双能γ射线吸收法是一种检测弥散燃料元件铀均匀性的新方法。实验选用75Se多能谱γ射线源中的2个分支比较高的能量136、264 ke V进行测试;选用高纯锗(HPGe)探测器进行γ射线探测。根据U、Zr的γ射线衰减系数差异在136 ke V能量下远大于2...双能γ射线吸收法是一种检测弥散燃料元件铀均匀性的新方法。实验选用75Se多能谱γ射线源中的2个分支比较高的能量136、264 ke V进行测试;选用高纯锗(HPGe)探测器进行γ射线探测。根据U、Zr的γ射线衰减系数差异在136 ke V能量下远大于264 ke V能量的特性,测定U-Zr弥散燃料芯体中的U、Zr含量和均匀性。实验使用有机玻璃瓶罐装U粉末、Zr粉末制作标准样进行吸收系数标定,使用"迭代法"对方程进行求解。最终结果显示测试相对精度为±5%,满足大多数工程应用要求。展开更多
An Al-Mn-Fe-Si model alloy was subjected to two homogenization treatments, to achieve materials with different levels of Mn in solid solution and dispersoid densities, followed by cold rolling and back-annealing. Char...An Al-Mn-Fe-Si model alloy was subjected to two homogenization treatments, to achieve materials with different levels of Mn in solid solution and dispersoid densities, followed by cold rolling and back-annealing. Characterization of homogenization and deformation structures with respect to the effect of different microchemistries and strains on the structures was performed. Time-temperature-transformation （TTT） diagram with respect to precipitation and recrystallisation as a basis for analysis of the degree of concurrent precipitation was established. The TTT-diagram shows a strong effect of Mn concentration in solid solution and dispersoid density on the softening behavior. Recrystallization which finishes without the effect of concurrent precipitation results in an even, fine and equiaxed grain structure. Precipitation prior to or during recrystallization （concurrent） does retard the softening kinetics and leads to a coarse grain structure. However, the effect also depends on the duration of recrystallization and amount of precipitation. Recrystallization proceeding over a long time combined with a large amount of concurrent precipitation has a strong effect, otherwise the effect will be limited. Pre-existing fine and dense dispersoids （mean size 0.1 μm） before back-annealing do also lead to a coarse grain structure after recrystallization no matter whether additional concurrent precipitation occurs.展开更多
文摘本文提出了以计算多弥散体散射光强分布的一种递推公式,目的在于减少对Mic 系数 a_1、b_1和π_1、τ_1的计算工作量.计算了几种散射截面,其结果与有关文献的数据符合很好.计算中发现,Mic 无穷级数的收敛性与微粒的相对折射率的关系不明显,但与无因次直径α有关.并得出相对散射光强 I/I_0-散射角θ、无因次直径α及相对折射率 m 的三组曲线,其中,把根据 Fraunhofer 衍射理论计算的曲线与根据 Mic 散射理论计算的曲线作了比较,可以看出,当用 Fraunhofer 衍射理论代替 Mic 散射理论处理散射问题时,是可以找到参数(θ、α、m)的适用范围的,并且能确定其误差的大小.
文摘双能γ射线吸收法是一种检测弥散燃料元件铀均匀性的新方法。实验选用75Se多能谱γ射线源中的2个分支比较高的能量136、264 ke V进行测试;选用高纯锗(HPGe)探测器进行γ射线探测。根据U、Zr的γ射线衰减系数差异在136 ke V能量下远大于264 ke V能量的特性,测定U-Zr弥散燃料芯体中的U、Zr含量和均匀性。实验使用有机玻璃瓶罐装U粉末、Zr粉末制作标准样进行吸收系数标定,使用"迭代法"对方程进行求解。最终结果显示测试相对精度为±5%,满足大多数工程应用要求。
基金Project (KMB:193179/I40) supported by the Research Council of Norway
文摘An Al-Mn-Fe-Si model alloy was subjected to two homogenization treatments, to achieve materials with different levels of Mn in solid solution and dispersoid densities, followed by cold rolling and back-annealing. Characterization of homogenization and deformation structures with respect to the effect of different microchemistries and strains on the structures was performed. Time-temperature-transformation （TTT） diagram with respect to precipitation and recrystallisation as a basis for analysis of the degree of concurrent precipitation was established. The TTT-diagram shows a strong effect of Mn concentration in solid solution and dispersoid density on the softening behavior. Recrystallization which finishes without the effect of concurrent precipitation results in an even, fine and equiaxed grain structure. Precipitation prior to or during recrystallization （concurrent） does retard the softening kinetics and leads to a coarse grain structure. However, the effect also depends on the duration of recrystallization and amount of precipitation. Recrystallization proceeding over a long time combined with a large amount of concurrent precipitation has a strong effect, otherwise the effect will be limited. Pre-existing fine and dense dispersoids （mean size 0.1 μm） before back-annealing do also lead to a coarse grain structure after recrystallization no matter whether additional concurrent precipitation occurs.
