Ohio State Materials and Manufacturing Conference Program

Over a century ago, material innovations like novel aluminum casting and judicious selection of natural materials propelled aviation pioneers into the skies.  Unquestionably, the future of aerospace will be as unrecognizable from today as the early Wright Flyer and Goddard’s rockets are from today’s F-47 and Starship.  However, the crucial role of materials and manufacturing will remain unchanged – they will be the essential ingredient that enables future machines to push the performance envelope beyond todays.  Success hinges on a fundamental shift in approach: from asking "what is the next material" to "how do we revolutionize the process of research."  Embracing the tools of the digital age will accelerate discovery, slash development timelines and costs, and create a more nimble and responsive manufacturing ecosystem, from the supply chain to maintenance depots.

Spacecraft materials in low Earth orbit (LEO) are challenged by atomic oxygen, charged-particle radiation, micrometeoroid and orbital debris impacts, thermal cycling, and UV radiation, all of which contribute to material degradation. The OSU-led SPACE-Mat Center of Excellence addresses these challenges by developing predictive physical and data-driven models that reliably forecast material lifetimes under realistic LEO conditions with quantified uncertainties. SPACE-Mat is developing computational lifetime prediction capabilities for widegap semiconductors and structural polymers through physics-based and data driven models, based on a multidisciplinary approach integrating previous data from NASA’s Materials International Space Station Experiments (MISSE), new data from in-lab experiments in facilities simulating the LEO environment, detailed simulation down to the atomic level, and rigorous multiscale characterization. In this talk, we will first describe the general framework developed to understand degradation of materials in the LEO environment, predict their lifetime within space systems, and design strategies for identifying longer-lived materials. Following this, we present detailed findings on the impacts of the space environment on wide-gap semiconductors – specifically GaN and Ga₂O₃ – and on polyimide films used in thermal blankets, which protect electronics and components from the extreme temperature fluctuations and radiation in space.

As countries and private companies around the world have engaged in a new space race, not only to explore but also to use Space and colonize other cosmic objects like the Moon, Mars, and even asteroids, manufacturing in space is no longer a distant and expensive dream but a pressing need. Therefore, materials joining in space has become a critical enabling technology for the rapidly growing in-space servicing, assembly, and manufacturing (ISAM) sector. Today, no metallurgical joining processes have been proven fit-for-service for execution in space. There is limited fundamental understanding of the effects of the space environment (gravity, atmosphere, and temperature) on the joining processes, the metallurgy, and performance of the resultant joints. This current inability to effectively join materials in space significantly impairs the advancement of space exploration and economy. Our team, which also involves several members from the NASA MSFC, LRC, and GRC, investigates the impact of space conditions on the Laser Beam Welding (LBW) of metallic alloys. For this purpose, a 1 kW, 1070nm Yb-fiber pulsed laser was fitted into a vacuum chamber with cryocooling for microgravity experiments. To mimic space, our experimental setup rides aboard a parabolic flight where high-vacuum, extreme temperatures, and variable gravity (from µg to 1.8g) experiments address the impact on weld geometry, microstructure, and defect formation on Al-Fe- and Ti-based alloys. Our current results on LBW on stainless steels show findings that differ from the literature on microgravity. CT scans of the welds demonstrated a decrease in porosity for microgravity welds and a lower pore aspect ratio. Welds on Earth’s gravity and in microgravity had similar microstructural features. This research represents a significant step toward qualifying LBW for ISAM applications and supports the broader goal of enabling autonomous, on-demand fabrication and repair in orbit and beyond. Finally, the insights gained from this work are contributing towards our efforts to develop robust and predictive Integrated Computational Materials Engineering (ICME) frameworks and help establish design and process qualification standards for welding in space.

A.J. Ramirez, B. Panton, K.C. Riffel, A. Nassiri, E. Choi, A. Brimmer, W. McAuley

Welding Engineering Program, Dept. of Mater. Sci. and Eng. - The Ohio State University

For decades, it has been known that oxide dispersion strengthening (ODS) is one of the most effective means of producing creep-resistant alloys.  However, the widespread deployment of ODS has been limited by the complex, conventional processing route to create these alloys involving mechanical alloying and subsequent thermomechanical processing.  A new additive ODS process using laser powder bed fusion has recently been developed by collaborators at NASA Glenn Research Center and enables the synthesis of ODS alloys in a single step [1].  This route has been utilized to design an ODS solid solution alloy (GRX-810) which has exceptional high temperature properties when compared with other solid solution Ni-base superalloys [2].  Detailed electron microscopy analysis has been performed to characterize the structure and composition of the oxide dispersoids, and other minor grain boundary phases.  These microstructure insights are being used to understand the significantly improved creep resistance of GRX-810 in comparison to a model NiCoCr ODS alloy.  The present status of this work, understanding of strengthening mechanisms, and prospects for developing a wider range of ODS strengthened alloys will be discussed.

For decades, GaN promised to be the material of future for power switching applications. Through recent advancements in process technologies, GaN power switching devices are now delivering on the promise by enabling new applications as well as replacing Si in many existing applications. However, there are significant challenges ahead to push the performance and reliability of GaN devices from “better than others” to converging towards its full potential. In this presentation, we present process technologies facilitating the improvements and requirements for future roadmap of GaN power switching. 

Ultra-wide bandgap AlGaN lateral transistors are promising for high frequency power amplifier applications as their higher breakdown field and comparable saturation velocity enables improved Johnson Figure of Merit (JFOM) over GaN lateral transistors. In this work, we discuss the demonstration of a structure that includes two important design features. Firstly, we use polarization-graded AlGaN layers which have been shown to have benefits for linearity, breakdown, and carrier transport. Secondly, we employ ultra-thin psuedomorphic AlGaN buffer/channel layers that enable very low thermal resistance to overcome the low thermal conductivity of AlGaN and at the same time, ensure excellent structural quality. The polarization-graded field effect transistors (PolFETs) demonstrated here show I_max over 800mA/mm and f_T/f_max of 26/28 GHz. These results are a state-of-art combination of current density and f_T-L_G product for ultra-wide bandgap AlGaN transistors, show the promise of AlGaN transistors for future mm-wave and RF applications.

In this talk, we will first present the device design of a vertical GaN-on-GaN PN power diode using a double field plate structure and guard-rings for electrical field management to achieve high breakdown voltages. The fabricated diode with a ~74 μm thick drift layer and Nd-Na concentration of 1´10¹⁵ cm^-3 demonstrated a breakdown voltage of 11.45 kV on a bulk GaN substrate. The device has an on-resistance of 8 mΩ·cm² and a Baliga figure of merit (BFOM) of 13 GW/cm². To our knowledge, the measured breakdown voltage is the highest among any reported vertical GaN power devices. Using the experimental data of fabricated devices, we extracted the breakdown field and mobility in GaN as a function of doping density ranging from high 10¹⁴ to low 10¹⁶ cm^-3. The results suggest that GaN has clear advantages over SiC especially on mid- to high voltage rating devices.

Yibo Xu, Vijay Gopal Thirupakuzi Vangipuram, Hongping Zhao, Senior Member, IEEE, and Wu Lu, Senior Member, IEEE 

Development of high-temperature compatible electronic devices is desired for hypersonic vehicles, space exploration, electric vehicles, gas turbines, gas/oil drilling, geothermal surveying, and energy-dense systems. Electronic devices made with wide bandgap and ultra-wide bandgap materials are suitable for these high temperature applications. In this talk, we will present high temperature device data obtained from β-Ga2O3 field-effect transistors (FETs) and AlGaN/GaN high-electron mobility transistors (HEMTs) at temperatures up to 500 oC. We will discuss device details, analyze the electrical data by considering insights obtained from materials characterization, and explain the variation in device parameters (such as transconductance, threshold voltage, contact resistance, gate leakage) with temperature and time. 

Ahmad Islam (AFRL-Sensors Directorate), Biddut Sarker (KBR, Inc.), Nicholas Sepelak (KBR, Inc.), Weisong Wang (Wright State University), Andrew Green (AFRL-Sensors Directorate), Kelson Chabak (AFRL-Sensors Directorate)

The influence of electric fields on defect formation and migration in β-phase gallium oxide (β-Ga2O3) is critical for understanding device degradation and failure mechanisms. To investigate this behavior, Si-doped β-Ga2O3 epilayers grown via metal-organic chemical vapor deposition were irradiated with 1.8 MeV protons, and the resulting defects were analyzed using defect spectroscopy techniques. The study revealed higher carrier removal rates (CRR) compared to our previous findings under similar conditions, aligning with the broad range of values reported in the literature. This work elucidates the mechanisms driving CRR variability, particularly concerning defect generation. In contrast, partial carrier recovery occurred at room temperature, attributed to reduced defect migration barriers by applied electric fields. This effect demonstrated a linear dependence on electric field strength. Complete carrier recovery was achieved through isochronal annealing at 200-400°C without bias, indicating a thermally and field-activated recovery mechanism. Post-annealing analysis revealed net ionized doping concentrations corresponding to a single thermal activation energy of 1.1 eV. Additionally, defect spectroscopy identified activation energies for radiation-induced defects, linking them to primary compensating centers responsible for CRR removal and recovery. The underlying mechanism causing CRR non-uniformity is identified and will be presented at the conference.

Orthorhombic-structured II-IV nitrides provide a promising opportunity to expand the material platform while maintaining compatibility with the wurtzite crystal structure of the traditional III-nitride material system. II-IV-nitrides provide opportunities to develop materials with new fundamental properties that can potentially address challenges facing current device technologies based on pure III-nitrides. Among them, MgSiN₂ stands out due to its close compatibility with GaN and AlN and its theoretically predicted ultrawide indirect bandgap of 5.84 eV. MgSiN₂ is also theoretically predicted to possess a direct bandgap of 6.28 eV. In this work, metal-organic chemical vapor deposition (MOCVD) growth of MgSiN₂ thin films on GaN-on-sapphire and c-plane sapphire substrates was investigated.  Comprehensive material characterization was performed to correlate the MgSiN₂ crystalline quality with the MOCVD growth conditions. Effects on stoichiometry, crystallinity, and surface morphology were analyzed via SEM-EDS, XRD, high-resolution STEM, and AFM. Transmittance measurements were used to determine the optical band gap, yielding direct bandgap values between 6.13 eV and 6.27 eV for samples grown under varying conditions. Indirect bandgap values were also extracted, ranging from 5.77 eV to 5.81 eV. These results confirm the realization of ultrawide bandgap, III-nitride compatible, single crystalline II-IV-nitride thin films.

Neutral atoms have emerged in recent years as a leading qubit candidate for quantum computing. Atom interferometers, meanwhile, provide precise measurements of very weak gravitational forces. Both of these applications use optical fields to write-in / read-out information, as well as to trap and manipulate the atoms. Optical resonators have been used to enhance such atom-photon interactions, constituting the field of cavity quantum electrodynamics (QED).

In this talk, I will discuss two experiments being designed and built in our new lab at Montana State University. The first will develop and utilize novel high numerical aperture optical resonators enabling strong single-atom/single-photon coupling even at low to moderate finesse. I will describe use cases of these resonators with neutral atom qubits, such as Purcell-enhanced cavity tweezer arrays for fast readout, entanglement distribution and scalable trapping. The second experiment uses a more traditional cavity geometry to realize a compact, high-sensitivity mobile atomic gravimeter / gradiometer. Such an apparatus can be small enough to serve as a drone payload, with sufficient sensitivity to conduct relevant field surveys of gravitational signatures in geophysics, underground resource monitoring, and non-invasive archaeology.

Arrays of optically trapped neutral atoms have emerged as a versatile and powerful architecture for quantum information processing, featuring high-fidelity Rydberg gates and programmable any-to-any qubit connectivity with hundreds of qubits. Due in part to their long coherence times and excellent measurement discrimination fidelities, neutral atom arrays are ideal platforms for exploring measurement-based protocols and real-time in-sequence quantum feedback control, including quantum error correction. In this talk, I will discuss how introducing a second atomic species in the array enables crosstalk-free mid-circuit measurements that can be used to measure and control a primary species. We use measurements on the second species (auxiliary qubits) to correct correlated phase errors on the first species (data qubits) using in-sequence feedback. Furthermore, I will discuss the richness of Rydberg interaction regimes that can be accessed in the system and how we achieve enhanced interspecies Rydberg interactions using a Forster resonance. In this regime, we demonstrate interspecies Rydberg blockade and use this blockade to generate Bell states between hyperfine qubits of different atomic elements (Rb and Cs). Lastly, I will discuss how we combine this interspecies entanglement with native mid-circuit readout to achieve quantum non-demolition measurements of data qubits utilizing a set of auxiliary qubits. These new measurement capabilities, combined with the richness of Rydberg interactions, open up compelling directions in quantum state control, quantum feedback, and many-body physics. 

When a many-body quantum system undergoes unitary (quantum) evolution in time that is punctuated by sporadic measurements, the behavior of its entanglement can fall into one of two broad classes. These are called the “entangling” and “disentangling” dynamical phases. Separating the two phases is a “phase transition”, which corresponds to an abrupt change in the nature of entanglement in the system as a function of the measurement rate or measurement strength. In this talk I describe the idea behind the measurement phase transition and I present recent progress in finding exact solutions for its properties and in realizing the transition experimentally.

Quantum sensors hold promise for improved sensing of time, electromagnetic fields, and forces; however, the inherent probabilistic nature of quantum mechanics introduces uncertainty that can limit sensor precision. We can hope to overcome this uncertainty by engineering entanglement to create correlated behavior in atomic systems. Unfortunately, in practice, introducing and controlling these correlations is limited by the local nature of interactions on many promising sensing platforms, including optical tweezer clocks and solid-state magnetometers. In this talk, I will discuss how we can use temporal control over local Rydberg interactions to extend interaction coherence times in an array of atomic ensembles, generating metrologically useful entanglement across several spatially separated ensembles in parallel. I will then discuss a general framework for understanding and improving correlation growth using locally interacting Hamiltonians. This work demonstrates the power of dynamical control to enhance and expand our understanding of entanglement in atomic systems. I will conclude by discussing future prospects in quantum sensing, simulation, and optimization on a new experiment utilizing a Rydberg atom array in an optical cavity.

In this talk, I will present measurement results from the first Quantum Key Distribution (QKD) link between two buildings on the Ohio State University Campus. The QKD link is implemented utilizing in-ground optical fiber that interconnects flying qubits from a transmitter in one building to a receiver in a second building. Measurements of secure key rate and quantum bit error rate will be discussed in addition to the vision of expanding the link to a test bed for system, component, and materials researchers. 

Van der Waals (vdW) heterostructures offer an unprecedented platform for engineering the physical properties of two-dimensional (2D) materials through control of twist angle, strain, and environmental interactions. The advent of state-of-the-art angle-resolved photoemission spectroscopy with nanoscale spatial resolution (nanoARPES), combined with its ability to probe fully functional devices, has opened new avenues for directly visualizing exotic electronic phenomena in these systems. In this talk, I will present our work leveraging cutting-edge in-operando nanoARPES to directly map the electronic properties of vdW heterostructures and their functional devices. I will highlight experiments that demonstrate on-demand tuning of the electronic structure by varying the substrate, twist angle, alkali metal doping, and applying an electric field. First, I will discuss the formation of quasiparticle-like trions and polarons arising from strong many-body interactions in transition metal dichalcogenide (TMD)-based heterostructures. Next, I will present our recent findings on the electronic structure of bilayer graphene on two distinct insulating substrates—hBN and RuCl₃—revealing intriguing new features. Time permitting, I will show our work on the thickness dependent electronic band structure of topological semimetals and their devices.

We investigated coupling a metal to the Mott insulator in an interface environment to study the effect this had on the production of these doublon-hole pairs and the resultant high harmonics at the interface. We find that interfacial coupling of a metal to the Mott insulator enhances high harmonic production inside the insulator and suggested an increase in the doublon-hole correlation length as the physical mechanism behind this lowered threshold for dielectric break-down.

A.S. Landsman, A. AlShafey (OSU), M. Randeria (OSU), Y.M. Lu (OSU), S.S. Gong (Great Bay University), X.Y. Jia (Beihang University), G. McCaul (Tulane), D. Bondar (Tulane), T. Oka (U. Tokyo)

Low-dimensional systems and their atomically precise heterostructures are a modular material platform to study emergent spin and magnetism related phenomena. I will present our work(s) on exploring topological semimetals and layered magnets based low-dimensional heterostructures to realize novel spin-galvanic effects for electric field control of the magnetic order, demonstrate a new type of unidirectional magnetoresistance, and realize an unconventional form of anomalous Hall effect. First, I will discuss our experiments to employ an out-of-plane oriented spin-current generated in a topological semimetal with low-symmetry crystal structure to deterministically switch and read the magnetic state(s) of perpendicularly polarized magnets. Secondly, I will discuss the experimental realization of unconventional form of anomalous Hall effect in a low-dimensional heterostructures, which is proportional to not only out-of-plane magnetization but also to in-plane magnetization component, potentially expanding the parameter space for designing dissipationless edge transport in low-dimensional systems. Furthermore, spin-defects can be engineered in low-dimensional systems – an appealing prospect for quantum sensing technologies. Time permitting, I will present our work aimed at utilizing designer spin defects embedded in a two-dimensional system to probe broadband spin dynamics.

The thermoelectric effect is a phenomenon in which a difference in temperature across a solid material induces a difference in voltage. The effect is potentially of great practical importance, since it allows one to convert waste heat into useful electric power. Here I discuss how "topological" semimetals, which represent a new class of materials outside the traditional dichotomy of all solid materials as either metals or insulators, can display unprecedented thermoelectric properties. I give an overview of the theory and then show experimental data for two topological semimetals: one (Bi_{1-x}Sb_{x}) that shows a record thermoelectric response in the longitudinal direction and another (YbMnBi_2) that shows a record thermoelectric response in the perpendicular direction.

Brian Skinner and Joseph Heremans, Ohio State University

The realization and discovery of quantum spin liquid (QSL) candidate materials are crucial for exploring exotic quantum phenomena and applications associated with QSLs. Most existing metal–organic two-dimensional (2D) quantum spin liquid candidates have structures with spins arranged on the triangular or kagome lattices, whereas honeycomb-structured metal–organic compounds with QSL characteristics are rare. In this talk, we report the use of 2,5-dihydroxy-1,4-benzoquinone (X2dhbq, X = Cl, Br, H) as the linkers to construct cobalt(II) honeycomb lattices (NEt4)2[Co2(X2dhbq)3] as promising Kitaev-type QSL candidate materials. Our results indicate that these 2D cobalt benzoquinone frameworks are promising Kitaev QSL candidates with chemical tunability through ligands that can vary the magnetic coupling and frustration.

Prof. Yiying Wu, OSU, Chemistry and Biochemistry

Van der Waals (vdW) heterostructures offer an unprecedented platform for engineering the physical properties of two-dimensional (2D) materials through control of twist angle, strain, and environmental interactions. The advent of state-of-the-art angle-resolved photoemission spectroscopy with nanoscale spatial resolution (nanoARPES), combined with its ability to probe fully functional devices, has opened new avenues for directly visualizing exotic electronic phenomena in these systems. In this talk, I will present our work leveraging cutting-edge in-operando nanoARPES to directly map the electronic properties of vdW heterostructures and their functional devices. I will highlight experiments that demonstrate on-demand tuning of the electronic structure by varying the substrate, twist angle, alkali metal doping, and applying an electric field. First, I will discuss the formation of quasiparticle-like trions and polarons arising from strong many-body interactions in transition metal dichalcogenide (TMD)-based heterostructures. Next, I will present our recent findings on the electronic structure of bilayer graphene on two distinct insulating substrates—hBN and RuCl₃—revealing intriguing new features. Time permitting, I will show our work on the thickness dependent electronic band structure of topological semimetals and their devices.

The fabrication of lithium-ion electrodes typically involves four key steps: mixing, coating, drying, and calendering. Despite extensive research in recent years, the influence of each step and their associated process parameters on the final electrode microstructure and performance has not been thoroughly investigated. In this study, a novel multi-scale, multi-physics computational framework is developed to predict process-to-property relationships in lithium-ion cathode manufacturing. First, using discrete element method (DEM), slurry containing active materials, a carbon-binder domain, and solvent was created. Second, a macro scale computational fluid dynamics (CFD) model was constructed to mimic the coater and drying step. Third, the CFD model was coupled with thermo-mechanical finite element model and DEM to simulate the calendering step and predict how variations in manufacturing process parameters affect the microstructure, performance, and aging characteristics of lithium-ion cells. To validate the numerical simulation results, experimental test was conducted for NMC 111 cathode electrode. Materials characterization including scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and micro-CT were performed at various cross-sections to analyze the formation of microstructure. The numerical simulation results also predict the onset of crack formation and delamination phenomena which are considered the main failure mechanisms in cathode electrode fabrication process.

The search for new battery materials is often slow and expensive, but artificial intelligence (AI) and machine learning (ML) offer a compelling alternative: discovering breakthrough materials in a fraction of the time. In this talk, I will discuss how small-data ML – when effectively paired with well-selected proxy properties that can be estimated from first-principles simulations or high-throughput experiments – can drive the rapid discovery of high-performance, low-cost battery materials. Our proposed framework, SPARKLE, integrates computational chemistry with novel ML algorithms to efficiently explore vast chemical spaces. We demonstrate its effectiveness in the discovery of organic (sustainable) cathode materials for aqueous zinc-ion batteries (AZIBs), identifying thousands of promising candidates from a design space of approximately one million molecules, despite labeled property data being available for less than 1% of the space. Experimental validation of a subset of these materials in real-world AZIB devices showed a threefold improvement in success rate over expert-driven selection, with several candidates outperforming state-of-the-art benchmarks while remaining cost-effective and synthesizable. I will highlight the key factors that enable this accelerated discovery process and discuss challenges that may arise when deploying similar approaches in new applications, along with potential strategies to overcome them.

Advancing novel materials requires precise analysis of atomic structure and defects to understand their impact on electronic, functional, thermal, and mechanical properties. This presentation will provide a broad overview of the pioneering research led by my group, utilizing and advancing CEMAS capabilities including high resolution quantitative STEM, 4D-STEM, EELS, and EBSD to drive scientific innovation. Through strategic collaborations with multiple research centers at OSU and external institutions, we have led transformative discoveries across diverse materials systems. Key topics will include ultrawide bandgap semiconductors and atomic scale defect engineering, novel magnetic interfaces that enable emergent properties, next generation energy storage materials, disordered materials for structural and functional applications, remote epitaxy, and the development of cutting edge electron microscopy techniques for probing thermal properties. By showcasing these advancements, this talk will highlight CEMAS’s leadership in materials research and its role in driving creative solutions to critical scientific challenges.

Electron ptychography is emerging as a transformative imaging technique for quantum materials. By scanning a coherent electron probe and iteratively reconstructing the specimen’s phase from diffraction patterns, multi-slice electron ptychography enables retrieval of the three-dimensional electrostatic potential at atomic resolution. This method achieves deep sub-ångström lateral resolution (~0.4 Å), fundamentally limited only by atomic thermal vibrations, and depth resolution of a few nanometers. Crucially, its quantitative phase sensitivity reveals subtle atomic-scale features invisible to conventional microscopy, including precise positions of light elements such as oxygen and lithium, picometer-scale atomic displacements, and hidden polar distortions at complex interfaces. In this talk, I will highlight how recent applications of multi-slice electron ptychography are deepening our understanding of quantum materials. By providing unprecedented experimental access to these structural details in three dimensions, electron ptychography facilitates more direct and quantitative connections between theoretical predictions and experimental observations. These insights are crucial for exploring and harnessing emergent quantum phenomena.

CEMAS is a unique, world-class electron microscopy facility that allows all electron microscopy instruments to perform better than manufacture specifications. The facility has been optimized to minimize electrical, thermal, acoustic, and pressure variations that lead to instrument instability and reduced instrument performance. CEMAS has designed a custom, remote operational control system to enables instrument operation and teaching at various locations nationwide and within Wright-Patterson Air Force Base’s materials characterization facility, as well as enabling over-the-shoulder collaborations with academia, and industrial partners worldwide. CEMAS provides one of the most impactful locations for placement of analytical electron microcopy instruments bringing together multidisciplinary expertise to drive synergy and amplify characterization capabilities, challenging what is possible with electron microscopy. CEMAS staff include 8 Ph.D. staff and 11 staff in total, providing a wealth of microscopy knowledge and experience across life science and physical sciences to apply current characterization techniques and work to develop new methods and techniques in collaboration with world experts across academia, industry, and governmental agencies. CEMAS has an agile business model to encourage testing services and is the ideal partner to work with to develop new solutions for informing major materials challenges as they arise.

Metastable beta titanium alloys have attracted significant attentions in the aerospace industry due to their high strength, low density, and excellent toughness. Various nanostructures can form in metastable beta titanium alloys, affecting their microstructure evolution under different service environment. Understanding the nature of these nanostructures from atomic scale using advanced transmission electron microscopy is essential to design the next generation of titanium alloys with tailored properties. In this presentation, we will introduce our recent studies of various nanostructures in metastable titanium alloys using aberration-corrected scanning transmission electron microscopy (ACSTEM). Our first study identifies a novel ordered orthorhombic O” phase in a Ti-5Al-5Mo-5V-3Cr alloy. By combining ACSTEM and 3D atom probe tomography, we demonstrate that the nanoscale Al-rich O” phase can promote finescale alpha precipitation in titanium alloys. In the second case, we characterize the nanostructures in a coldrolled Ti-24Nb-4Zr-8Sn alloy. Using diffraction contrast transmission electron microscopy and ACSTEM, we reveal the formation of nanoscale omega phase and alpha” phase at the deformation twin boundaries and identify the role of these nanostructures during deformation. Our studies provide new insights into the nanostructure-mediated microstructure evolution in metastable beta titanium alloys, contributing to the design of next-generation titanium alloys through microstructure engineering.

Superalloys exhibit exceptional high-temperature capabilities owing to their characteristic two-phase γ/γ’ microstructure. Here, we present an optimized pre-deformation strategy to further refine this microstructure by introducing an extremely high density of two-dimensional defects (about 25 defects per precipitate) into the alloy prior to creep deformation. High-resolution structural and chemical investigations using advanced electron microscopy reveal that these planar defects have locally transformed into ordered hexagonal phases. The introduction of such high defect density significantly enhances both yield and creep strengths up to 750 °C compared to the undeformed reference state. Additionally, we propose a complementary approach utilizing additive manufacturing as an alternative to plastic deformation for introducing high densities of locally transformed defect phases.