The microstructure evolutions of two A1-Zn-Mg alloys, one of which was alloyed with Sc and Zr, and the kinetics of A13（SCl-xZrx） precipitates in the A1-Zn-Mg alloy during homogenization were investigated. Both alloy...The microstructure evolutions of two A1-Zn-Mg alloys, one of which was alloyed with Sc and Zr, and the kinetics of A13（SCl-xZrx） precipitates in the A1-Zn-Mg alloy during homogenization were investigated. Both alloys under as-cast condition with supersaturated, non-equilibrium T（Mg32（A1, Zn）49） phase and impurities phase were displayed. When the homogenization temperatures are below 350 ~C, Zn and Mg atoms precipitate from matrix; however, when the temperatures are above 400 ~C, T phase dissolves into matrix, enhancing solid-solution strengthening. Kinetics of A13（Scl.xZrx） precipitates was studied based on Jmat Pro software calculation and the difference values between the hardness of the two alloys in each homogenization condition. The calculations predict that the Sc and Zr solubilities in ct-A1 decline with the presence of Mg and Zn. Investigation of the difference values reveals that when the temperature is between 300 ~C and 350 ~C, the nucleation rate of A13（Sc1-xZrx） precipitates is the highest and the strengthening effect from A13（SCl_xZrx） precipitates is the best. After homogenization at 470℃ for 12 h, non-equilibrium T phase disappears, while impurity phase remains. The mean diameter of A13（Scl_xZrx） precipitates is around 18 urn. Ideas about better fulfilling the potentials of Sc and Zr were proposed at last.展开更多
Extending Long＇s （2001） two-sector model into a three-sector model, this paper constructs a new framework for analysing the evolution mechanism of the structure of technology exports. The authors also have applied ...Extending Long＇s （2001） two-sector model into a three-sector model, this paper constructs a new framework for analysing the evolution mechanism of the structure of technology exports. The authors also have applied an adjusted Hausman model to measure the structure of exported technology at China＇s provincial level regions. Upon this foundation, approaching the subject from its domestic and international impact factors, this paper empirically tests the motives driving the structural transformation of China＇s technology export. The conclusions are： （1） the structure of China＇s technology export has improved significantly in recent years, but not as highly as measured by Rodrik （2006） et al. （2） The dynamic mechanism of the structure of China＇s technology export differs from that of the other developing countries. At national and regional levels, the mounting physical capital stock is the fundamental driving force, but with obvious decreasing marginal utility. （3） Excessive unskilled labor in the capital production sector in the central and western regions, and excessively low export prices in the eastern regions have caused negative effects of the skilled labor in the western region and unskilled labor in the eastern region on local structure of technology export.展开更多
基金Project(JPPT-115-2-948) supported by the National Civilian Matched Project of China
文摘The microstructure evolutions of two A1-Zn-Mg alloys, one of which was alloyed with Sc and Zr, and the kinetics of A13（SCl-xZrx） precipitates in the A1-Zn-Mg alloy during homogenization were investigated. Both alloys under as-cast condition with supersaturated, non-equilibrium T（Mg32（A1, Zn）49） phase and impurities phase were displayed. When the homogenization temperatures are below 350 ~C, Zn and Mg atoms precipitate from matrix; however, when the temperatures are above 400 ~C, T phase dissolves into matrix, enhancing solid-solution strengthening. Kinetics of A13（Scl.xZrx） precipitates was studied based on Jmat Pro software calculation and the difference values between the hardness of the two alloys in each homogenization condition. The calculations predict that the Sc and Zr solubilities in ct-A1 decline with the presence of Mg and Zn. Investigation of the difference values reveals that when the temperature is between 300 ~C and 350 ~C, the nucleation rate of A13（Sc1-xZrx） precipitates is the highest and the strengthening effect from A13（SCl_xZrx） precipitates is the best. After homogenization at 470℃ for 12 h, non-equilibrium T phase disappears, while impurity phase remains. The mean diameter of A13（Scl_xZrx） precipitates is around 18 urn. Ideas about better fulfilling the potentials of Sc and Zr were proposed at last.
文摘Extending Long＇s （2001） two-sector model into a three-sector model, this paper constructs a new framework for analysing the evolution mechanism of the structure of technology exports. The authors also have applied an adjusted Hausman model to measure the structure of exported technology at China＇s provincial level regions. Upon this foundation, approaching the subject from its domestic and international impact factors, this paper empirically tests the motives driving the structural transformation of China＇s technology export. The conclusions are： （1） the structure of China＇s technology export has improved significantly in recent years, but not as highly as measured by Rodrik （2006） et al. （2） The dynamic mechanism of the structure of China＇s technology export differs from that of the other developing countries. At national and regional levels, the mounting physical capital stock is the fundamental driving force, but with obvious decreasing marginal utility. （3） Excessive unskilled labor in the capital production sector in the central and western regions, and excessively low export prices in the eastern regions have caused negative effects of the skilled labor in the western region and unskilled labor in the eastern region on local structure of technology export.
