The dynamic recrystallization and carbides precipitation of the Cr-Co-Mo-Ni bearing steel were investigated by hot compression tests performed at temperatures ranging from 850 ℃to 1080 ℃ with strain rate of 1-20 s-1...The dynamic recrystallization and carbides precipitation of the Cr-Co-Mo-Ni bearing steel were investigated by hot compression tests performed at temperatures ranging from 850 ℃to 1080 ℃ with strain rate of 1-20 s-1. The activation energy（Q） for the tested steel is calculated to be around 682.99 k J/mol at a deformation strain of 0.6. Microstructural analysis by SEM shows that the dynamic recrystallization（DRX） behavior is dependent sensitively on the deformation strain, temperature and strain rate, while an exponential relationship between DRX grain size and Z parameter is obtained from the computational formula. Moreover, the M6C-type carbides（〈1 μm） act as the main prohibitor of grain coarsening, and the polynomial regression relationship between them is worked out. With electron backscatter diffraction（EBSD） observation, DRX is the main nucleation mechanism responsible for the formation of new grains during hot compression. In conclusion, the interaction between DRX affected by hot deformation parameters and carbides precipitation determines the ultimate grain size refinement.展开更多
YxVO4∶0.01Dy3+ and Y0.99-xVO4∶0.01Dy3+,xBi3+ phosphors were synthesized by chemical co-precipitation method.Their crystal structure,micromorphology and photoluminescence(PL) properties were investigated by X-ray dif...YxVO4∶0.01Dy3+ and Y0.99-xVO4∶0.01Dy3+,xBi3+ phosphors were synthesized by chemical co-precipitation method.Their crystal structure,micromorphology and photoluminescence(PL) properties were investigated by X-ray diffraction(XRD),scan electron microscopy(SEM) and spectrofluorometer.YxVO4∶0.01Dy3+ and Y0.99-xVO4∶0.01Dy3+,xBi3+ phosphors have a broad excitation band from about 250 to 350 nm including a strongest peak at about 310 nm.Under its excitation,the emission spectra exhibits two sharp peaks,one of which centered at about 483 nm for 4F9/2→6H15/2 transition of Dy3+ and the other at about 574 nm due to the 4F9/2→6H13/2 transition of Dy3+.For YxVO4∶0.01Dy3+(x=0.94,0.97,0.99,1.01,1.03) phosphor,with increasing value of x,the body color of phosphor changes from yellow to white and the strongest peak in the excitation spectra shifts a little to shorter wavelength.It is detrimental to luminous intensity when Y3+ content deviates stoichiometric ratio.For Y0.99-xVO4∶0.01Dy3+,xBi3+(x=0.01,0.05,0.1,0.15,0.2,0.25) phosphor,the samples have extraneous bismuth vanadium oxide phase except for the major tetragonal zircon structure when x≥0.20.With increasing value of x,the band edge in the excitation spectra shifts to longer wavelength,the excitation intensity and luminous intensity increase early and decrease late.When the value of x is 0.01,the intensities increase evidently.In addition,the influence of Y3+ or Bi3+ on the color temperature of emission and micromorphology of YVO4∶Dy3+ is slight.展开更多
基金Project(2012AA03A503) supported by the National High Technology Research and Development Program of China
文摘The dynamic recrystallization and carbides precipitation of the Cr-Co-Mo-Ni bearing steel were investigated by hot compression tests performed at temperatures ranging from 850 ℃to 1080 ℃ with strain rate of 1-20 s-1. The activation energy（Q） for the tested steel is calculated to be around 682.99 k J/mol at a deformation strain of 0.6. Microstructural analysis by SEM shows that the dynamic recrystallization（DRX） behavior is dependent sensitively on the deformation strain, temperature and strain rate, while an exponential relationship between DRX grain size and Z parameter is obtained from the computational formula. Moreover, the M6C-type carbides（〈1 μm） act as the main prohibitor of grain coarsening, and the polynomial regression relationship between them is worked out. With electron backscatter diffraction（EBSD） observation, DRX is the main nucleation mechanism responsible for the formation of new grains during hot compression. In conclusion, the interaction between DRX affected by hot deformation parameters and carbides precipitation determines the ultimate grain size refinement.
基金Supported by Shaanxi provincial project of special foundation of key disciplines(101-00X902)Young People Foundation of Xi’an University of Technology(101-210920)
文摘YxVO4∶0.01Dy3+ and Y0.99-xVO4∶0.01Dy3+,xBi3+ phosphors were synthesized by chemical co-precipitation method.Their crystal structure,micromorphology and photoluminescence(PL) properties were investigated by X-ray diffraction(XRD),scan electron microscopy(SEM) and spectrofluorometer.YxVO4∶0.01Dy3+ and Y0.99-xVO4∶0.01Dy3+,xBi3+ phosphors have a broad excitation band from about 250 to 350 nm including a strongest peak at about 310 nm.Under its excitation,the emission spectra exhibits two sharp peaks,one of which centered at about 483 nm for 4F9/2→6H15/2 transition of Dy3+ and the other at about 574 nm due to the 4F9/2→6H13/2 transition of Dy3+.For YxVO4∶0.01Dy3+(x=0.94,0.97,0.99,1.01,1.03) phosphor,with increasing value of x,the body color of phosphor changes from yellow to white and the strongest peak in the excitation spectra shifts a little to shorter wavelength.It is detrimental to luminous intensity when Y3+ content deviates stoichiometric ratio.For Y0.99-xVO4∶0.01Dy3+,xBi3+(x=0.01,0.05,0.1,0.15,0.2,0.25) phosphor,the samples have extraneous bismuth vanadium oxide phase except for the major tetragonal zircon structure when x≥0.20.With increasing value of x,the band edge in the excitation spectra shifts to longer wavelength,the excitation intensity and luminous intensity increase early and decrease late.When the value of x is 0.01,the intensities increase evidently.In addition,the influence of Y3+ or Bi3+ on the color temperature of emission and micromorphology of YVO4∶Dy3+ is slight.
