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1. Influence of Controlled Cooling Rates During Thermal Processing of Ti 6% Al 4% V Alloys Using In-Situ Scanning Electron Microscopy

   https://doi.org/10.1557/adv.2020.190  

   Kane, Genevieve A ; Frey, M. David ; Hull, Robert ( January 2020 , MRS Advances)

   ABSTRACT We describe experimental approaches to real time examination of the microstructural evolution of Ti 6%Al 4%V upon cooling from above the beta transus (~995 °C) while imaging in the scanning electron microscope. Ti 6%Al 4%V is a two phase, α+β titanium alloy with high strength and corrosion resistance. The β →α transformation on cooling can give rise to different microstructures and properties through various thermal treatments. Fully lamellar microstructures, bi-modal microstructures, and equiaxed microstructures can each be obtained by accessing different cooling rates upon the final treatment above the beta temperature, each resulting in uniquely enhanced material properties. Utilizing the capabilities of a heating/ tensile stage developed by Kammrath & Weiss Inc., are able to apply real-time imaging techniques in the scanning electron microscope to monitor the development of the microstructure. Annealing temperatures up to 1100 °C are attainable, with cooling rates ranging from 0.1 ° C per second to 3.3 °C per second. This has allowed us to directly observe the formation of lamellae at different annealing temperature/ cooling rate combinations to determine the lamellar microstructure width, separation, and colony size. 

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2. Lattice Parameter Evolution during the β-to-α and β-to-ω Transformations of Iron- and Aluminum-Modified Ti-11Cr(at.%)

   https://doi.org/10.3390/cryst14020145  

   Ballor, JoAnn ; Poplawsky, Jonathan D. ; Devaraj, Arun ; Misture, Scott ; Boehlert, Carl J. ( February 2024 , Crystals)

   β-titanium (β-Ti) alloys are useful in diverse industries because their mechanical properties can be tuned by transforming the metastable β phase into other metastable and stable phases. Relationships between lattice parameter and β-Ti alloy concentrations have been explored, but the lattice parameter evolution during β-phase transformations is not well understood. In this work, the β-Ti alloys, Ti-11Cr, Ti-11Cr-0.85Fe, Ti-11Cr-5.3Al, and Ti-11Cr-0.85Fe-5.3Al (all in at.%), underwent a 400 °C aging treatment for up to 12 h to induce the β-to-ω and β-to-α phase transformations. Phase identification and lattice parameters were measured in situ using high-temperature X-ray diffraction. Phase compositions were measured ex situ using atom probe tomography. During the phase transformations, Cr and Fe diffused from the ω and α phases into the β matrix, and the β-phase lattice parameter exhibited a corresponding decrease. The decrease in β-phase lattice parameter affected the α- and ω-phase lattice parameters. The α phase in the Fe-free alloys exhibited α-phase c/a ratios close to those of pure Ti. A larger β-phase composition change in Ti-11Cr resulted in larger ω-phase lattice parameter changes than in Ti-11Cr-0.85Fe. This work illuminates the complex relationship between diffusion, composition, and structure for these diffusive/displacive transformations.

    

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3. Pitting Corrosion in 316L Stainless Steel Fabricated by Laser Powder Bed Fusion Additive Manufacturing: A Review and Perspective

   https://doi.org/10.1007/s11837-022-05206-2  

   Voisin, T. ; Shi, R. ; Zhu, Y. ; Qi, Z. ; Wu, M. ; Sen-Britain, S. ; Zhang, Y. ; Qiu, S. R. ; Wang, Y. M. ; Thomas, S. ; et al ( March 2022 , JOM)

   316L stainless steel (316L SS) is a flagship material for structural applications in corrosive environments, having been extensively studied for decades for its favorable balance between mechanical and corrosion properties. More recently, 316L SS has also proven to have excellent printability when parts are produced with additive manufacturing techniques, notably laser powder bed fusion (LPBF). Because of the harsh thermo-mechanical cycles experienced during rapid solidification and cooling, LPBF processing tends to generate unique microstructures. Strong heterogeneities can be found inside grains, including trapped elements, nano-inclusions, and a high density of dislocations that form the so-called cellular structure. Interestingly, LPBF 316L SS not only exhibits better mechanical properties than its conventionally processed counterpart, but it also usually offers much higher resistance to pitting in chloride solutions. Unfortunately, the complexity of the LPBF microstructures, in addition to process-induced defects, such as porosity and surface roughness, have slowed progress toward linking specific microstructural features to corrosion susceptibility and complicated the development of calibrated simulations of pitting phenomena. The first part of this article is dedicated to an in-depth review of the microstructures found in LPBF 316L SS and their potential effects on the corrosion properties, with an emphasis on pitting resistance. The second part offers a perspective of some relevant modeling techniques available to simulate the corrosion of LPBF 316L SS, including current challenges that should be overcome.

    

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4. Benchmark Acetylene Binding Affinity and Separation through Induced Fit in a Flexible Hybrid Ultramicroporous Material

   https://doi.org/10.1002/anie.202106263  

   Shivanna, Mohana ; Otake, Ken‐ichi ; Song, Bai‐Qiao ; van Wyk, Lisa M. ; Yang, Qing‐Yuan ; Kumar, Naveen ; Feldmann, Wesley K. ; Pham, Tony ; Suepaul, Shanelle ; Space, Brian ; et al ( August 2021 , Angewandte Chemie International Edition)

   Structural changes at the active site of an enzyme induced by binding to a substrate molecule can result in enhanced activity in biological systems. Herein, we report that the new hybrid ultramicroporous material sql‐SIFSIX‐bpe‐Zn exhibits an induced fit binding mechanism when exposed to acetylene, C₂H₂. The resulting phase change affords exceptionally strong C₂H₂binding that in turn enables highly selective C₂H₂/C₂H₄and C₂H₂/CO₂separation demonstrated by dynamic breakthrough experiments. sql‐SIFSIX‐bpe‐Zn was observed to exhibit at least four phases: as‐synthesised (α); activated (β); and C₂H₂induced phases (β′ and γ). sql‐SIFSIX‐bpe‐Zn‐β exhibited strong affinity for C₂H₂at ambient conditions as demonstrated by benchmark isosteric heat of adsorption (Q_st) of 67.5 kJ mol⁻¹validated through in situ pressure gradient differential scanning calorimetry (PG‐DSC). Further, in situ characterisation and DFT calculations provide insight into the mechanism of the C₂H₂induced fit transformation, binding positions and the nature of host‐guest and guest‐guest interactions.

    

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5. Benchmark Acetylene Binding Affinity and Separation through Induced Fit in a Flexible Hybrid Ultramicroporous Material

   https://doi.org/10.1002/ange.202106263  

   Shivanna, Mohana ; Otake, Ken‐ichi ; Song, Bai‐Qiao ; van Wyk, Lisa M. ; Yang, Qing‐Yuan ; Kumar, Naveen ; Feldmann, Wesley K. ; Pham, Tony ; Suepaul, Shanelle ; Space, Brian ; et al ( August 2021 , Angewandte Chemie)

   Structural changes at the active site of an enzyme induced by binding to a substrate molecule can result in enhanced activity in biological systems. Herein, we report that the new hybrid ultramicroporous material sql‐SIFSIX‐bpe‐Zn exhibits an induced fit binding mechanism when exposed to acetylene, C₂H₂. The resulting phase change affords exceptionally strong C₂H₂binding that in turn enables highly selective C₂H₂/C₂H₄and C₂H₂/CO₂separation demonstrated by dynamic breakthrough experiments. sql‐SIFSIX‐bpe‐Zn was observed to exhibit at least four phases: as‐synthesised (α); activated (β); and C₂H₂induced phases (β′ and γ). sql‐SIFSIX‐bpe‐Zn‐β exhibited strong affinity for C₂H₂at ambient conditions as demonstrated by benchmark isosteric heat of adsorption (Q_st) of 67.5 kJ mol⁻¹validated through in situ pressure gradient differential scanning calorimetry (PG‐DSC). Further, in situ characterisation and DFT calculations provide insight into the mechanism of the C₂H₂induced fit transformation, binding positions and the nature of host‐guest and guest‐guest interactions.

    

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