Oleg Usoltsev | Searcharxiv

arXiv2026

Nanoscale mapping of phase-transformation pathways in medium-Mn TRIP steel by multimodal STEM

The mechanical response of third-generation advanced high-strength steels is governed by phase transformations at the nanoscale, yet the coupled evolution of chemistry and crystallography remains poorly resolved. Here we apply a correlative scanning transmission electron microscopy approach that enables simultaneous mapping of lattice structure, crystallographic orientation, and phase distribution at 10 nanometre resolution in a medium-manganese TRIP steel. We combine nano-beam electron diffraction and energy-dispersive X-ray spectroscopy maps to characterize an industrial medium-manganese steel containing 7.15 weight percent Mn. Tensile testing of a rolled steel sample was performed, and lamellae were extracted from deformed and undeformed regions. Manganese-resolved energy-dispersive X-ray spectroscopy provides a chemical fingerprint that, when combined with nano-beam electron diffraction based phase segmentation, enables robust ferrite-martensite separation and phase-resolved lattice-parameter refinement. The phase fractions of ferrite, austenite, and martensite are quantified together with their corresponding lattice parameters, accompanied by measurable shifts in grain-size distributions and crystallographic texture in the deformed regions. Kernel average misorientation maps reveal systematically lower local misorientation in ferrite than in martensite. This multimodal workflow provides a transferable framework for quantitative, phase-resolved analysis of complex multiphase alloys at the nanoscale.

cond-mat.mtrl-sci↗

arXiv2024

Unveiling the local elemental arrangements across the interfaces inside CdSe/Cd1-xZnxS core-shell and CdSe/CdS/ Cd1-xZnxS core-crown-shell quantum wells

We report on a systematic study of the Cd, Zn, Se, and S elemental distributions across the interfaces in CdSe/Cd1-xZnxS core-shell and CdSe/CdS/Cd1-xZnxS core-crown-shell quantum wells with the CdSe core thickness ranging from 3.5 to 5.5 ML. By processing the XAS data, we observe that the Cd-Se bonds dominate at the CdSe/Cd1-xZnxS core-shell interface of structures with the 3.5 ML cores, while the Cd-Se bonds were more abundant in the cases of the 4.5 and 5.5 ML cores. The complementary information about prevailing bonds were extracted for other constituting elements, thus, describing the distribution of the elements at the core-shell interface of CdSe-based NPLs. The naked CdSe cores are covered with an organic shell via bridging oxygen atoms. Also, we address the issue of stability of such core-shell systems over the time. We demonstrate that after a half year of aging of the commercial-ready 4.5 ML CdSe/CdxZn1-xS NPLs, the Cd-Se bonds become more evident due to the partial degradation of the Cd-S bonds. This is the first experimental assessment of prevailing interatomic bonds at the core-shell interface in the CdSe-based NPLs of incremental structural heterogeneity, providing factual evidences about the elemental arrangement inside the core-crown-shell NPLs and the growth path of crowns and shells.

cond-mat.mtrl-sci↗