Effect of high-temperature exposure on the microstructure and mechanical properties of the Al5Ti5Co35Ni35Fe20 high-entropy alloy

Effect of high-temperature exposure on the microstructure and mechanical properties of the Al5Ti5Co35Ni35Fe20 High-Entropy Alloy was studied. High-entropy alloys belong to the group of multi-principal element alloys composed of at least five elements with a concentration between 5 and 35 atomic pct. Despite the multicomponent composition, the goal is to achieve a simple solid solution. The alloy was exposed to a temperature range of 650-900 degrees C for 168 h (7 days), after hot rolling and air-quenching. After hot rolling the investigated alloy was not fully supersaturated. The application of air cooling caused gamma' precipitation, which was uniformly distributed within the microstructure. High-temperature exposure caused the growth of gamma' particles. At 700 degrees C and higher, additional continuous and discontinuous precipitation of gamma' was observed. Finally, the microstructure of the investigated alloy consisted of gamma matrix and three types of gamma' precipitates, i.e. spherical gamma' phases with bimodal distribution within the grains and elongated DP gamma' phases present at the grain boundaries. The highest mechanical properties were obtained after exposure to 650 degrees C, which was caused by gamma' precipitation. Further increase in temperature decreased the mechanical properties.Web of Science9155955

Effect of polyaniline content and protonating dopants on electroconductive composites

Elastic constructive elements prepared by electrospinning using polyacrylonitrile/polyaniline (PAN/PANI) electroconductive composites were prepared and investigated in terms of their thermal and mechanical properties. This study was focused on the impact of the type of counterion of polyaniline and the PANI content in composites on the thermal, conductive and morphological properties of electrospun fibers. In this study, composites obtained from PANI doped with sulfuric acid showed the highest conductivity, and composites obtained from PANI doped with hydrochloric acid showed the highest thermal stability. All obtained composites exhibited good thermal stability, with T5 values in the range of 230–268 °C that increased with increasing PANI content. The prepared composites exhibited comparable PAN Tg values, which indicates their suitability for processing. Instrumental analysis of polymers and composites was carried out using UV–visible spectroscopy, thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical thermal analysis and scanning electron microscopy

The struggle of Iraqi and Syrian Kurds against the Islamic State from 2014 to 2018

W pracy magisterskiej przedstawione zostały działania kurdyjskich formacji militarnych z Iraku i Syrii, które były wymierzone przeciwko Państwu Islamskiemu. Praca obejmuje lata 2014 - 2018. Autor podejmuje próbę pokazania kurdyjskich formacji militarnych zarówno z historycznego punktu widzenia jak i w ujęciu współczesnym. W pracy poruszone są ponadto takie aspekty zmagań Kurdów z Państwem Islamskim jak relacje międzynarodowe oraz udział kobiet w działaniach wojennych.The MA thesis describes actions of Kurdish militias from Iraq and Syria that were aimed against the Islamic State. The dissertation includes a period from 2014 to 2018. The author tries to present Kurdish militias from the historical point of view and regarding contemporary situation as well. Thesis depicts also such attributes of Kurdish struggle against the Islamic State as international relations and participation of women in military activities

Symbol of wine in classical Persian poetry from the seventh to the fourteenth century on the basis of selected examples

Wino było ważne dla perskich poetów, a efektem tego zamiłowania do pisania o winie jest jegoczęsta obecność w klasycznej poezji perskiej. Uprawa winorośli oraz spożycie wina w Persji byłyznane od najdawniejszych czasów, a w późniejszym okresie do Iranu zaczęło trafiać też wino, którebyło importowane z innych krajów, np. z Francji. W literaturze perskiej wyróżnia się nurtykhamriye i sāqināme, które skupione są na kwestiach związanych z winem. Nazwa pierwszego znich wywodzi się od arabskiego słowa khamr oznaczającego wino i nurt ten jest reprezentowanyprzez utwory przynależące do różnych form poetyckich. Sāqināme jest natomiast nurtem, któregobohaterem jest sāqi (podczaszy). Tematyka utworów omawianych w pracy jest różnorodna.Znajdują się tu zarówno opisy produkcji wina (Mādar-e mey Rudakiego) jak i dysputy prowadzoneprzez wino (Gol o mol Zangi Buchariego). Innymi poetami mającymi w swym dorobku tego typudzieła są m.in. Hafez czy Manuczehri.Wine was important thing for Persian poets and frequent presence of wine’s symbol in classicalPersian poetry is an effect of poets’ fondness for writing about it. Viniculture and drinking winewere known in Persia from old times and then Iranians have begun to import wine from othercountries like France. Among poems of Persian literature we can single out two poetic genreskhamriye and sāqināme that are focused on issues related to wine. The first of them has name that isderived from arabic word khamr (wine) and is represented by poems that belong to many poeticalforms. On the other hand in sāqināme cupbearer is the literary character of poem. Literary worksthat were selected for this thesis raise a lot of topics. There are both descriptions of production ofwine (Rudaki’s Mādar-e mey) and debates with the participation of wine (Zangi Bukhari’s Gol omol). The other poets that have been writing in such a manner are also known – for example Hafizand Manuchihri

Fine-tuning of mechanical properties in a Zn–Ag–Mg alloy via cold plastic deformation process and post-deformation annealing

In recent years, Zn-based materials have been extensively investigated as potential candidates for biodegradable implant applications. The introduction of alloying elements providing solid-solution strengthening and second phase strengthening seems crucial to provide a suitable platform for the thermo-mechanical strengthening of Zn alloys. In this study, a systematic investigation of the microstructure, crystallographic texture, phase composition, and mechanical properties of a Zn–3Ag-0.5Mg (wt%) alloy processed through combined hot extrusion (HE) and cold rolling (CR), followed by short-time heat treatment (CR + HT) at 200 °C was conducted. Besides, the influence of different annealing temperatures on the microstructure and mechanical properties was studied. An adequate combination of processing conditions during CR and HT successfully addressed brittleness obtained in the high-strength HE Zn–3Ag-0.5Mg alloy. By controlling the microstructure, the most promising results were obtained in the sample subjected to 50% CR reduction and 5-min annealing, which were: ultimate tensile strength of 432 MPa, yield strength of 385 MPa, total elongation to failure of 34%, and Vickers microhardness of 125 HV0.3. The obtained properties clearly exceed the mechanical benchmarks for biodegradable implant materials. Based on the conducted investigation, brittle multi-phase Zn alloys' mechanical performance can be substantially enhanced to provide sufficient plasticity by grain refinement through cold deformation process, followed by short-time annealing to restore proper strength

Microstructure and mechanical properties of a Zn-0.5Cu alloy processed by high-pressure torsion

The microstructure, texture and mechanical properties of a quasi-single-phase Zn-0.5Cu (wt. %) alloy processed by high-pressure torsion (HPT) for up to 10 turns were investigated using electron backscatter diffraction (EBSD), Vickers hardness measurements and uniaxial tensile tests. The results show that during torsional straining there is dynamic recrystallization, subgrain refinement, a dissolution of ε – Zn4Cu precipitates and solid-solution strengthening. Monotonic deformation develops a strong {0001}〈112ത0〉 local texture instead of the characteristic basal fiber texture. Sharp texture and misorientation angles for all grain boundaries of < 30° causes significantly higher yield stress and ultimate tensile stress compared to processing of the alloy by equal-channel angular pressing

Determination of critical resolved shear stresses associated with <a> slips in pure Zn and Zn-Ag alloys via micro-pillar compression

The room-temperature plastic deformation behavior of pure Zn and Zn-Ag (0–2.2 at.%) biodegradable alloys has been investigated via uniaxial in situ micro-pillar compression tests performed within a scanning electron microscope. The critical resolved shear stresses (CRSS) were quantified as a function of micro-pillar diameter. The compression of single crystal micro-pillars was performed at various strain rates in carefully selected grains, the crystallographic orientation of which facilitates deformation either via basal 0001〈112¯0〉 or prismatic 101¯0〈112¯0〉 slip. The CRSS values increased with decreased micro-pillar diameter, revealing a more pronounced size effect in pure Zn deformed via basal slip. The observed solid solution strengthening effect in Zn-Ag alloys with increasing Ag content was associated with a CRSS increase from 26.6 MPa to 37.0 MPa (by ∼ 40 %) in the basal slip system and from 99.1 MPa to 188.4 MPa (by ∼ 104 %) in the prismatic slip system. The extraordinarily high CRSS values for basal slip activated in pure Zn and Zn-0.14Ag alloy compared to the solid solution strengthening model was attributed to the critically low dislocation density. In the Zn-Ag alloy with Ag content > 0.5 at.% higher dislocation densities are expected, which result in a more predictable plastic deformation behavior

Abnormal grain growth in a Zn-0.8Ag alloy after processing by high-pressure torsion

Abnormal grain growth (AGG) in a Zn-0.8Ag (wt%) alloy, produced through the application 12 of high-pressure torsion (HPT), was systematically investigated using scanning electron 13 microscopy (SEM), electron backscattered diffraction (EBSD), high-resolution transmission 14 electron microscopy (HR-TEM) and microhardness testing. The HPT-deformed alloy 15 exhibits AGG at room temperature without any additional heat treatment. Analysis by EBSD 16 revealed oriented grain nucleation in a {112ത0}〈0001〉 direction from the initial (0001) fibre 17 texture which agrees with the maximum energy release model. New grains were oriented 18 according to the minimal Young’s modulus direction (c-axis), parallel to the shearing 19 direction. The strain-induced dissolution of nanocrystalline Zn3Ag precipitates was identified 20 as the main driving force for AGG in this alloy. The strains necessary for the initiation and 21 termination of AGG were determined as ~4.0 and ~5.0, respectively. The increase in solid-22 solution strengthening caused an increase in hardness from ~47 HK in the fine-grained centre 23 to ~84 HK in the coarse-grained region. A Hall-Petch investigation revealed grain refinement 24 softening below a grain size of 23 μm. These results provide the first comprehensive 25 description of AGG in metallic materials processed by a severe plastic deformation method 26 at room temperature