The phonon spectrum of ordered zincblende Si50Ge50 alloy is calculated by ab initio method. The energy band structure at zero pressure and the pressure dependence of phonon dispersion curves are shown up to 20 GPa. Th...The phonon spectrum of ordered zincblende Si50Ge50 alloy is calculated by ab initio method. The energy band structure at zero pressure and the pressure dependence of phonon dispersion curves are shown up to 20 GPa. The calculation finds a pressure-induced softening of the transverse acoustic phonon mode and the mode frequency reaching zero at about 14 GPa, which indicate breaking of the symmetry and formation of a new phase under high pressure.展开更多
采用高频感应炉熔炼制备Al-50Si合金,通过金相、热物理性能、SEM和能谱分析仪对不同参数下得到的Al-50Si合金缺陷和热物理性能进行测试分析。结果表明,当熔炼频率为930 Hz,用4 g C_2Cl_6精炼剂精炼一次时铸态宏观样貌较好。随着温度的升...采用高频感应炉熔炼制备Al-50Si合金,通过金相、热物理性能、SEM和能谱分析仪对不同参数下得到的Al-50Si合金缺陷和热物理性能进行测试分析。结果表明,当熔炼频率为930 Hz,用4 g C_2Cl_6精炼剂精炼一次时铸态宏观样貌较好。随着温度的升高,气体的溶解度变小,气体更容易从金属液中逸出所以930 Hz熔炼时效果较好;随着精炼次数和精炼剂单次用量的增加,气孔有逐渐变大的趋势。这是因为精炼时金属液剧烈翻腾不但会卷入新的气体,还可能会使金属液中的气孔逐渐聚集所以气孔会逐渐变大。铸造气孔的存在降低了材料的热导率,同时气孔的增加也使得材料的线膨胀系数变大。展开更多
文摘我们在大修 S150东德内圆磨床时,为了改善润滑条件,解决工作台低速爬行现象,除采取措施提高导轨几何精度、增强液压传动系统和机械传动部分刚性外,还把工作台导轨副由滑动导轨改成液压卸荷导轨。实践证明,对消除工作台低速爬行现象有显著效果。该机床工作台导轨为 V-平型导轨副,润滑油由专用润滑泵供给,床身导轨上开有 N
基金Supported by the National Natural Science Foundation of China (Grant No. 50771090)the State Key Program for Basic Research of China (Grant No. 2005CB724404)the Program for Changjiang Scholars and Innovative Team (Grant No. IRT0650)
文摘The phonon spectrum of ordered zincblende Si50Ge50 alloy is calculated by ab initio method. The energy band structure at zero pressure and the pressure dependence of phonon dispersion curves are shown up to 20 GPa. The calculation finds a pressure-induced softening of the transverse acoustic phonon mode and the mode frequency reaching zero at about 14 GPa, which indicate breaking of the symmetry and formation of a new phase under high pressure.
文摘采用高频感应炉熔炼制备Al-50Si合金,通过金相、热物理性能、SEM和能谱分析仪对不同参数下得到的Al-50Si合金缺陷和热物理性能进行测试分析。结果表明,当熔炼频率为930 Hz,用4 g C_2Cl_6精炼剂精炼一次时铸态宏观样貌较好。随着温度的升高,气体的溶解度变小,气体更容易从金属液中逸出所以930 Hz熔炼时效果较好;随着精炼次数和精炼剂单次用量的增加,气孔有逐渐变大的趋势。这是因为精炼时金属液剧烈翻腾不但会卷入新的气体,还可能会使金属液中的气孔逐渐聚集所以气孔会逐渐变大。铸造气孔的存在降低了材料的热导率,同时气孔的增加也使得材料的线膨胀系数变大。
