@article {1566, title = {Serial sectioning in the SEM for three dimensional materials science}, journal = {Current Opinion in Solid State and Materials Science}, year = {2020}, pages = {100817}, abstract = {

Here we explore the range of serial sectioning techniques that have evolved over the past decade, providing a comprehensive toolkit for capturing rich 3D microstructures, chemistries and crystallographic information, with sub-micron resolution at volumes that extend out to mm3 or even cm3. In each case we consider the challenges associated with their application, the volumes they can analyze, the damage to the surface they impart, and their suitability for different materials. In certain cases these warrant hybrid methods, motivating workflows that leverage multiple sectioning modes within the same instrument. Finally, we provide a perspective on their future development, including advances in data collection, segmentation, registration, data fusion, and correlative microscopy. Furthermore, the exploitation of 3D techniques for a better understanding of existing materials, and the design of new ones, is discussed through their use in multiscale modelling, digital twinning, material informatics and machine learning frameworks.

}, keywords = {Biology, Life sciences, Materials science, Scanning electron microscopy, Serial sectioning}, issn = {13590286}, doi = {10.1016/j.cossms.2020.100817}, url = {https://doi.org/10.1016/j.cossms.2020.100817}, author = {Echlin, Mclean P. and Burnett, Timothy L. and Polonsky, Andrew T. and Pollock, Tresa M. and Withers, Philip J.} } @article {1406, title = {Solidification-driven orientation gradients in additively manufactured stainless steel}, journal = {Acta Materialia}, volume = {183}, year = {2020}, pages = {249{\textendash}260}, abstract = {

A sample of 304L stainless steel manufactured by Laser Engineered Net Shaping (LENS) was characterized in 3D using TriBeam tomography. The crystallographic, structural, and chemical properties of the as-deposited microstructure have been studied in detail. 3D characterization reveals complex grain morphologies and large orientation gradients, in excess of 10o, that are not easily interpreted from 2D cross-sections alone. Misorientations were calculated via a methodology that locates the initial location and orientation of grains that grow during the build process. For larger grains, misorientation increased along the direction of solidification. For grains with complex morphologies, K-means clustering in orientation space is demonstrated as a useful approach for determining the initial growth orientation. The gradients in misorientation directly tracked with gradients in chemistry predicted by a Scheil analysis. The accumulation of misorientation is linked to the solutal and thermal solidification path, offering potential design pathways for novel alloys more suited for additive manufacturing.

}, keywords = {Additive manufacturing, Microstructure, Solidification, Tomography, Tribeam}, issn = {13596454}, doi = {10.1016/j.actamat.2019.10.047}, author = {Polonsky, Andrew T. and Lenthe, William C. and Echlin, Mclean P. and Livescu, Veronica and Gray, George T. and Pollock, Tresa M.} } @article {1561, title = {Structural coupling and magnetic tuning in Mn$_{2}$$_{-}$ₓCoₓP magnetocalorics for thermomagnetic power generation}, journal = {APL Materials}, volume = {8}, year = {2020}, pages = {041106}, abstract = {

Promising materials for magnetic refrigeration and thermomagnetic power generation often display strong coupling between magnetism and structure. It has been previously proposed that MnCoP exhibits this strong coupling, contributing to its substantial magnetocaloric effect near TC = 578K. Here, we show from temperature-dependent synchrotron x-ray diffraction that MnCoP displays a discontinuity in the thermal expansion at TC, with spontaneous magnetostriction that is positive in the a direction and negative in the b direction, highlighting the anisotropic nature of the magnetostructural coupling. Varying the Mn:Co ratio of Mn2-xCoxP within the range of 0.6 \≤ x \≤ 1.4 allows the magnetic properties to be tuned. TC decreases as the composition deviates from stoichiometric MnCoP, as does the saturation magnetization. The magnitude of the magnetocaloric effect, |\ΔSM|, decreases as well, due to broadening of the magnetic transition. The large reversible change in magnetization \ΔM accessible over a small temperature range under moderate magnetic fields makes these materials promising for thermomagnetic power generation from waste heat.

}, issn = {2166532X}, doi = {10.1063/1.5142000}, url = {https://doi.org/10.1063/1.5142000}, author = {Levin, Emily E. and Bocarsly, Joshua D. and Grebenkemper, Jason H. and Issa, Ramsey and Wilson, Stephen D. and Pollock, Tresa M. and Seshadri, Ram} } @article {1621, title = {Sustainability through alloy design: Challenges and opportunities}, journal = {Progress in Materials Science}, year = {2020}, pages = {100722}, abstract = {

Exciting metallurgical breakthroughs of the last decades alongside the development and wide-ranging availability of new and more capable experimental and theoretical tools for metals research demonstrate that we are witnessing the dawn of a new age in metals design. Historically, the discovery of new metallic materials has enabled the vast majority of the key engineering advances in human history. Current engineering challenges create an urgent need for new metallic materials to further our technological advances in multiple industries that are key to our existence. Yet, present data on metals processing clearly demonstrate the significant environmental impact of the metallurgical industry on our planet\&$\#$39;s future. There are numerous reports in which this impact and corresponding processing solutions are discussed. On the other hand, design of new metallic materials with improved property combinations can help address key environmental challenges in various ways. To this end, the goal of this review is to discuss the most urgent sustainability challenges that can be addressed with alloy design, to help orchestrate the increasing interest in metallurgical research to focus on these most critical challenges.

}, keywords = {Aluminum, High Entropy Alloys, Magnesium, Metallurgy, Shape memory alloys, Steel, Superalloys, Sustainability, Titanium}, issn = {00796425}, doi = {10.1016/j.pmatsci.2020.100722}, url = {https://doi.org/10.1016/j.pmatsci.2020.100722}, author = {Cann, Jaclyn L. and De Luca, Anthony and Dunand, David C. and Dye, David and Miracle, Daniel B. and Oh, Hyun Seok and Olivetti, Elsa A. and Pollock, Tresa M. and Poole, Warren J. and Yang, Rui and Tasan, C. Cem} } @article {1496, title = {Short crack propagation from cracked non-metallic inclusions in a Ni-based polycrystalline superalloy}, journal = {Acta Materialia}, volume = {165}, year = {2019}, pages = {241{\textendash}258}, abstract = {

Fatigue cracks initiating from surface and sub-surface non-metallic inclusions (NMIs) have recently been demonstrated to be a necessary but not sufficient explanation for atypically short low-cycle fatigue life in Inconel 718 alloy at intermediate temperature. Therefore, the early stages of short crack propagation from surface NMIs were investigated in a crystallographic and two-dimensional versus three-dimensional morphological manner after room temperature low cycle fatigue (LCF) testing. In the present investigation, NMIs were purposely pre-cracked using different techniques to suppress the natural crack initiation period and thus the incubation period prior to the early stages of crack propagation. Under such fatigue testing conditions, different mechanisms of crack transmission from pre-cracked NMIs were identified: (i) no propagation, (ii) NMI/adjacent metallic grain interfacial debonding, (iii) transgranular crack propagation within the adjacent metallic grain. Focused-ion-beam cross-section observations of numerous fatigue tested NMIs aimed to define a morphological criterion for non-propagating NMIs. Large cracked NMIs at the surface (2c) with limited extension into the depth (a) did not propagate under such fatigue conditions for 2c/a ratio higher than 3. Furthermore, specific crystallographic relationships between NMIs and the adjacent metallic grain explained different crack propagation configurations from pre-cracked NMIs, i.e. interfacial debonding and transgranular crack propagation involving single or multiple-slip activity.

}, keywords = {Focus-ion-beam cross-section (FIB-cross section), Low cycle fatigue, Non-metallic inclusions, Short crack propagation, Superalloy 718DA}, issn = {13596454}, doi = {10.1016/j.actamat.2018.11.051}, author = {Texier, Damien and Stinville, Jean Charles and Echlin, Mclean P. and Pierret, St{\'e}phane and Villechaise, Patrick and Pollock, Tresa M. and Cormier, Jonathan} }