Transformations Committee
Program Organizers: Dinc Erdeniz, University of Cincinnati; Benjamin Adam, Oregon State University; Jonah Klemm-Toole, Colorado School of Mines; Eric Lass, University of Tennessee-Knoxville; Ashley Paz y Puente, University of Cincinnati; Sophie Primig, University of New South Wales; Chantal Sudbrack, National Energy Technology Laboratory
Wednesday 8:00 AM
October 12, 2022
Room: 319
Location: David L. Lawrence Convention Center
Session Chair: Chantal Sudbrack, National Energy Technology Laboratory
8:00 AM Invited
Develop Precipitation-Strengthened Refractory High Entropy Alloys for Turbine Blades Applications above 1300 Degree Celsius: Michael Gao1; David Alman1; Chantal Sudbrack1; Paul Jablonski1; Vishnu Raghuraman2; Mike Widom2; Michael Kirka3; 1National Energy Technology Laboratory; 2Carnegie Mellon University; 3Oak Ridge National Laboratory
Improving the efficiency and decreasing CO2 emissions of aviation and land-based turbines will require increasing the temperature of the turbine operations. However, this increase is limited by the current state-of-the-art Ni-base superalloys. Thus, there is a need to develop next-generation refractory alloys for high-temperature service. The main challenge in developing these alloys is balancing room temperature ductility and fracture toughness with high temperature strength and creep resistance, while maintaining comparable oxidation resistance and densities to Ni-base superalloys. This project integrates multi-scale computational modeling with additive manufacturing (AM) and performance evaluation to rapidly design an AM processable, precipitation strengthened refractory high entropy alloy for use at 1300C and above. Presented will be high throughput CALPHAD and first-principles calculations used to rapidly design the alloy. Also presented will be the microstructure and mechanical properties in the as-cast and annealed conditions, and surrogate additive manufacturing (melt track) experiments of these alloys.
8:30 AM Invited
Precipitation Strengthening in BCC Al2.7CrMnTiV High-Entropy Alloys: Keith Knipling1; Patrick Callhan1; 1Naval Research Laboratory
Abstract: 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 thermodynamic predictions. 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 thermodynamic predictions. 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.
9:00 AM
Alternate Phase Transformation Paths in a Nb-50Ti Alloy in the Presence of Oxygen Interstitials: Ravit Silverstein1; Anirudh Natarajan2; Anton Van der Ven1; Carlos Levi1; 1University of California, Santa Barbara; 2University of California, Santa Barbara, California
Interstitials are well known to affect the phase stability and impact the performance of many structural alloys, including those based on BCC multi-principal elements (MPEs). As a part of a broader effort to understand the impact of interstitials in BCC refractory alloys, a study has been undertaken to address the role of relatively dilute concentrations of oxygen in a BCC equimolar Ti-Nb alloy. The study revealed that oxygen incorporation induces a miscibility gap within the BCC field, with potential for spinodal decomposition about the equimolar solution. The spinodal leads to modulation of Nb/Ti, with O redistributing preferentially to the Ti-rich regions. The latter then exhibits a primary transformation mechanism to HCP via a transient orthorhombic form, following the Burgers path. A secondary path through an intermediate omega phase is also observed. This presentation discusses the alternate paths and their current understanding.
9:20 AM
Additive Manufacturing Design of Metal Matrix Composites of Stainless Steel 316 and Inconel 718: Daozheng Li1; Wei Xiong1; 1University of Pittsburgh
Metal matrix composites (MMCs) have significantly improved mechanical and thermal properties in a wide range of engineering fields. However, the complicated manufacturing process and low cost-effect ratio are significant limitations in applications. Additive manufacturing (AM) simplifies the process of components using metal matrix composite with the layer-by-layer printing strategy for complex shapes. After the heat-treatment design, binder jet AM (BJAM) can produce MMCs with ideal mechanical and thermal properties that are higher than the bulk materials. MMC design using BJAM is presented in this work, followed by sintering and infiltration through ICME design. Stainless Steel 316L is selected to be the matrix material. The infiltration of the liquid Inconel 718 fulfills the gaps and the pores between the solid stainless steel (SS)316L powder particles with a significantly minimized porosity. After aging, γ” and γ’ precipitation in Inconel 718 reinforces the matrix SS316L even further with a significantly enhanced strength.
9:40 AM Invited
Precursor Metastable Phases and Their Influence on α Precipitation in the Metastable β-titanium Alloy, Ti-5Al-5Mo-5V-3Cr: Stoichko Antonov1; Zachary Kloenne2; Yufeng Zheng3; Rongpei Shi4; Hamish Fraser2; Baptiste Gault5; 1National Energy Technology Laboratory; 2The Ohio State University; 3University of Nevada, Reno; 4Harbin Institute of Technology; 5Max-Planck-Institut fur Eisenforschung
The microstructural evolution and mechanical performance of metastable β-titanium alloys can be significantly influenced by the thermo-mechanical treatment, during which formation of various nano-scaled phases occurs. The exploration of the structure and composition of these phases and their interplay with the ⍺ phase formation enables the understanding of the microstructural development. Subsequently, the knowledge can be used as a lever to tailor the microstructure and consequently the mechanical properties. In this study, we used in-situ and ex-situ conventional and aberration-corrected scanning/transmission electron microscopy and atom probe tomography to characterize the cascade of metastable phases forming in Ti-5Al-5Mo-5V-3Cr during heating to aging temperature, as well as their influence on the ⍺ distribution. The results show that the nucleation of ⍺ is strongly influenced by phases formed by diffusional-displacive transformations and are rich in Ti - ⍵, ⍺ʺ, and Oʺ - that serve as intragranular nucleation sites for ⍺.
10:10 AM Break
10:30 AM
Study of Thermal Decomposition of γ’-Fe4N Using Molecular Dynamics Simulation: Jianxin Zhu1; Jian-Ping Wang1; 1University of Minnesota
Recent research demonstrated experimentally through thermally quenching using γ’-Fe4N as precursor to synthesize α”-Fe16N2 in bulk format, a promising environment- friendly rare-earth-free permanent magnet with ultra-high saturation magnetization. In this research, we investigated γ’-Fe4N thin film thermal decomposition and potential localized fcc-bct phase transition using Molecular Dynamics (MD) simulation. As the nitrogen content is higher in γ’-Fe4N (5.9 wt.%) than that in α’-Fe8N or α"-Fe16N2 (3 wt.%), Localized Nitrogen "depletion” needs to occur during thermal decomposition to form possible bct Fe-N solid solution and/or α’ phase. Nitrogen bond forming and Nitrogen diffusion are the two pathways in reduction of Nitrogen in γ’-Fe4N. “Nitrogen-rich” and “Fe-rich” grain-boundary models are introduced to study these reduction mechanisms. We applied MEAM Fe-N force field, simulated Nitrogen bond form/breaking and local Nitrogen displacement analysis in the thermostat-controlled heating/quenching simulation. XRD and formation energy calculation are used to detect the potential phase transition.
10:50 AM
Thermal Stability and Time-temperature-transformation Diagrams of Co-rich Nanocomposite Ribbons: Yuankang Wang1; Paul Ohodnicki1; 1University of Pittsburgh
Co-rich amorphous and nanocrystalline (i.e. nanocomposite) ribbons exhibit excellent magnetic and mechanical properties with tunable characteristics through magnetic field and strain annealing methods, making it promising for applications such as inductors and current transformers. Of particular interest for space and other extreme environments are high temperature performance and stability. In this project, the thermal stability of Co-rich nanocomposite alloys at elevated temperature has been investigated. The phase transition behavior as a function of temperature and time was studied using differential scanning calorimetry (DSC). Transmission electron microscopy (TEM) and X-ray diffraction (XRD) were performed for the microstructure investigation. The results shows that the alloy exhibits two step crystallizations: CoFe-based primary crystallites at 430 oC and CoFe-rich borides at 645 oC. Detailed characterization of the microstructure stability combined with magnetic property evolution is studied indicating the alloy exhibits excellent thermal stability and is promising for magnet applications at elevated temperature.
11:10 AM
On the Shapes of Time-Temperature-Transformation Curves across Alloys and Reactions: Robert Hackenberg1; 1Los Alamos National Laboratory
Moving beyond the original use of TTT diagrams to capture proeutectoid ferrite, pearlite, and bainite, phase transformations as diverse as discontinuous precipitation and coarsening, continuous precipitation, order-disorder, spinodal decomposition, massive transformation, and isothermal martensite have been captured. Although the qualitative understanding of the C-curve shapes is well-established, comparison between theory and experiment of their quantitative shapes across multiple alloy systems and reactions is lacking. This work will examine the factors that determine relative locations of the various curves in alloys as a function of alloy content and diffusion mechanism. Consideration is given to alloys exhibiting multiple competitive reactions. The influence of measurement technique on the published curves will be one factor of interest, with a view towards their possible blind spots, biasing towards earlier vs later times, and convolution of simultaneous reactions. The emphasis will be on nonferrous, especially uranium alloys.