@article{kautz_yano_hartmann_gerard_taylor_scully_schreiber_2025, title={Strategies for Preparing and Analyzing Thin Passive Films With Atom Probe Tomography}, volume={31}, url={https://doi.org/10.1093/mam/ozaf023}, DOI={10.1093/mam/ozaf023}, abstractNote={Abstract Atom probe tomography (APT) provides a unique, three-dimensional map of elemental and isotopic distributions over a wide range of materials with near-atomic scale resolution and is particularly strong at analyzing buried interfaces within materials. However, it is much more difficult to apply atom probe to the analysis of nanoscale surface films, such as those formed during alloy passivation, where unique challenges persist for sample preparation and data collection. Here, we present sample preparation strategies involving the deposition of a <100 nm capping layer that enables reliable characterization of thin passive films ∼2–5 nm thick formed on binary and multiprincipal element alloys via APT. Several capping layer materials (Pt, Ti, and Ni/Cr bilayer) and deposition methods are contrasted. Our results indicate a sputtered Ni/Cr bilayer enables the characterization of the entire passive film and concentration profiles that can easily be interpreted to clearly distinguish base alloy/passive film/capping layer interfaces. Lastly, we highlight ongoing challenges and opportunities for this experimental approach.}, number={4}, journal={Microscopy and Microanalysis}, author={Kautz, Elizabeth J and Yano, Kayla H and Hartmann, Josephine C and Gerard, Angela Y and Taylor, Sandra D and Scully, John R and Schreiber, Daniel K}, year={2025}, month={Jul} }
 @article{hartmann_varga_schenck_mcrobie_tsai_shutthanandan_devaraj_senor_gwalani_kautz_2025, title={Structure evolution and tin redistribution during oxidation of Zircaloy-4 at 500°C}, volume={614}, url={https://doi.org/10.1016/j.jnucmat.2025.155895}, DOI={10.1016/j.jnucmat.2025.155895}, abstractNote={Zirconium (Zr) alloys are widely used as fuel cladding in nuclear power reactors due to their thermal stability, mechanical durability, corrosion resistance, and low neutron absorption cross-section. However, their performance is challenged by oxidation in reactor environments, making the study of Zr alloy corrosion behavior crucial for ensuring the safety, longevity, and economic viability of nuclear power systems. While the oxidation behavior of Zr-based cladding materials has been extensively studied since the 1950s, a mechanistic understanding into the relationship between structure evolution, solute element redistribution, and properties remains elusive. Valuable insights may be obtained through advanced experimental methods, such as in-situ and high resolution microscopy techniques. In this study, the oxidation behavior of Zircaloy-4 at 500 °C in O 2 is characterized using a multimodal advanced characterization approach. Using in-situ X-ray diffraction, the phase evolution from metastable to stable oxides is tracked in real time. Complementary high-resolution techniques, including electron microscopy and atom probe tomography, reveal nanoscale insights into the microstructural changes and solute redistribution across the oxide/metal interface. Nanohardness mapping across the oxide/metal interface highlights localized mechanical property variations that may be linked to changes in microstructure and crystal structure within the oxide layer. These findings offer valuable insights into the microstructure and property evolution of Zircaloy-4 during oxidation, contributing to a better understanding of microstructural changes in Zr-based alloys under oxidative environments.}, journal={Journal of Nuclear Materials}, author={Hartmann, Josephine and Varga, Tamas and Schenck, Caleb and McRobie, Chris and Tsai, Fu-Yun and Shutthanandan, Vaithiyalingam and Devaraj, Arun and Senor, David and Gwalani, Bharat and Kautz, Elizabeth}, year={2025}, month={May} }
 @article{rizvi_uddin_mcrobie_hartmann_malakar_yano_barton_tsai_laggner_gwalani_et al._2025, title={Ultrafine-Grained Al/Al2Cu Composite Formation via Friction Stir Processing of Cold-Sprayed Coatings}, volume={9}, url={https://doi.org/10.1007/s11837-025-07741-0}, DOI={10.1007/s11837-025-07741-0}, abstractNote={Abstract We demonstrate a shear-deformation-driven, solid-state phase transformation pathway for the formation of an ultrafine-grained Al/Al $$_2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mn>2</mml:mn> <mml:mrow/> </mml:mmultiscripts> </mml:math> Cu composite via friction stir processing of a Cu cold-sprayed coating on an AA6061 aluminum substrate. This approach leverages the severe plastic deformation and high strain-rate environment inherent to friction stir processing to drive localized interdiffusion and solid-state reactions between the Cu coating and the Al alloy substrate. The processed surface exhibits a significant increase in hardness ( $$\approx $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mo>≈</mml:mo> </mml:math> 250 HV), compared to both the AA6061 substrate ( $$\approx $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mo>≈</mml:mo> </mml:math> 100 HV) and the as-deposited Cu coating ( $$\approx $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mo>≈</mml:mo> </mml:math> 132 HV); these measured hardness values represent an increase of 1.8-times and 2.4-times relative to the Cu CS coating and AA6061 substrate, respectively. This hardness enhancement is attributed to the uniform distribution of fine-grained Al $$_2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mn>2</mml:mn> <mml:mrow/> </mml:mmultiscripts> </mml:math> Cu reinforcement within an Al(Cu) matrix, as confirmed by transmission electron microscopy and atom probe tomography. Unlike conventional precipitation hardening, here, discrete Al $$_2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mn>2</mml:mn> <mml:mrow/> </mml:mmultiscripts> </mml:math> Cu grains are directly formed and dispersed among Al grains, resulting in a hetero-grained microstructure that transitions into a single-phase matrix below the processed zone. Our results demonstrate the potential of integrating solid-state deposition with high-speed mechanical mixing to generate unique, non-equilibrium microstructures that bypass equilibrium melting constraints and exceed the performance of conventional thermomechanical processing routes.}, journal={JOM}, author={Rizvi, Syed Muhammad Mujtaba and Uddin, Md Jasim and McRobie, Chris and Hartmann, Josephine and Malakar, Aniruddha and Yano, Kayla and Barton, Dallin and Tsai, Fu-Yun and Laggner, Florian and Gwalani, Bharat and et al.}, year={2025}, month={Sep} }