336 results found
Varanasi RS, Lipińska-Chwałek M, Mayer J, et al., 2022, Mechanisms of austenite growth during intercritical annealing in medium manganese steels, Scripta Materialia, Vol: 206, ISSN: 1359-6462
The third-generation advanced high strength medium manganese (3–12 wt.%) steels typically consist of ultrafine-grained dual-phase (austenite-ferrite) microstructure, obtained through the intercritical annealing of martensite at temperatures typically ≤ 0.5Tmelt, where the bulk diffusion of Mn is extremely slow. Yet, the manganese partitioning plays a prominent role in the austenite growth from the martensitic matrix during this annealing step. Therefore, the ‘short circuit’ diffusion paths provided by grain boundaries (GBs) and dislocations must be crucial to the austenite growth. However, this influence is not well understood across the literature. In the present work, we study the mechanisms of austenite growth in a cold-rolled intercritically annealed medium manganese steel of composition Fe-10Mn-0.05C–1.5Al (wt.%). We provide evidence of manganese transport to austenite through GB diffusion, GB migration and dislocation pipe diffusion. Furthermore, the influence of GB misorientation on austenite growth is also reported.
Morgado FF, Katnagallu S, Freysoldt C, et al., 2021, Revealing atomic-scale vacancy-solute interaction in nickel (vol 203, 114036, 2021), SCRIPTA MATERIALIA, Vol: 205, ISSN: 1359-6462
Kühbach M, Kasemer M, Gault B, et al., 2021, Open and strong-scaling tools for atom-probe crystallography: high-throughput methods for indexing crystal structure and orientation, Journal of Applied Crystallography, Vol: 54, Pages: 1490-1508
<jats:p>Volumetric crystal structure indexing and orientation mapping are key data processing steps for virtually any quantitative study of spatial correlations between the local chemical composition features and the microstructure of a material. For electron and X-ray diffraction methods it is possible to develop indexing tools which compare measured and analytically computed patterns to decode the structure and relative orientation within local regions of interest. Consequently, a number of numerically efficient and automated software tools exist to solve the above characterization tasks. For atom-probe tomography (APT) experiments, however, the strategy of making comparisons between measured and analytically computed patterns is less robust because many APT data sets contain substantial noise. Given that sufficiently general predictive models for such noise remain elusive, crystallography tools for APT face several limitations: their robustness to noise is limited, and therefore so too is their capability to identify and distinguish different crystal structures and orientations. In addition, the tools are sequential and demand substantial manual interaction. In combination, this makes robust uncertainty quantification with automated high-throughput studies of the latent crystallographic information a difficult task with APT data. To improve the situation, the existing methods are reviewed and how they link to the methods currently used by the electron and X-ray diffraction communities is discussed. As a result of this, some of the APT methods are modified to yield more robust descriptors of the atomic arrangement. Also reported is how this enables the development of an open-source software tool for strong scaling and automated identification of a crystal structure, and the mapping of crystal orientation in nanocrystalline APT data sets with multiple phases.</jats:p>
Morgado FF, Katnagallu S, Freysoldt C, et al., 2021, Revealing atomic-scale vacancy-solute interaction in nickel, SCRIPTA MATERIALIA, Vol: 203, ISSN: 1359-6462
Liu C, Li Z, Lu W, et al., 2021, Reactive wear protection through strong and deformable oxide nanocomposite surfaces, NATURE COMMUNICATIONS, Vol: 12
Kovács A, Lewis LH, Palanisamy D, et al., 2021, Discovery and Implications of Hidden Atomic-Scale Structure in a Metallic Meteorite., Nano Lett
Iron and its alloys have made modern civilization possible, with metallic meteorites providing one of the human's earliest sources of usable iron as well as providing a window into our solar system's billion-year history. Here highest-resolution tools reveal the existence of a previously hidden FeNi nanophase within the extremely slowly cooled metallic meteorite NWA 6259. This new nanophase exists alongside Ni-poor and Ni-rich nanoprecipitates within a matrix of tetrataenite, the uniaxial, chemically ordered form of FeNi. The ferromagnetic nature of the nanoprecipitates combined with the antiferromagnetic character of the FeNi nanophases gives rise to a complex magnetic state that evolves dramatically with temperature. These observations extend and possibly alter our understanding of celestial metallurgy, provide new knowledge concerning the archetypal Fe-Ni phase diagram and supply new information for the development of new types of sustainable, technologically critical high-energy magnets.
Luo T, Serrano-Sanchez F, Bishara H, et al., 2021, Dopant-segregation to grain boundaries controls electrical conductivity of n-type NbCo(Pt)Sn half-Heusler alloy mediating thermoelectric performance, ACTA MATERIALIA, Vol: 217, ISSN: 1359-6454
Klaes B, Renaux J, Lardé R, et al., 2021, Analytical Three-Dimensional Field Ion Microscopy of an Amorphous Glass FeBSi., Microsc Microanal, Pages: 1-9
Three-dimensional field ion microscopy is a powerful technique to analyze material at a truly atomic scale. Most previous studies have been made on pure, crystalline materials such as tungsten or iron. In this article, we study more complex materials, and we present the first images of an amorphous sample, showing the capability to visualize the compositional fluctuations compatible with theoretical medium order in a metallic glass (FeBSi), which is extremely challenging to observe directly using other microscopy techniques. The intensity of the spots of the atoms at the moment of field evaporation in a field ion micrograph can be used as a proxy for identifying the elemental identity of the imaged atoms. By exploiting the elemental identification and positioning information from field ion images, we show the capability of this technique to provide imaging of recrystallized phases in the annealed sample with a superior spatial resolution compared with atom probe tomography.
Rau JS, Balachandran S, Schneider R, et al., 2021, High diffusivity pathways govern massively enhanced oxidation during tribological sliding, Acta Materialia, Pages: 117353-117353, ISSN: 1359-6454
Liu C, Garner A, Zhao H, et al., 2021, CALPHAD-informed phase-field modeling of grain boundary microchemistry and precipitation in Al-Zn-Mg-Cu alloys, ACTA MATERIALIA, Vol: 214, ISSN: 1359-6454
Volz N, Xue F, Zenk CH, et al., 2021, Understanding creep of a single-crystalline Co-Al-W-Ta superalloy by studying the deformation mechanism, segregation tendency and stacking fault energy, ACTA MATERIALIA, Vol: 214, ISSN: 1359-6454
Ener S, Skokov KP, Palanisamy D, et al., 2021, Twins - A weak link in the magnetic hardening of ThMn12-type permanent magnets, ACTA MATERIALIA, Vol: 214, ISSN: 1359-6454
Gault B, Poplawsky JD, 2021, Correlating advanced microscopies reveals atomic-scale mechanisms limiting lithium-ion battery lifetime (vol 12, 3740, 2021), NATURE COMMUNICATIONS, Vol: 12, ISSN: 2041-1723
Sun B, Lu W, Gault B, et al., 2021, Chemical heterogeneity enhances hydrogen resistance in high-strength steels, NATURE MATERIALS, ISSN: 1476-1122
Souza Filho IR, Ma Y, Kulse M, et al., 2021, Sustainable steel through hydrogen plasma reduction of iron ore: Process, kinetics, microstructure, chemistry, ACTA MATERIALIA, Vol: 213, ISSN: 1359-6454
Johny J, Prymak O, Kamp M, et al., 2021, Multidimensional thermally-induced transformation of nest-structured complex Au-Fe nanoalloys towards equilibrium, NANO RESEARCH, ISSN: 1998-0124
Gault B, Poplawsky JD, 2021, Correlating advanced microscopies reveals atomic-scale mechanisms limiting lithium-ion battery lifetime, NATURE COMMUNICATIONS, Vol: 12, ISSN: 2041-1723
Lilensten L, Kostka A, Lartigue-Korinek S, et al., 2021, Partitioning of Solutes at Crystal Defects in Borides After Creep and Annealing in a Polycrystalline Superalloy, JOM, Vol: 73, Pages: 2293-2302, ISSN: 1047-4838
Kim S-H, Zhang X, Ma Y, et al., 2021, Influence of microstructure and atomic-scale chemistry on the direct reduction of iron ore with hydrogen at 700 degrees C, ACTA MATERIALIA, Vol: 212, ISSN: 1359-6454
Nucleation and growth of Ti3Alα2ordered domains inα-Ti–Al–X alloys were characterised using a combination of transmission electronmicroscopy, atom probe tomography and small angle X-ray scattering. Model alloys based on Ti–7Al (wt.%) and containing O, V and Mowere aged at 550◦C for times up to 120 d and the resulting precipitate dispersions were observed at intermediate points. Precipitates grewto around 30 nm in size, with a volume fraction of 6–10% depending on tertiary solutes. Interstitial O was found to increase the equilibriumvolume fraction ofα2, while V and Mo showed relatively little influence. Addition of any of the solutes in this study, but most prominentlyMo, was found to increase nucleation density and decrease precipitate size and possibly coarsening rate. Coarsening can be described by theLifshitz-Slyozov-Wagner model, suggesting a matrix diffusion-controlled coarsening mechanism (rather than control by interfacial coherency).Solutionising temperature was found to affect nucleation number density with an activation energy ofEf=1.5±0.4 eV, supporting the hypothesisthat vacancy concentration affectsα2nucleation. The observation that all solutes increase nucleation number density is also consistent with avacancy-controlled nucleation mechanism.
Palanisamy D, Kovacs A, Hegde O, et al., 2021, Influence of crystalline defects on magnetic nanodomains in a rare-earth-free magnetocrystalline anisotropic alloy, PHYSICAL REVIEW MATERIALS, Vol: 5, ISSN: 2475-9953
Schwarz TM, Dietrich CA, Ott J, et al., 2021, 3D sub-nanometer analysis of glucose in an aqueous solution by cryo-atom probe tomography, SCIENTIFIC REPORTS, Vol: 11, ISSN: 2045-2322
Koprek A, Zabierowski P, Pawlowski M, et al., 2021, Effect of Cd diffusion on the electrical properties of the Cu(In,Ga)Se2 thin-film solar cell, Solar Energy Materials and Solar Cells, Vol: 224, Pages: 1-10, ISSN: 0927-0248
Cu(In,Ga)Se2 (CIGSe)-based solar cells are promising candidates for efficient sunlight harvesting. However, their complex composition and microstructure can change under operation conditions, for instance heating from sun light illumination can lead to a degradation in performance. Here, we investigate the thermally-induced degradation processes in a set of CIGSe-based solar cells that were annealed at temperatures between 150 °C and 300 °C. Using correlative atom probe tomography (APT)/transmission electron microscope (TEM), we found that the buffer/absorber interface is not sharp but consists of an interfacial zone (2–6.5 nm wide) where a gradient of constituent elements belonging to the CdS buffer and CIGSe absorber appears. An enhanced short-range Cd in-diffusion inside the CIGSe was observed whenever a low Ga/(Ga + In) ratio (≤ 0.15) occurred at the interface. This might indicate the presence of Ga vacancies as a channeling defect for Cd in-diffusion inside the CIGSe layer leading to a buried p/n-homojunction. We evidence that a considerable amount of Cd is found inside the CIGSe layer at annealing temperatures higher than 150 °C. Further investigations of the elemental redistribution inside the CIGSe layer combined with C–V measurements support the formation of CdCu + donor like defects deep inside the p-type CIGSe which lead to a strong compensation of the CIGSe layer and hence to strong deterioration of cell efficiency at annealing temperatures higher than 200 °C. Hence, understanding the degradation processes in Cu(In,Ga)Se2 (CIGSe)-based solar cells opens new opportunities for further improvement of the long-term device performance.
Tsai S-P, Makineni SK, Gault B, et al., 2021, Precipitation formation on Sigma 5 and Sigma 7 grain boundaries in 316L stainless steel and their roles on intergranular corrosion, ACTA MATERIALIA, Vol: 210, ISSN: 1359-6454
Luo T, Kuo JJ, Griffith KJ, et al., 2021, Nb-Mediated Grain Growth and Grain-Boundary Engineering in Mg3Sb2-Based Thermoelectric Materials, ADVANCED FUNCTIONAL MATERIALS, Vol: 31, ISSN: 1616-301X
Kante S, Kuernsteiner P, Motylenko M, et al., 2021, Eutectoid growth of nanoscale amorphous Fe-Si nitride upon nitriding, ACTA MATERIALIA, Vol: 209, ISSN: 1359-6454
Im HJ, Makineni SK, Oh C-S, et al., 2021, Elemental Sub-Lattice Occupation and Microstructural Evolution in γ/γ' Co-12Ti-4Mo-Cr Alloys., Microsc Microanal, Pages: 1-5
We report on comparative atom probe tomography investigations of γ/γ′-forming Co–12Ti–4Mo–Cr alloys. Moderate additions of Cr (2 and 4 at%) reduced the γ/γ′ lattice misfit and increased the γ′ volume fraction of a Co–12Ti–4Mo alloy significantly. These microstructural changes were accompanied by changes in the elemental partitioning between γ and γ′ and site-occupancy in γ′. Spatial distribution maps revealed that Mo occupied both Co and Ti sub-lattice sites in γ′. In agreement with the experimental data, thermodynamic calculations predicted a stronger tendency for Mo to occupy the Co-sites than for Cr and an increase in Cr fraction on the Ti-sites with increasing Cr content.
Zhou X, Mianroodi JR, da Silva AK, et al., 2021, The hidden structure dependence of the chemical life of dislocations, SCIENCE ADVANCES, Vol: 7, ISSN: 2375-2548
Medrano S, Zhao H, Gault B, et al., 2021, A model to unravel the beneficial contributions of trace Cu in wrought Al–Mg alloys, Acta Materialia, Vol: 208, Pages: 1-12, ISSN: 1359-6454
The softening and strengthening contributions in pre-deformed and aged Al–Mg–Cu alloys containing 3 wt.%Mg and 0.5 wt.%Cu are evaluated by a combination of microscopy, mechanical testing and modelling. A refined phenomenological model for the work hardening response, accounting for the separate effects of recovery and precipitation, is shown to be suitable for an unambiguous determination of the precipitation hardening contribution in these alloys. Significantly, it is found that the mechanical response of these alloys is not strongly impacted by Cu content (in the low Cu content regime), pre-deformation level or aging temperature meaning that the alloys are robust with respect to variations in composition. This is interesting from the perspective of alloy design concepts based on ‘recycling friendly’ compositions in applications that include paint-baking.
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