CoCrFeNiZr0.3 is a two-phase coexisting (Laves + FCC) high-entropy alloy with high strength, excellent corrosion resistance, and thermal stability. However, the inhomogeneous distribution of the ...eutectic structure among the dendrites has a detrimental effect on the coordinated deformation of the material. The current study shows that the grain size, weave structure, and second phase distribution of high-entropy alloys can be significantly changed by thermal deformation, which affects the mechanical and physical properties, as well as the chemical stability of the alloys. In this study, the thermal deformation behavior of CoCrFeNiZr0.3 biphasic hypoeutectic high-entropy alloy was investigated using a Gleeble-3500 thermal simulation tester under the conditions of deformation temperature of 950–1100 °C and deformation rate of 0.001–1 s−1. The results show that CoCrFeNiZr0.3 high-entropy alloy has higher deformation activation energy, which means its deformation resistance is larger. In addition, the microstructure with finer grain size and uniform distribution of Laves phase can be obtained by EBSD analysis after compression at 1000 °C and 0.01 s−1.
In this study, the Mo0.5NbTiZrTax (x = 0.3, 0.5, 0.7) HEAs obtained by arc melting were controlled by the change of Ta content. The microstructure, the wear properties, and the corrosion resistance ...of the alloys were studied systematically. The results revealed that the alloys have the BCC (major) phase + BCC (minor) phase structure. At the same time, the increase in Ta content promotes the refinement of grains and the formation of sub-grains with gradually random orientation at grain boundaries but suppresses the randomization of crystal orientation. This also enriched the defect structure inside the alloys, further induced the formation of Zr-rich second phase particles, high-density stacking fault structures, and disordered Zr-rich BCC phases. The increase in Ta content significantly improved the wear properties of the alloys, which is mainly ascribed to the presence of the tough BCC phase and the combined effects of solid solution strengthening, second phase strengthening, fine grain strengthening, lattice distortion effect, and stacking fault strengthening. The electrochemical measurements confirm that the overall corrosion resistance of the alloys shows a trend of first increasing and then decreasing with the increase of Ta content due to the formation of micro batteries between the second phase rich in Zr as the anode and dendrites.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
An endfire frequency scanning tapered slot antenna (FSTSA) is proposed and investigated. The proposed FSTSA is a two-conductor structure with a gradient slots array etched only on one of two inner ...edges in the FSTAS. The asymmetrical inner edges enable the antenna to excite two modes with different phase constants simultaneously along the two inner edges. Due to dispersion characteristics of spoof surface plasmon polaritons (SSPPs), the phase difference between the EM waves along the two conductors changes versus frequencies, which enables the main lobe of the FSTSA to scan through the endfire direction. An analysis model is conceived to provide insights into the design, which accurately predicts main lobe directions and initial values of the proposed antenna. The proposed antenna is fabricated, and the measured results show that the main lobe of the antenna scans from −15° to 14° (endfire direction at 0°) from 6.60 to 7.70 GHz, with the scanning rate of 26.4°/GHz. This antenna could be suitable for radar, plane integrated communication system, and certain other beam-scanning applications.
A bidirectional scanning antenna (BSA) based on surface wave mode is proposed. The bidirectional scanning capacity is achieved by two back-to-back placed frequency scanning tapered slot antenna ...(FSTSA) elements. The corrugated slot array in inner edges enables the BSA to support two surface wave modes to propagate along the inner edges with different phase constants. Due to the dispersion characteristic of surface wave mode, the phase difference between two modes varies with frequencies, then frequency scanning is achieved at the endfire. Slot arrays are also etched on the outer edges to reduce current flowing. By separately configuring two back-to-back FSTSA elements, the BSA could form a rotationally symmetrical, mirror symmetrical, or asymmetrical bidirectional scanning pattern. Three prototypes with rotationally symmetrical, mirror symmetrical, and asymmetrical pattern are designed and fabricated to verify the principles. Since the scanning plane is parallel to antenna surface, the proposed BSA has a low cross section, which makes it suitable for wireless communication in tunnels and coal mines where good air ventilation is required.
Laser remelting (LR) treatment was used to regulate the microstructure of AlCoCrFeNiTax high-entropy alloys prepared by vacuum arc melting, and the microstructure and properties of the alloys before ...and after LR treatment were analyzed. The original AlCoCrFeNiTax alloys have typical dendritic morphology and the addition of Ta element promoted the formation of a Laves phase, gradually changing the alloys from two phase (BCC + B2) to three phase (BCC + B2 + Laves phase). After LR treatment, the grains were significantly refined, elemental segregation was alleviated, and a dense remelting layer with a thickness of 1200–1600 µm was formed on the surface of the alloy. In addition, the hardness and wear resistance of the alloys were improved with increasing Ta content and LR treatment, mainly caused by the combined effects of solution strengthening, second phase strengthening and fine grain strengthening. At the same time, the corrosion resistance of the alloys before and after LR treatment in 3.5 wt% NaCl solution is significantly improved by a stable Ta2O5 and TaO2 passivation films and the formation of a dense uniform remelting layer.
•Refractory element was added and LR treatment was conducted on the surface of AlCoCrFeNiTax high entropy alloy.•After LR treatment, elemental segregation on the alloy surface is alleviated and the alloy grains are refined.•A remelted layer of about 1200–1600 µm thickness was formed on the alloy surface after LR treatment.•The hardness and wear resistance of the alloys were improved with increasing Ta content and LR treatment.•The corrosion resistance of the alloys in 3.5 wt% NaCl solution is improved by passivation film and remelted layer.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In order to improve the properties of AlCoCrFeNiNbx (x = 0, 0.1, and 0.5) high-entropy alloys (HEAs), the microstructure of the AlCoCrFeNiNbx is regulated by laser remelting (LR). By testing the ...microstructure and properties of alloys before and after LR treatment，the results indicate that the original AlCoCrFeNiNbx alloys have typical dendritic morphology, and the addition of the Nb element promoted the formation of Laves phase. The grains were significantly refined after LR treatment, and the dense remelting layers with thicknesses ranging from 1200 μm to 1650 μm were formed on the surface of the alloys. In addition, the hardness and wear resistance of the alloys were improved with the increase of Nb content and LR treatment due to the combined effect of fine grain strengthening, solid solution strengthening, and the second phase strengthening. At the same time, the corrosion resistance of the alloys before and after LR treatment in 3.5 wt% NaCl solution was significantly improved by the stable Nb2O5 passivation film for Nb0 and Nb1 alloys.
•LR treatment was conducted on the surface of as-cast AlCoCrFeNiNbx (x = 0.1,0.5 and 1) high entropy alloys.•AlCoCrFeNiNbx alloys have typical dendritic morphology, and the addition of the Nb element promoted the formation of Laves phase.•The grains were significantly refined after LR treatment, and the dense remelting layers with thicknesses ranging from 1200 μm to 1650 μm were formed on the surface of the alloys.•The hardness and wear resistance of the alloys were improved with the increase of Nb content and LR treatment due to the combined effect of fine grain strengthening, solid solution strengthening, and the second phase strengthening.•The corrosion resistance of the alloys before and after LR treatment in 3.5 wt% NaCl solution was significantly improved by the stable Nb2O5 passivation film for Nb0 and Nb1 alloys.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
CoCrFeNiZrsub.0.3 is a two-phase coexisting (Laves + FCC) high-entropy alloy with high strength, excellent corrosion resistance, and thermal stability. However, the inhomogeneous distribution of the ...eutectic structure among the dendrites has a detrimental effect on the coordinated deformation of the material. The current study shows that the grain size, weave structure, and second phase distribution of high-entropy alloys can be significantly changed by thermal deformation, which affects the mechanical and physical properties, as well as the chemical stability of the alloys. In this study, the thermal deformation behavior of CoCrFeNiZrsub.0.3 biphasic hypoeutectic high-entropy alloy was investigated using a Gleeble-3500 thermal simulation tester under the conditions of deformation temperature of 950–1100 °C and deformation rate of 0.001–1 ssup.−1. The results show that CoCrFeNiZrsub.0.3 high-entropy alloy has higher deformation activation energy, which means its deformation resistance is larger. In addition, the microstructure with finer grain size and uniform distribution of Laves phase can be obtained by EBSD analysis after compression at 1000 °C and 0.01 ssup.−1.
In this work, a TiN/TiCN/Alsub.2Osub.3/TiN coating deposited onto cemented carbide matrix by chemical vapor deposition was irradiated by high-current pulsed electron beam (HCPEB). The influence of ...pulse times on the phase composition, microstructure, and mechanical properties of the coating investigated. The results showed that no new phase was produced, the grain size of the coating surface was refined, the surface became flat, and the surface roughness decreased after HCPEB treatment. The TiN/TiCN/Alsub.2Osub.3/TiN coating presented a smooth surface with good mechanical performance after HCPEB. A maximum hardness was obtained after 15 pulses, and the 15-pulse irradiated coating showed better wear resistance. The improvement in the coating’s performance after irradiation was mainly attributed to the formation of grain refinement and crystal defects, as well as the change of stress field inside the coating. The objective of this study was to evaluate the potential of HCPEB modification in the preparation of high-performance coating by analyzing the microstructure and property of coating under different pulses.
In this work, a TiN/TiCN/Al2O3/TiN coating deposited onto cemented carbide matrix by chemical vapor deposition was irradiated by high-current pulsed electron beam (HCPEB). The influence of pulse ...times on the phase composition, microstructure, and mechanical properties of the coating investigated. The results showed that no new phase was produced, the grain size of the coating surface was refined, the surface became flat, and the surface roughness decreased after HCPEB treatment. The TiN/TiCN/Al2O3/TiN coating presented a smooth surface with good mechanical performance after HCPEB. A maximum hardness was obtained after 15 pulses, and the 15-pulse irradiated coating showed better wear resistance. The improvement in the coating’s performance after irradiation was mainly attributed to the formation of grain refinement and crystal defects, as well as the change of stress field inside the coating. The objective of this study was to evaluate the potential of HCPEB modification in the preparation of high-performance coating by analyzing the microstructure and property of coating under different pulses.
A technology based on theory of small reflections for open stopband suppression in the periodic leaky-wave antennas (PLWA) is presented. The open stopband suppression is realized by the superposition ...and cancellation of multiple reflected waves generated by discontinuities of periodic structures. By modifying the discontinuities, the phase and amplitude of each reflected wave could be modulated separately within a certain frequency band. Choosing the proper phase and amplitude of reflected waves, the total reflected wave could be reduced to a low level, even to zero, and then, the abnormally large reflection in the open stopband is suppressed. Two spoof surface plasmon polaritons (SSPP) based PLWA are developed to verify the technology. The results show that good VSWRs and radiation performances are achieved when the beam scans through broadside direction. This technology could have applications in the design of various types of PLWA, such as microstrip, waveguide, and SSPP PLWAs.
