The dissimilar joints of AZ61 and ZK60 magnesium alloys were obtained by tungsten inert gas arc(TIG)welding and activating tungsten inert gas arc(A-TIG)welding processes.Microstructure characterization shows that,the ...The dissimilar joints of AZ61 and ZK60 magnesium alloys were obtained by tungsten inert gas arc(TIG)welding and activating tungsten inert gas arc(A-TIG)welding processes.Microstructure characterization shows that,the fineα-Mg equiaxed dendrite crystals contained Mg17Al12 and MgZn2 particles in the fusion zone.The average size of theα-Mg grains in the fusion zone was refined to 19μm at welding current of 80 A,which resulted in the largest tensile strength of 207 MPa.The tensile strength and the width of the beam of the A-TIG welded AZ61/ZK60 joints showed strong dependence on the amount of TiO2.However,the inhomogeneity of the heat-affected zone near different base metals presented no significant effect on the mechanical properties of the welded joint.展开更多
The effects of graphene nanoplates(GNPs)on the microstructures and mechanical properties of nanoparticlesstrengthening activating tungsten inert gas arc welding(NSA-TIG)welded AZ31magnesium alloy joints were investiga...The effects of graphene nanoplates(GNPs)on the microstructures and mechanical properties of nanoparticlesstrengthening activating tungsten inert gas arc welding(NSA-TIG)welded AZ31magnesium alloy joints were investigated.It wasfound that compared with those of activating TIG(A-TIG),and obvious refinement ofα-Mg grains was achieved and the finestα-Mggrains of fusion zone of NSA-TIG joints were obtained in the welded joints with TiO2+GNPs flux coating.In addition,thepenetrations of joints coated by TiO2+GNPs flux were similar to those coated by the TiO2+SiCp flux.However,the welded jointswith TiO2+GNPs flux coating showed better mechanical properties(i.e.,ultimate tensile strength and microhardness)than those withTiO2+SiCp flux coating.Moreover,the generation of necking only occurred in the welded joints with TiO2+GNPs flux.展开更多
A novel approach to widening the active reflection coefficient(ARC)bandwidth of an antenna array,employing a parasitic coupling network(PCN),is investigated in this article.Different from traditional tightly coupled a...A novel approach to widening the active reflection coefficient(ARC)bandwidth of an antenna array,employing a parasitic coupling network(PCN),is investigated in this article.Different from traditional tightly coupled arrays adopting space structures for enhancing the coupling in balanced-excitation antennas,a PCN derived from rigorous formulas is employed in the feeding lines of unbalanced-excitation ones.Based on network analysis,the mutual coupling utilization condition for an(M×N)-element antenna array is initially deduced,and the PCN is implemented.Then,the PCNs are realized by introducing a parasitic element and a coupling network between the two-element H-plane and E-plane dual-layer coupled microstrip antenna arrays,resulting in 10.9%and 30.8%bandwidth enhancements compared with the original arrays,respectively.Moreover,the PCNs are further expanded to multielement antenna arrays,including three-and five-element one-dimensional and 8×2 twodimensional arrays,exhibiting approximately 40%overlapped ARC bandwidths with normal radiation patterns,steady gains,and applicable scanning characteristics.The results indicate its potential application in large-scale wideband arrays.展开更多
基金Project(51771160)supported by the National Natural Science Foundation of ChinaProject(2018JJ4048)supported by the Provincial and Municipal Joint Fund for Natural Science of Hunan Province,China
文摘The dissimilar joints of AZ61 and ZK60 magnesium alloys were obtained by tungsten inert gas arc(TIG)welding and activating tungsten inert gas arc(A-TIG)welding processes.Microstructure characterization shows that,the fineα-Mg equiaxed dendrite crystals contained Mg17Al12 and MgZn2 particles in the fusion zone.The average size of theα-Mg grains in the fusion zone was refined to 19μm at welding current of 80 A,which resulted in the largest tensile strength of 207 MPa.The tensile strength and the width of the beam of the A-TIG welded AZ61/ZK60 joints showed strong dependence on the amount of TiO2.However,the inhomogeneity of the heat-affected zone near different base metals presented no significant effect on the mechanical properties of the welded joint.
基金Project(51375511) supported by the National Natural Science Foundation of ChinaProject(cstc2016jcyj A0167) supported by the Research Program of Basic Research and Frontier Technology of Chongqing of China+1 种基金Project(SF201602) supported by the Science and Technology Project in the Field of Social Development of Shapingba District of Chongqing of ChinaProject(XJ201608) supported by the Key Industry Technology Innovation Funds of Science and Technology Development Board of Xiangcheng District of Suzhou of China
文摘The effects of graphene nanoplates(GNPs)on the microstructures and mechanical properties of nanoparticlesstrengthening activating tungsten inert gas arc welding(NSA-TIG)welded AZ31magnesium alloy joints were investigated.It wasfound that compared with those of activating TIG(A-TIG),and obvious refinement ofα-Mg grains was achieved and the finestα-Mggrains of fusion zone of NSA-TIG joints were obtained in the welded joints with TiO2+GNPs flux coating.In addition,thepenetrations of joints coated by TiO2+GNPs flux were similar to those coated by the TiO2+SiCp flux.However,the welded jointswith TiO2+GNPs flux coating showed better mechanical properties(i.e.,ultimate tensile strength and microhardness)than those withTiO2+SiCp flux coating.Moreover,the generation of necking only occurred in the welded joints with TiO2+GNPs flux.
基金supported by the National Natural Science Foundation of China(Nos.62201579 and 62201580)the Youth Independent Innovation Science Foundation of National University of Defense Technology(No.ZK24-39)。
文摘A novel approach to widening the active reflection coefficient(ARC)bandwidth of an antenna array,employing a parasitic coupling network(PCN),is investigated in this article.Different from traditional tightly coupled arrays adopting space structures for enhancing the coupling in balanced-excitation antennas,a PCN derived from rigorous formulas is employed in the feeding lines of unbalanced-excitation ones.Based on network analysis,the mutual coupling utilization condition for an(M×N)-element antenna array is initially deduced,and the PCN is implemented.Then,the PCNs are realized by introducing a parasitic element and a coupling network between the two-element H-plane and E-plane dual-layer coupled microstrip antenna arrays,resulting in 10.9%and 30.8%bandwidth enhancements compared with the original arrays,respectively.Moreover,the PCNs are further expanded to multielement antenna arrays,including three-and five-element one-dimensional and 8×2 twodimensional arrays,exhibiting approximately 40%overlapped ARC bandwidths with normal radiation patterns,steady gains,and applicable scanning characteristics.The results indicate its potential application in large-scale wideband arrays.
