The superplastic behavior and associated deformation mechanisms of a fine-grained Mg-10.1 Li-0.8Al-0.6Zn alloy(LAZ1011)with a grain size of 3.2μm,primarily composed of the BCCβphase and a small amount of the HCPαph...The superplastic behavior and associated deformation mechanisms of a fine-grained Mg-10.1 Li-0.8Al-0.6Zn alloy(LAZ1011)with a grain size of 3.2μm,primarily composed of the BCCβphase and a small amount of the HCPαphase,were examined in a temperature range of 473 K to 623 K.The microstructural refinement of this alloy was achieved by employing high-ratio differential speed rolling.The best superplasticity was achieved at 523 K and at strain rates of 10^(-4)-5×10^(-4)s^(-1),where tensile elongations of 550±600%were obtained.During the heating and holding stage of the tensile samples prior to tensile loading,a significant increase in grain size was observed at temperatures above 573 K.Therefore,it was important to consider this effect when analyzing and understanding the superplastic deformation behavior and mechanisms.In the investigated strain rate range,the superplastic flow at low strain rates was governed by lattice diffusion-controlled grain boundary sliding,while at high strain rates,lattice diffusion-controlled dislocation climb creep was the rate-controlling deformation mechanism.It was concluded that solute drag creep is unlikely to occur.During the late stages of deformation at 523 K,it was observed that grain boundary sliding led to the agglomeration of theαphase,resulting in significant strain hardening.Deformation mechanism maps were constructed forβ-Mg-Li alloys in the form of 2D and 3D formats as a function of strain rate,stress,temperature,and grain size,using the constitutive equations for various deformation mechanisms derived based on the data of the current tests.展开更多
Europium(Eu^(3+))doped glasses of chemical compositions(55-x)B2O3:10 SiO2:25 Y2O3:10CaO:xEu_(2)O_(3),where x denotes mol%and ranges 0≤x≤2.5,were synthesized by adopting conventional melt quenching technique,Physical...Europium(Eu^(3+))doped glasses of chemical compositions(55-x)B2O3:10 SiO2:25 Y2O3:10CaO:xEu_(2)O_(3),where x denotes mol%and ranges 0≤x≤2.5,were synthesized by adopting conventional melt quenching technique,Physical properties like density,molar volume,polaron radius,inter-ionic distance and field strength of the glass samples were investigated to assess the impact of Eu_(2)O_(3).Optical and luminescence properties of the glasses were characterized with optical absorption,photoluminescence,X-ray induced emission spectra,temperature dependence emission spectra and decay times.Judd-Ofelt(JO)intensity parameters(Ωλ)of the glasses were evaluated based on the absorption spectrum of 0.5 mol%.JO parameters,calculated from absorption spectra with thermal corrections on oscillator strength,were used to evaluate radiative properties such as radiative transition probability(AR),branching ratio(β_(R)),stimulated cross section emission(σ)and radiative lifetime(τ_(R))for 5D0→7 FJ(J=0,1,2,3 and 4)transitions.The decay rate of^(5)D0 fluorescent level for all the glass samples was single exponential.Lifetimes of the^(5)D0 level were decreased with increasing concentrations of Eu^(3+)ions from 0.05 mol%to 2.5 mol%which might be due to energy transfer through cross-relaxation in the glasses.The chromaticity coordinates(x,y)were similar for all BSYCaEu glasses and were located at the red region of CIE 1931 color chromaticity diagram.Hence,these results confirm that the Eu^(3+)doped BSYCaEu glasses could be useful for visible red lasers and glass scintillation applications.展开更多
文摘The superplastic behavior and associated deformation mechanisms of a fine-grained Mg-10.1 Li-0.8Al-0.6Zn alloy(LAZ1011)with a grain size of 3.2μm,primarily composed of the BCCβphase and a small amount of the HCPαphase,were examined in a temperature range of 473 K to 623 K.The microstructural refinement of this alloy was achieved by employing high-ratio differential speed rolling.The best superplasticity was achieved at 523 K and at strain rates of 10^(-4)-5×10^(-4)s^(-1),where tensile elongations of 550±600%were obtained.During the heating and holding stage of the tensile samples prior to tensile loading,a significant increase in grain size was observed at temperatures above 573 K.Therefore,it was important to consider this effect when analyzing and understanding the superplastic deformation behavior and mechanisms.In the investigated strain rate range,the superplastic flow at low strain rates was governed by lattice diffusion-controlled grain boundary sliding,while at high strain rates,lattice diffusion-controlled dislocation climb creep was the rate-controlling deformation mechanism.It was concluded that solute drag creep is unlikely to occur.During the late stages of deformation at 523 K,it was observed that grain boundary sliding led to the agglomeration of theαphase,resulting in significant strain hardening.Deformation mechanism maps were constructed forβ-Mg-Li alloys in the form of 2D and 3D formats as a function of strain rate,stress,temperature,and grain size,using the constitutive equations for various deformation mechanisms derived based on the data of the current tests.
基金Project supported by the Ministry of Science and Technology(MEST),Korea(2015R1A2A1A13001843)Kyungpook National University Research Fund,2016,National Research Council of Thailand(NRCT)Nakhon Pathom Rajabhat University(NPRU)(GB_60_25)
文摘Europium(Eu^(3+))doped glasses of chemical compositions(55-x)B2O3:10 SiO2:25 Y2O3:10CaO:xEu_(2)O_(3),where x denotes mol%and ranges 0≤x≤2.5,were synthesized by adopting conventional melt quenching technique,Physical properties like density,molar volume,polaron radius,inter-ionic distance and field strength of the glass samples were investigated to assess the impact of Eu_(2)O_(3).Optical and luminescence properties of the glasses were characterized with optical absorption,photoluminescence,X-ray induced emission spectra,temperature dependence emission spectra and decay times.Judd-Ofelt(JO)intensity parameters(Ωλ)of the glasses were evaluated based on the absorption spectrum of 0.5 mol%.JO parameters,calculated from absorption spectra with thermal corrections on oscillator strength,were used to evaluate radiative properties such as radiative transition probability(AR),branching ratio(β_(R)),stimulated cross section emission(σ)and radiative lifetime(τ_(R))for 5D0→7 FJ(J=0,1,2,3 and 4)transitions.The decay rate of^(5)D0 fluorescent level for all the glass samples was single exponential.Lifetimes of the^(5)D0 level were decreased with increasing concentrations of Eu^(3+)ions from 0.05 mol%to 2.5 mol%which might be due to energy transfer through cross-relaxation in the glasses.The chromaticity coordinates(x,y)were similar for all BSYCaEu glasses and were located at the red region of CIE 1931 color chromaticity diagram.Hence,these results confirm that the Eu^(3+)doped BSYCaEu glasses could be useful for visible red lasers and glass scintillation applications.
