In this work, the effect of equal channel angular pressing (ECAP) on the microstructure and mechanical properties of zinc and zinc alloys with Ag, Cu, and Mn additions (0.5 at%) was investigated. ...Four passes of ECAP Route BC was performed at room temperature for each material. Properties of investigated materials after ECAP were compared to their coarse grained counterparts obtained via indirect hot extrusion at 300 °C. Highest strengthening effect was observed for alloy containing the Mn addition. Grain refinement in materials after ECAP was obtained, mean grain diameter is equal to 20 µm in the case of pure zinc, and less than 3.2 µm for alloys. Strain rate dependent plasticity increase was observed for all fine grained materials, with maximum elongation of 510% measured for Zn-Cu alloy after ECAP. Grain refinement did not result in increased yield and ultimate tensile strength of alloys after ECAP. In all investigated materials tensile properties after ECAP were 20 ~ 60% lower than in hot extruded samples. Based on the tensile properties, microstructure and texture analysis, the changes in the main deformation mechanisms were considered. It was presented that the crystallographic texture and grain size are the main factors affecting twinning, slip and non-slip deformation mechanisms resulting in large differences in observed mechanical properties.
The Zn-0.5Cu alloy was investigated in as-cast, homogenized state and after carrying out equal channel angular pressing four times at room temperature via route BC. Microstructure analysis using ...light microscopy and SEM/EBSD was performed, as well as tensile tests, misorientation angle distribution and texture analysis. The initial microstructure with the average grain size of 560 µm was refined to a grain size of approx. 1 µm. The obtained microstructure consists of uniaxial grains separated mostly by high angle grain boundaries. Mechanical characterization was performed at strain rates from 2 × 10−6 s−1 to 1 s−1 at room temperature. Ultrafine-grained zinc-copper alloy exhibited 510% elongation with the strain rate sensitivity equal 0.31, which was the first observation of room temperature superplasticity in Zn-Cu alloys. Based on the microstructure, misorientation angle and texture analysis, the main operating deformation mechanisms were distinguished for samples deformed at strain rates from 2 × 10−5 s−1 to 10−1 s−1.
Fine-grained Zn-0.8Ag alloy processed by equal channel angular pressing (ECAP) presents elongation over 650% and strain rate sensitivity 0.45 at room temperature. Examination along three orthogonal ...directions shows minimal superplastic anisotropy both under tension and compression. Measured tension-compression yield stress asymmetry indicates much easier grain boundary sliding under tension than compression.
Large‐scale computing and data processing with cloud resources is gaining popularity. However, the usage of the cloud differs from traditional high‐performance computing (HPC) systems and both ...algorithms and codes have to be adjusted. This work is often time‐consuming and performance is not guaranteed. To address this problem we have developed the PCJ library (parallel computing in Java), a novel tool for scalable HPC and big data processing in Java. In this article, we present a performance evaluation of parallel applications implemented in Java using the PCJ library. The performance evaluation is based on the examples of highly scalable applications of different characteristics focusing on CPU, communication or I/O. They run on the traditional HPC system and Amazon web services Cloud as well as Linaro Developer Cloud. For the clouds, we have used Intel x86 and ARM processors for running Java codes without changing any line of the program code and without the need for time‐consuming recompilation. Presented applications have been parallelized using the partitioned global address space programming model and its realization in the PCJ library. Our results prove that the PCJ library, due to its performance and ability to create simple portable code, has great promise to be successful for the parallelization of various applications and run them on the cloud with a performance close to HPC systems.
Zn-xZr alloys (x = 0.01, 0.02, 0.05, 0.1 wt%) were designed to improve the poor mechanical properties of pure zinc, a potential biodegradable material for biomedical implants. The microaddition of Zr ...and the application of the indirect hot extrusion process resulted in effective grain refinement of the investigated alloys. Alloys with smaller Zr additions were characterized by finer grains, but brittle fracture mode and minor mechanical properties improvement. The most promising sample was the as-extruded Zn0.05Zr alloy, with a yield strength of 104 MPa, ultimate tensile strength of 157 MPa, elongation to failure of 22%.
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•Zr microaddition leads to creation of intermetallic Zr-rich phase in the Zn matrix.•The hot extrusion process results in visible grain size reduction in the alloys.•The improvement of strength and ductility is observed in the extruded Zn-Zr alloys.
Abnormal grain growth (AGG) in a Zn-0.8Ag (wt%) alloy, produced through the application of high-pressure torsion (HPT), was systematically investigated using scanning electron microscopy (SEM), ...electron backscattered diffraction (EBSD), high-resolution transmission electron microscopy (HR-TEM) and microhardness testing. The HPT-deformed alloy exhibits AGG at room temperature without any additional heat treatment. Analysis by EBSD revealed oriented grain nucleation in a {112¯0}〈0001〉 direction from the initial (0001) fibre texture which agrees with the maximum energy release model. New grains were oriented according to the minimal Young's modulus direction (c-axis), parallel to the shearing direction. The strain-induced dissolution of nanocrystalline Zn3Ag precipitates was identified as the main driving force for AGG in this alloy. The strains necessary for the initiation and termination of AGG were determined as ~4.0 and ~5.0, respectively. The increase in solid-solution strengthening caused an increase in hardness from ~47 HK in the fine-grained centre to ~84 HK in the coarse-grained region. A Hall-Petch investigation revealed grain refinement softening below a grain size of 23 µm. These results provide the first comprehensive description of AGG in metallic materials processed by a severe plastic deformation method at room temperature.
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The effect of Al and Ti additions on the microstructure and properties of CoNiFe alloys was studied in this paper. The investigations were conducted on four specially designed and produced arc ...furnace alloys (from 3 to 5 components, with medium to high entropy). Samples in various states were analyzed, i.e., as-cast, after homogenization, after solution heat treatment, and after solution heat treatment and aging. The obtained samples were characterized by: SEM observations, EDS, XRD, TEM analyses, and finally, hardness measurements. The solid solution strengthening coming from the addition of 5 at. pct. Al was negligible, while the effect from the 5 at. pct. of Ti addition was significant. The precipitation hardening effect related to the presence of the (CoNi)3Ti phase caused by the Ti addition is comparable with the total effect of the Al and Ti addition, which caused the precipitation of (NiCo)3AlTi.
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}112‾0 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.
For the precise determination of orientations in polycrystalline materials, electron backscatter diffraction (EBSD) requires a consistent calibration of the diffraction geometry in the scanning ...electron microscope (SEM). In the present paper, the variation of the projection center for the Kikuchi diffraction patterns which are measured by EBSD is calibrated using a projective transformation model for the SEM beam scan positions on the sample. Based on a full pattern matching approach between simulated and experimental Kikuchi patterns, individual projection center estimates are determined on a subgrid of the EBSD map, from which least-square fits to affine and projective transformations can be obtained. Reference measurements on single-crystalline silicon are used to quantify the orientation errors which result from different calibration models for the variation of the projection center.
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.
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•Multiphase Zn–3Ag-0.5 Mg alloy exhibits high strength and limited plasticity.•Cold rolling (CR) eliminates the brittleness obtained in the hot-extruded state.•Grain refinement and second phases' fraction control the plasticity in the CR state.•Short-time heat treatment restores the strength reduced after CR.•The best obtained mechanical results are UTS of 432 MPa, YS of 322 MPa, EF of 34%.
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