Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-19 Cooperative journals: 《金属学报》
Abstract： Ni- based single crystal superalloys have been widely used for blades and vanes in gas turbine. However, recrystallization (RX) induced by residual strain has been a serious problem for the application of single crystal superalloys. In previous work, effect of microstructure, such as g', g/g' eutectics and carbides, as well as heat treatment parameters, on the RX behavior have been studied. However, the effect of alloy elements on the RX behavior has rarely been reported. Therefore, in this work, the effect of the important solution strengthening elements, W and Re, on the deformation and RX of solution heat treated Ni-based single crystal superalloys was investigated. At first, two single crystal superalloys were prepared, and W and Re were added into one alloy among them. After solution heat treatment, these two single crystal superalloys were deformed by shot-peening or Brinell indentation. Then these deformed samples were heat treated to observe the microstructure of RX. It indicated that RX depth decreased with the addition of W and Re irrespective of deformation mode and heat treatment temperature. Short time heat treatment experiment of indented and shot-peened samples both indicated that incubation period of RX was prolonged and nucleation of RX was slowed with the addition of W and Re, which verified that RX was suppressed by W and Re. After shot-peening, micro-hardness of the alloy with W and Re increased, but the depth of deformation zone was obviously reduced. Higher density of dislocation was found in the single crystal superalloy with W and Re, and also lots of dislocation tangles were observed. So, in this alloy, dislocation annihilated slowly, that is, recovery was slowed down, which prolonged the incubation period of RX. During the process of RX grain growth, the maximum RX grain boundary migration velocity was reduced with the addition of W and Re. Moreover, the change of mean RX grain boundary migration velocity showed the same trend with the micro-hardness along the direction of RX depth.
Subjects: Astronomy >> Astrophysical processes submitted time 2020-09-03 Cooperative journals: 《天文研究与技术》
Abstract： 2020年6月21日，我国境内发生了日环食，环食带经过西藏、四川、重庆、湖南、江西、福建和台湾，我国其他地方可见日偏食。深圳市天文台的太阳望远镜观测了日偏食的整个过程，同时，基地内的气象设备观测了太阳辐射、温度、湿度和气压等气象参素。日食期间太阳观测和气象要素观测的分析结果表明：（1）从日食初亏到食甚，太阳辐射、温度和气压均有下降，随后缓慢上升，受天气条件影响，极小值时刻相对于食甚时刻有滞后，其中，太阳辐射滞后1.37分钟，温度滞后6.37分钟，气压滞后10.37分钟；（2）从初亏到食甚，相对湿度先上升到极大值，然后持续33分钟，随后下降，极大值时刻相对于食甚时刻滞后6.37分钟；（3）对比日食前后两天气象要素变化，日食时太阳辐射、温度和相对湿度的变化率约比没有日食时高1个数量级，气压的变化率相差不大；（4）日食期间，日面相对强度和气象要素之间有很好的相关性，相关系数分别达0.95、0.89、-0.82和0.75。
Subjects: Geosciences >> Other Disciplines of Geosciences submitted time 2019-09-11 Cooperative journals: 《干旱区地理》
Abstract：基于自然与人文多重栅格数据，构建人居环境质量综合指数评价模型，分析2015年关中平原城市群人居环境的空间分异格局，并对人口分布与人居环境质量的协同性进行探讨。结果表明：(1)人居自然环境呈现出自东向西，由山地、高原向平原、谷地依次递减的空间分布格局，受地形影响最为明显，地形起伏度与人居自然环境呈负相关关系。(2)人居人文环境表现出平原低、山区高，城镇高于乡村的空间分布格局，受城市行政层级影响显著。(3)关中平原城市群人居环境综合质量指数介于0.216～0.716之间，呈现出以关中平原、汾河谷地向外梯级递减的带状空间分布格局。(4)关中平原城市群人口密度与人居环境质量空间分布显著一致，总体呈现出平原高于山地，城市高于乡村的空间分布规律，人居环境质量越高，人口密度越大，土地利用也越充分。
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