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.
In this study, a new biodegradable alloy from the Zn-Ag-Zr system was investigated. Most importantly, mechanical properties and ductility were significantly improved in designed Zn1Ag0.05Zr alloy in ...comparison to binary Zn1Ag and previously investigated Zn0.05Zr alloys (wt%). The characterized alloy reached values of yield strength, ultimate tensile strength and elongation to failure equal to 166 ± 2 MPa, 211 ± 1 MPa and 35 ± 1%, respectively. Simultaneous addition of both alloying elements contributed to solid solution strengthening, intermetallic Zr-rich phase formation, and effective grain refinement. Immersion and electrochemical in vitro corrosion tests showed a slight increase of degradation rate in ternary alloy up to 17.1 ± 1.0 μm/year and no significant loss of mechanical properties after 28-day of immersion in simulated physiological solution. In addition, the preliminary antimicrobial studies show antimicrobial activity of the investigated Zn-Ag-Zr alloy against Escherichia coli and Staphylococcus aureus. The presented results demonstrate that newly developed Zn-based alloy can be considered as a promising biodegradable material for medical applications.
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•Simultaneous additions of Ag and Zr result in solid solution strengthening and grain refinement by the presence of intermetallic Zn22Zr phase;•Hot extruded Zn1Ag0.05Zr alloy shows enhanced strength and improved ductility in comparison to binary alloys;•The designed Zn1Ag0.05Zr alloy exhibits biodegradation in Hanks' solution with corrosion rate 17.1 ± 1.0 μm/year;•Investigated alloys from Zn-Ag-Zr system possess the ability to inhibit bacterial growth.
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•Additions of Ag and Mg provided grain refinement and multiphase microstructure.•Investigated Zn alloys degraded mainly via intergranular and micro galvanic corrosion.•Refined Zn ...grains and evenly distributed small precipitates provided uniform corrosion.•Precipitates of the ε-Zn3Ag phase corroded slower than Zn and remained in the pits.•The corrosion rate of the Zn-3Ag-0.5Mg alloy after 180-day immersion was 21.6 µm/year.
In this paper, Zn-3Ag and Zn-3Ag-0.5Mg alloys were studied in terms of applicability as biodegradable implant materials. The performed tensile, compression and bending tests indicate a high strengthening effect induced by the Ag and Mg additions, additionally resulting in grain size refinement. It was shown that sustaining plastic strain during deformation depends on the applied stress causing asymmetric mechanical behavior of the tested Zn-based materials. Electrochemical measurements and immersion tests in Hanks' solution lasting up to 180 days revealed that Ag and Mg contribute to the change of the Zn matrix's open circuit potential and the formation of micro-galvanic cells between the Zn grains and precipitates. The fine-grained microstructure and evenly distributed small precipitates led to uniform corrosion occurring via pit formation on the corroded surface due to intergranular and micro-galvanic corrosion mechanisms. The corrosion rate of the Zn-3Ag-0.5Mg alloy after 180 days was almost twice that of pure Zn and the Zn-3Ag alloy.
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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•Optimization of doping strategy for high-performance eco-friendly Li-ion cathodes.•Electrochemical impedance spectroscopy studies of doped lithium-manganese spinels.•GITT measurements for ...high-performance materials using various current pulses.•Understanding the influence of K and S doping on materials’ electronic conductivity.
K and S doped LiMn2O4 (general composition: Li1-xKxMn2O4-ySy, x=0.01, 0.02; y=0.01, 0.02, 0.03) is a high-performance cathode material for lithium-ion batteries. Its synthesis through sol-gel route is facile, efficient and eco-friendly, while giving a uniform nanocrystalline material with strictly controllable composition. In the present work, LKMOS has been synthesized with four different combinations of potassium and sulfur dopants, giving materials with compositions of Li0.99K0.01Mn2O3.99S0.01, Li0.99K0.01Mn2O3.98S0.02, Li0.99K0.01Mn2O3.97S0.03 and Li0.98K0.02Mn2O3.99S0.01. Obtained materials has been tested in Li-ion half cells in order to determine the effect of different dopant combinations on cathode's Li+ transport kinetics, impedance and high-power performance. Materials are characterized by X-ray diffraction and X-ray fluorescence. The electrochemical performance of the materials is examined by a galvanostatic charge-discharge tests, galvanostatic intermittent titration technique and electrochemical impedance spectroscopy. Electrochemical impedance tests have shown the effect of dopant amount in both oxygen and lithium sublattice on the half-cell internal resistances. The optimal composition of K and S doped LMO cathode for high-power application has been established.
A novel Zn-3Ag-0.5Mg alloy was plastically deformed using 3 processing paths: hot extrusion (HE), HE followed by cold rolling (CR) and high-pressure torsion (HPT). The processed samples consisted of ...the
η
-Zn phase,
ε
-Zn
3
Ag precipitates within the matrix, and nanometric Zn
2
Mg precipitates within the Zn
11
Mg
2
phase located at the grain boundaries. Both the
η
-Zn phase and Mg-rich phases were enriched in Ag. Electron backscattered diffraction was used to examine the effects of grain size and texture on mechanical behavior with tensile tests performed at room temperature (RT) at different strain rates. The coarse-grained (~ 6
µ
m) samples after HE exhibited high strength with brittleness due to dislocation interaction with dispersed precipitates and, to some extent, with twinning activation. Significant grain refinement and processing at RT gave an increase in elongation to over 50 pct in CR and 120 pct in HPT. Ductile CR samples with an average grain size of ~ 2
µ
m and favorable rolling deformation texture gave a yield strength of ~ 254 MPa, a tensile strength of ~ 456 MPa, and a reasonable strain rate sensitivity. These values for the CR samples meet the mechanical requirements for biodegradable stents in cardiovascular applications.
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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