The 7xxx series alloys are heat treatable wrought aluminium alloys based on the Al-Zn-Mg（-Cu） system. They are widely used in high-performance structural aerospace and transportation applications. Apart from composi...The 7xxx series alloys are heat treatable wrought aluminium alloys based on the Al-Zn-Mg（-Cu） system. They are widely used in high-performance structural aerospace and transportation applications. Apart from compositional, casting and thermo-mechanical processing effects, the balance of properties is also significantly influenced by the way in which the materials are heat-treated. This paper describes the effects of homogenisation, solution treatment, quenching and ageing treatments on the evolution of the microstructure and properties of some important medium to high-strength 7xxx alloys. With a focus on recent work at Monash University, where the whole processing route from homogenisation to final ageing has been studied for thick plate products, it is reported how microstructural features such as dispersoids, coarse constituent particles, fine-scale precipitates, grain structure and grain boundary characteristics can be controlled by heat treatment to achieve improved microstructure-property combinations. In particular, the paper presents methods for dissolving unwanted coarse constituent particles by controlled high- temperature treatments, quench sensitivity evaluations based on a systematic study of continuous cooling precipitation behaviour, and ageing investigations of one-, two- and three-step ageing treatments using experimental and modelling approaches, in each case, the effects on both the microstructure and the resulting properties are discussed.展开更多
In this study Cu<sup>2+</sup>+Eu<sup>3+</sup> co-doped ZnO(ZnO/Cu<sup>2+</sup>+Eu<sup>3+</sup>) solid solution powders were synthesized by solution combustion method usi...In this study Cu<sup>2+</sup>+Eu<sup>3+</sup> co-doped ZnO(ZnO/Cu<sup>2+</sup>+Eu<sup>3+</sup>) solid solution powders were synthesized by solution combustion method using as oxidant agent zinc nitrate hexahydrate and as fuel urea;the Cu<sup>2+</sup> concentrations were 0, 1, 2, 3, 10, and 20 %Wt;the Eu<sup>3+</sup> ion concentration was fixed in 3%Wt. The samples after were annealed at 900°C by 20 h in air. The structural results showed the largely presence of a wurtzite solid solution of Cu<sup>2+</sup>+Eu<sup>3+</sup>doped ZnO, at high Cu<sup>2+</sup> doping CuO and Eu<sub>2</sub>CuO<sub>4</sub> phases are also present. Morphological properties were analyzed using scanning electron microscopy (SEM) technique. However it is important to remark that the Cu<sup>2+</sup> ions suppress the Eu<sup>3+</sup> ion photoluminescence (PL) by means of an overlap mechanism between Cu<sup>2+</sup> absorption band and Eu<sup>3+</sup>emission band (e.g. <sup>5</sup>D<sub>0</sub>→<sup>7</sup>F<sub>2</sub>) of the Eu<sup>3+</sup> emission spectra.展开更多
Sr3-z（AlxSi1-x）O5-xFx：zCe^3＋ phosphors were synthesized by high-temperature solid-state reaction. The structure and lumi- nescence properties of phosphors with various A1/Si ratios and Ce3＋ concentrations were ch...Sr3-z（AlxSi1-x）O5-xFx：zCe^3＋ phosphors were synthesized by high-temperature solid-state reaction. The structure and lumi- nescence properties of phosphors with various A1/Si ratios and Ce3＋ concentrations were characterized using various methods such as X-ray diffraction, photoluminescence excitation and photoluminescence spectra. XRD result displayed that a complete solid solution between Sr3AlO4F and Sr3SiO5 was formed. With the increasing ofx value, a broader excitation band and stronger absorption appeared in the blue light region. Moreover, the emission band shifted to a shorter wavelength and the emission intensity reached a maximum at x=0.6. By adjusting the concentration of Ce3＋, a widely tunable range of emission wavelength under the excitation of 460 um was obtained from the green to yellow regions. In addition, the concentration and thermal quenching were also discussed.展开更多
This paper discusses the global existence and quenching of the solution to the Newton filtration equation with the nonlinear boundary condition. The authors also discuss the profile of the quenching solution in the qu...This paper discusses the global existence and quenching of the solution to the Newton filtration equation with the nonlinear boundary condition. The authors also discuss the profile of the quenching solution in the quenching time and obtain the quenching rate of the quenching solution.展开更多
In this paper,we study a simplified Othmer-Stevens model with reproduction term. By making use of a smart function transformation,the comparative method and some special mathe-matical analysis,we prove the existence o...In this paper,we study a simplified Othmer-Stevens model with reproduction term. By making use of a smart function transformation,the comparative method and some special mathe-matical analysis,we prove the existence of global,blow-up or quenching solutions of the problem on different conditions. More interesting results are reached. The result of the paper not only verifies a real biological phenomenon,but also provides a theo-retical groundwork for numerical problems of the chemotaxis model.展开更多
Let Ω be a bounded or unbounded domain in R~n. The initial-boundary value problem for the porous medium and plasma equation with singular terms is considered in this paper. Criteria for the appearance of quenching ph...Let Ω be a bounded or unbounded domain in R~n. The initial-boundary value problem for the porous medium and plasma equation with singular terms is considered in this paper. Criteria for the appearance of quenching phenomenon and the existence of global classical solution to the above problem are established. Also, the life span of the quenching solution is estimated or evaluated for some domains.展开更多
The effect of the quenching rate after solution treatment on the residual stress and precipitation behavior of a high strength Mg-5 Zn-3.5 Sn-1 Mn-0.5 Ca-0.5 Cu plate is studied.The simulation results show decreasing ...The effect of the quenching rate after solution treatment on the residual stress and precipitation behavior of a high strength Mg-5 Zn-3.5 Sn-1 Mn-0.5 Ca-0.5 Cu plate is studied.The simulation results show decreasing temperature gradient in the plate with decreasing quenching rate,which leads to weakened inhomogeneous plastic deformation and decreased residual stress.No dynamic precipitation on the grain boundary happens after either cold water cooling or air cooling,however,air cooling leads to dynamic precipitation of Mg-Zn phase on Mn particles around which a low-density precipitate zone develops after aging treatment.Moreover,the fine and densely distributed Mg-Zn precipitates observed after aging treatment of the cold water cooled alloy are replaced by coarse precipitates with low density for the air cooled alloy.Both the low-density precipitate zone near Mn particles and the coarsening of precipitates are the source of the decrease in hardness and tensile properties of the air cooled alloy.The residual stress drops faster than the hardness with decreasing quenching rate,which makes it possible to lower the residual stress without sacrificing too much age-hardening ability of the alloy.展开更多
基金The Aluminium Corporation of China Ltd.(Chalco)for supporting aspects of this work financiallyproviding AA7150 materials as part of the Australia-China International Centre for Light Alloy Research(ICLAR)+1 种基金Monash University for developing the retrogression and reageing Matlab model (as part of the PhD project of Dr Adrian GROSVENOR)The ARC Centre of Excellence for Design in Light Metals and its Directors (first Prof Barry MUDDLE and then Prof Xin-hua WU) for supporting
文摘The 7xxx series alloys are heat treatable wrought aluminium alloys based on the Al-Zn-Mg（-Cu） system. They are widely used in high-performance structural aerospace and transportation applications. Apart from compositional, casting and thermo-mechanical processing effects, the balance of properties is also significantly influenced by the way in which the materials are heat-treated. This paper describes the effects of homogenisation, solution treatment, quenching and ageing treatments on the evolution of the microstructure and properties of some important medium to high-strength 7xxx alloys. With a focus on recent work at Monash University, where the whole processing route from homogenisation to final ageing has been studied for thick plate products, it is reported how microstructural features such as dispersoids, coarse constituent particles, fine-scale precipitates, grain structure and grain boundary characteristics can be controlled by heat treatment to achieve improved microstructure-property combinations. In particular, the paper presents methods for dissolving unwanted coarse constituent particles by controlled high- temperature treatments, quench sensitivity evaluations based on a systematic study of continuous cooling precipitation behaviour, and ageing investigations of one-, two- and three-step ageing treatments using experimental and modelling approaches, in each case, the effects on both the microstructure and the resulting properties are discussed.
文摘In this study Cu<sup>2+</sup>+Eu<sup>3+</sup> co-doped ZnO(ZnO/Cu<sup>2+</sup>+Eu<sup>3+</sup>) solid solution powders were synthesized by solution combustion method using as oxidant agent zinc nitrate hexahydrate and as fuel urea;the Cu<sup>2+</sup> concentrations were 0, 1, 2, 3, 10, and 20 %Wt;the Eu<sup>3+</sup> ion concentration was fixed in 3%Wt. The samples after were annealed at 900°C by 20 h in air. The structural results showed the largely presence of a wurtzite solid solution of Cu<sup>2+</sup>+Eu<sup>3+</sup>doped ZnO, at high Cu<sup>2+</sup> doping CuO and Eu<sub>2</sub>CuO<sub>4</sub> phases are also present. Morphological properties were analyzed using scanning electron microscopy (SEM) technique. However it is important to remark that the Cu<sup>2+</sup> ions suppress the Eu<sup>3+</sup> ion photoluminescence (PL) by means of an overlap mechanism between Cu<sup>2+</sup> absorption band and Eu<sup>3+</sup>emission band (e.g. <sup>5</sup>D<sub>0</sub>→<sup>7</sup>F<sub>2</sub>) of the Eu<sup>3+</sup> emission spectra.
基金Project supported by National Natural Science Foundation of China(50902011)the National Hi-Tech R&D Program of China(863 Program,2011AA03A101)
文摘Sr3-z（AlxSi1-x）O5-xFx：zCe^3＋ phosphors were synthesized by high-temperature solid-state reaction. The structure and lumi- nescence properties of phosphors with various A1/Si ratios and Ce3＋ concentrations were characterized using various methods such as X-ray diffraction, photoluminescence excitation and photoluminescence spectra. XRD result displayed that a complete solid solution between Sr3AlO4F and Sr3SiO5 was formed. With the increasing ofx value, a broader excitation band and stronger absorption appeared in the blue light region. Moreover, the emission band shifted to a shorter wavelength and the emission intensity reached a maximum at x=0.6. By adjusting the concentration of Ce3＋, a widely tunable range of emission wavelength under the excitation of 460 um was obtained from the green to yellow regions. In addition, the concentration and thermal quenching were also discussed.
文摘This paper discusses the global existence and quenching of the solution to the Newton filtration equation with the nonlinear boundary condition. The authors also discuss the profile of the quenching solution in the quenching time and obtain the quenching rate of the quenching solution.
基金Supported by the National Natural Science Foundation of China(10471108)
文摘In this paper,we study a simplified Othmer-Stevens model with reproduction term. By making use of a smart function transformation,the comparative method and some special mathe-matical analysis,we prove the existence of global,blow-up or quenching solutions of the problem on different conditions. More interesting results are reached. The result of the paper not only verifies a real biological phenomenon,but also provides a theo-retical groundwork for numerical problems of the chemotaxis model.
文摘Let Ω be a bounded or unbounded domain in R~n. The initial-boundary value problem for the porous medium and plasma equation with singular terms is considered in this paper. Criteria for the appearance of quenching phenomenon and the existence of global classical solution to the above problem are established. Also, the life span of the quenching solution is estimated or evaluated for some domains.
基金supported by the National Key Research and Development Program of China[2016YFB0301105]the National Key Research and Development Plan[2017YFB0103904]
文摘The effect of the quenching rate after solution treatment on the residual stress and precipitation behavior of a high strength Mg-5 Zn-3.5 Sn-1 Mn-0.5 Ca-0.5 Cu plate is studied.The simulation results show decreasing temperature gradient in the plate with decreasing quenching rate,which leads to weakened inhomogeneous plastic deformation and decreased residual stress.No dynamic precipitation on the grain boundary happens after either cold water cooling or air cooling,however,air cooling leads to dynamic precipitation of Mg-Zn phase on Mn particles around which a low-density precipitate zone develops after aging treatment.Moreover,the fine and densely distributed Mg-Zn precipitates observed after aging treatment of the cold water cooled alloy are replaced by coarse precipitates with low density for the air cooled alloy.Both the low-density precipitate zone near Mn particles and the coarsening of precipitates are the source of the decrease in hardness and tensile properties of the air cooled alloy.The residual stress drops faster than the hardness with decreasing quenching rate,which makes it possible to lower the residual stress without sacrificing too much age-hardening ability of the alloy.
