铝电磁铸轧冷却区中电磁场行为探讨

介绍了铝电磁连续铸轧冷却区中电磁场的基本特性,探讨了电磁场在冷却区段的作用效果,分析了电磁场在该区中产生的几种磁势和电势,以及这几种磁势和电势的形态对铝熔体的影响,并描述了铝熔体中电子在这个区域的运动轨迹。     

Al/Ti液/固界面扩散溶解层形成机制及生长规律

采用镶嵌式扩散偶技术制备Al/Ti扩散偶,在Al熔点以上Ti熔点以下进行扩散热处理,研究Al/Ti液/固界面扩散溶解层的组织结构演变、形成机制及生长规律。实验结果表明,热处理后的扩散溶解层为TiAl3颗粒 和含少量Ti的铝基固溶体的混合组织;TiAl3相是热处理过程中最先出现也是唯一出现的新生相;扩散溶解层的生长机制和生长方向随热处理时间的延长发生了改变,在热处理开始后一段时间,扩散溶解层的生长受化学反应速度控制,与保温时间呈线性关系,之后,转变为受扩散控制,与保温时间呈抛物线关系,扩散溶解层的生长方向也由Ti基侧转变为Al基侧;扩散溶解层的厚度与热处理温度呈指数关系。     

裂纹尖端塑性区和无位错区的微观模拟

用细观断裂力学研究了刃型位错从Ⅰ型，Ⅱ型及Ⅰ Ⅱ复合型裂纹尖端沿多个滑移面的发射以及裂纹周围无位错区和塑性区的形状和大小．结果表明，Ⅱ型裂纹塑性区形状和宏观断裂力学算出的塑性区形状有所不同，而I型裂纹塑性区形状则类似；当外载荷相同时，Ⅱ型裂纹的塑性区比Ⅰ型裂纹的塑性区要大得多；复合型裂纹的塑性区形状和大小更接近Ⅱ型裂纹．各种裂纹尖端周围均存在无位错区，其形状与相应的塑性区相似。     

使用气电立焊中的体会

本文介绍船体焊接中,使用气电立焊的焊前检查,焊中注意事项,常规故障的处理及立缝的焊接工艺。     

Understanding the copper of the Statue of Liberty

Pierre-Eugène Secrétan, a French copper industrialist, donated the copper sheets for the construction of the skin of the Statue of Liberty when it was built in 1875–1876. It can be inferred from the history of Secrétan's activities that the sheets were rolled in his plant of Sérifontaine. The impurities found in two samples obtained from the U.S. National Park Service show that different qualities of copper were used. They indicate, by taking also into account the commercial relations of Secrétan, that the copper may possibly have come from Spanish or South/North American ore.     

Understanding the unique properties of SPD-induced microstructures

Refining microstructure by severe plastic deformation to a nanometer range changes fundamental properties, such as the Curie and Debye temperatures, and engineering properties of pragmatic significance, such as strength and ductility. These enhancements originate in the combination of very small grain sizes coupled with specific defect structures. Ongoing research is rapidly advancing the understanding of severe plastic deformation-induced microstructures, leading toward the commercialization of these materials. For more information, contact T.C. Lowe, Los Alamos National Laboratory, Materials Science and Technology Division, MD G754, Los Alamos, New Mexico 87545; (505) 665-1131; fax (505) 665-4584; e-mail tlowe@lanl.gov. Authors’ Note: All compositions are given in weight per cent.     

Electrodepositors and the Patent Law

The types of contamination and levels of concentration likely to be found in the atmosphere and rainwater are considered with reference to their effect on paint films. Specific action on paint includes slow drying, production of excessive water sensitivity, formation of crystalline bloom, yellowing and metallic staining. Pollution can also influence the rate of corrosion of steel.     

Temperature Gradient Zone Melting

Under certain conditions, a molten zone can be made to move through a solid by impressing a stationary temperature gradient across the solid. This phenomenon can be utilized in fabricating semiconductive devices, growing single crystals, joining, boring fine holes in solids, measuring diffusivities in liquids, small scale alloying, and purification. Fundamentals and exemplary applications are outlined.