平板约束下激光诱导等离子体的动态仿真

为深入认识空间约束增强的物理机理,采用二维可压缩流体模型,建立平板约束下激光诱导等离子体动力学行为的数值模拟模型,计算了平板约束下等离子体的演化过程,得到的一系列时间分辨的温度分布结果与实验结果基本一致.揭示了平板约束下,反射激波对等离子体的压缩作用导致等离子体温度升高的机理.对不同激光能量和不同约束板间距对等离子体温度增强效果和增强时刻的影响进行了研究,两板间距增加,增强时刻明显延迟,等离子体温度的增强效果削弱.     

N离子注入对Ti—Al—Zr合金耐蚀性影响研究

经完全退火处理的Ti-Al-Zr合金表面注入不同剂量的N离子，并在pH值为10的溶液中进行电化学腐蚀试验。结果表明，N离子注入后，试样表面首先形成具有四方结构的ε-Ti2N，随着离子注入剂量的增加，四方结构的ε-Ti2N逐渐向立方结构的σ-TiN转变，X射线光电子能谱的分析结果也证实了这一变化过程；N离子的注入能明显改善Ti-Al-Zr合金表面的耐腐蚀性能，且在注入8×10^16 ion／cm^2时得到最佳的耐腐蚀性。根据原子碰撞理论对电化学腐蚀实验结果进行了理论分析。In the present investigation, fully annealed Ti-Al-Zr plates were implanted with different nitrogen fluences. The corrosion resistance was examined by the electrochemical methods in a solution with pH value of 10 at room temperature in order to determine the optimum fluenee that can give good corrosion resistance in a simulated nuclear reactor condition. The results show ε-Ti2N phase formed initially and then transformed into σ-TIN with increasing of nitrogen fluences, which was confirmed by the results of X-ray photoelectron spectroscopy （XPS）. In addition, it can be found the increase of the corrosion resistance depends on the nitrogen fluence employed and the maximum improvement of the corrosion resistance was observed with a fluence of 8 × 10^16 N^＋ ion/cm^2. The mechanism of the corrosion resistance is attributed to defect accumulation, formatio on of amorphous phase and nanocrystallization in the implanted layer.     

Ti-2Al-2.5Zr合金He离子辐照效应研究

 在Ti-2Al-2.5Zr合金中注入能量为75 keV的He离子，注入剂量分别为5×10¹⁶cm^-2，1×10¹⁷ cm^-2。通过显微硬度测量和剖面电子显微观察，研究了He离子对Ti-2Al-2.5Zr合金力学性能和显微组织的影响。结果表明:样品的显微硬度随He离子注量的增加而升高，在温度为350和550 ℃的Ar气中退火后硬度有所下降。剖面电子显微观察发现有位错环和He气泡生成，退火后He气泡有长大、缺陷有回复的趋势。辐照产生的位错环是辐照后硬度升高的直接原因，其退火发生回复又引起硬度随退火温度的升高而降低。