arXiv subjects

Petr Svora

Publications and source records attributed to Petr Svora.

4 recordsLinked to original sources

arXiv2025

Effect of cold rolling strain on the microstructural evolution in equimolar MoNbTaTiZr refractory complex concentrated alloy: Comprehensive characterization

This work presents a pilot study on a strained complex concentrated alloy based on refractory elements: MoNbTaTiZr. Initially, the as-cast and homogenization-annealed conditions were characterized. After casting, the alloy consists of two solid solutions with BCC 1 and BCC 2 crystal structures. Homogenization annealing promotes the growth, ordering, and refinement of the BCC 2 phase. TEM and AES analyses indicate possible Zr segregation at grain boundaries in the as-cast state. In contrast, annealing followed by cooling results in the formation of Ti-Zr-based particles without segregation. Subsequently, the annealed alloy was cold-rolled, and its microstructure was investigated. During rolling, grain fragmentation occurs within the structure. In addition to the two BCC solid solutions, a phase with an FCC crystal structure is identified after rolling. Its composition corresponds to the Zr2Ta phase, which is a Laves phase of the A2B type. Rotational relationships, relatively rare in rolled materials with BCC structures, are identified. The texture components found after 10% rolling deformation are related to that present after 20% deformation by a 45 degrees <110> rotation, and this component is related to that appearing after 30% deformation by a 20 degrees <100> rotation. However, no distinct rolling texture or clear texture development was observed, although some mutual relationships among preferred orientations can be identified. Schmid and Taylor factor maps demonstrate that, despite deformation, the alloy remains capable of further strain accumulation and plastic deformation. Twinning is also observed after rolling, which may be beneficial, as deformation twinning contributes to improved ductility in the alloy.

cond-mat.mtrl-sci↗

arXiv2024

The influence of nitrogen ion implantation on the microstructure and chemical composition of a thin layer on the biodegradable Zn-0.8Mg-0.2Sr substrate

In this research, the influence of the N+ ion implantation process on the microstructure of a biodegradable Zn-0.8Mg-0.2Sr alloy was investigated using various experimental techniques. Microscopic analysis revealed that a fluence of 17x10^17 ions/cm^2 resulted in the oversaturation of pure Zn and Mg2Zn11 surfaces, leading to the formation of nano/micro-porous layers up to 400 nm thick. The behavior of the Zn-0.8Mg-0.2Sr alloy was observed to be similar to that of the individual pure phases, albeit without the creation of pore structures. A limited formation of MgO and Mg3N2 was observed on the alloy surface, although the overall presence of Mg significantly increased from 0.8 to 15 wt.%. This increase was caused by the decomposition of the Mg2Zn11 phase during the process and subsequent diffusion of Mg toward the surface. The absence of Zn3N2 within the samples could be explained by the thermodynamic instability and low Zn-N affinity. Despite the absence of zinc nitride, GD-OES confirmed 10 at. % of nitrogen in the pure zinc, suggesting a possible accommodation of N atoms in the interstitial positions. This study points out to the complex nature of the process and highlights other promising directions for future research.

cond-mat.mtrl-sci↗

arXiv2024

Advantages of rapid solidification over casting of Mg-0.4Zn-1Y alloy

The Mg-Y-Zn magnesium alloy system is commonly recognized for its remarkable combination of high strength and ductility, achieved even with minimal amounts of alloying elements. This exceptional performance is attributed to its unique microstructure, which includes Long-Period Stacking Ordered (LPSO) phases or the distinctive microstructure derived from the LPSO phase, referred to as the Mille-Feuille structure (MFS). This study systematically compares the traditional ingot metallurgy method with the rapid solidification technique, coupled with diverse heat treatments and extrusion processes. Microscopic analyses reveal variations in the presence of LPSO phases, Mille-Feuille structure, and grain size, leading to divergent mechanical and corrosion properties. The rapid solidification approach stands out, ensuring superior mechanical properties alongside a reasonable corrosion rate.

cond-mat.mtrl-sci↗

arXiv2023

Quantitative three-dimensional local order analysis of nanomaterials through electron diffraction

Structure-property relationships in ordered materials have long been a core principle in materials design. However, the intentional introduction of disorder into materials provides structural flexibility and thus access to material properties that are not attainable in conventional, ordered materials. To understand disorder-property relationships, the disorder - i.e., the local ordering principles - must be quantified. Correlated disorder can be probed experimentally by diffuse scattering. The analysis is notoriously difficult, especially if only powder samples are available. Here, we combine the advantages of three-dimensional electron diffraction - a method that allows single crystal diffraction measurements on sub-micron sized crystals - and three-dimensional difference pair distribution function analysis (3D-{\Delta}PDF) to address this problem. 3D-{\Delta}PDFs visualise and quantify local deviations from the average structure and enable a straightforward interpretation of the single crystal diffuse scattering data in terms of a three-dimensional local order model. Comparison of the 3D-{\Delta}PDF from electron diffraction data with those obtained from neutron and x-ray experiments of yttria-stabilized zirconia demonstrates the reliability of the newly proposed approach.

cond-mat.mtrl-sci↗