Based on the experiments, a new technique of reducing tube with two linked 3-roll roller dies was developed. The external friction conditions, velocity and the non-uniform deformation of metal were distinctly improved...Based on the experiments, a new technique of reducing tube with two linked 3-roll roller dies was developed. The external friction conditions, velocity and the non-uniform deformation of metal were distinctly improved, and the friction between metal and tool was decreased. Corrosion strip layers and photo-elastic coatings methods were adopted in the experiment for measuring residual stress, and the residual stresses in the drawn tube with 3-roll dies are reduced.展开更多
Iron-based superconductor,a promising candidate for high-field applications,has attracted significant attentions.For practical utilization,the superconducting tapes should have high transport critical current density(...Iron-based superconductor,a promising candidate for high-field applications,has attracted significant attentions.For practical utilization,the superconducting tapes should have high transport critical current density(J_(c)),low production cost,larger mechanical strength and good homogeneity.In this study,seven-filament Cu/Agsheathed(Ba,K)Fe_(2)As_(2)tapes were fabricated from round and square wires.It is found that the tapes rolled from square wires have a desirable uniformity of filament deformation and distribution,compared with the ones rolled from round wires.Moreover,the J_c of tape was obviously improved by using square drawing dies instead of traditional round ones.For the tapes rolled from square wires annealed under ambient and 2 MPa by hot pressing,the transport J_c values reached 1.51×10^(4) A·cm^(-2)and 4.86×10^(4) A.cm^(-2)(4.2K,10T),respectively.The deformation process on the cross section of the tapes during rolling was analyzed by using the powder-flow model.These results indicate a potential application of Cu/Ag(Ba,K)Fe_(2)As_(2)tapes in high-magnetic-field region.展开更多
Wear resistance of several zirconia toughened ceramics in comparison with a metal-ceramic Co-WC has been studied in drawing wire field test. Result indicates that the harder the ceramic die, the longer the service lif...Wear resistance of several zirconia toughened ceramics in comparison with a metal-ceramic Co-WC has been studied in drawing wire field test. Result indicates that the harder the ceramic die, the longer the service life. Excellent wear resistance of ceramic die is obtained with a very high hardness (19 GPa). The service life is nearly three times that of Co-WC die. SEM observation on wear surfaces showed that material removal is mainly caused by plastic flow and ploughing process. But when the ceramic is composed of zirconia, alumina and some titanium carbide, micro-chipping and tribochemical reaction take place, and wear rate increases. Wear and friction induced martensite was detected by XRD. The T-M (tetragonal to monoclinic) phase transformation has a contribution to inhibiting microfracture.展开更多
文摘Based on the experiments, a new technique of reducing tube with two linked 3-roll roller dies was developed. The external friction conditions, velocity and the non-uniform deformation of metal were distinctly improved, and the friction between metal and tool was decreased. Corrosion strip layers and photo-elastic coatings methods were adopted in the experiment for measuring residual stress, and the residual stresses in the drawn tube with 3-roll dies are reduced.
基金financially supported by the National Natural Science Foundation of China(Nos.U1832213,51721005 and 51861135311)the National Key R&D Program of China(Nos.2018YFA0704200 and 2017YFE0129500)+1 种基金the Key Research Program of Frontier Sciences,Chinese Academy of Sciences(No.QYZDJ-SSW-JSC026)the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB25000000)。
文摘Iron-based superconductor,a promising candidate for high-field applications,has attracted significant attentions.For practical utilization,the superconducting tapes should have high transport critical current density(J_(c)),low production cost,larger mechanical strength and good homogeneity.In this study,seven-filament Cu/Agsheathed(Ba,K)Fe_(2)As_(2)tapes were fabricated from round and square wires.It is found that the tapes rolled from square wires have a desirable uniformity of filament deformation and distribution,compared with the ones rolled from round wires.Moreover,the J_c of tape was obviously improved by using square drawing dies instead of traditional round ones.For the tapes rolled from square wires annealed under ambient and 2 MPa by hot pressing,the transport J_c values reached 1.51×10^(4) A·cm^(-2)and 4.86×10^(4) A.cm^(-2)(4.2K,10T),respectively.The deformation process on the cross section of the tapes during rolling was analyzed by using the powder-flow model.These results indicate a potential application of Cu/Ag(Ba,K)Fe_(2)As_(2)tapes in high-magnetic-field region.
文摘Wear resistance of several zirconia toughened ceramics in comparison with a metal-ceramic Co-WC has been studied in drawing wire field test. Result indicates that the harder the ceramic die, the longer the service life. Excellent wear resistance of ceramic die is obtained with a very high hardness (19 GPa). The service life is nearly three times that of Co-WC die. SEM observation on wear surfaces showed that material removal is mainly caused by plastic flow and ploughing process. But when the ceramic is composed of zirconia, alumina and some titanium carbide, micro-chipping and tribochemical reaction take place, and wear rate increases. Wear and friction induced martensite was detected by XRD. The T-M (tetragonal to monoclinic) phase transformation has a contribution to inhibiting microfracture.
