Net shape formation of sub-micron alumina with reduced flaws by high-speed centrifugal compaction process

A new compacting method for powder materials is presented. High-Speed Centrifugal Compaction Process (HCP) utilizes centrifugal force of about 10,000 g for the compaction. HCP is suitable for net shape compaction of fine sub-micron and nano-powders. HCP possesses a unique compacting mechanism that is different from other colloidal processes including Pressure Casting (PC), and has a number of useful characteristics. HCP has a higher compacting speed than PC, wide applicability for net shape formation, as well as a defect removing function. Because of homogeneous and flawless green microstructure, HCP alumina shows superior sinterability and higher strength and hardness than most of other aluminas. This article is based on a presentation made in the symposium “The 3rd KIM-JIM Joint Symposium on Advanced Powder Materials“, held at Korea University, Seoul, Korea, October 26–27, 2001 under auspices of The Korean Institute of Metals and Materials and The Japan Institute of Metals.     

涡流检测技术在宝钢热轧轧辊上的应用

介绍了轧辊涡流检测仪的工作要求、设备组成和使用方法,指出对轧辊进行涡流检测可防止爆辊,减少轧辊磨削量。     

冷轧处理线卷取机带头定位精度的改进

针对采用带头与卷取机芯轴橡胶套筒定位区动态接触的传统自动定位技术控制效果不好而带来带头印缺陷的问题，对其产生原因进行了分析，这是因为不同规格、钢种带钢的工艺参数不同，带钢穿带过程中在传送辊上的打滑量不同，在传输通道上的下垂量不同，带头到达卷取机芯轴定位区时计算带头位置与实际带头位置存在不稳定的偏差，因此带头定位精度不稳定。为此，开发了双动态自动定位技术，穿带过程中预留了足够的带钢打滑及下垂富余量，且带头与定位区中心线在助卷皮带咬入口静止状态下接触，消除了影响带头定位精度的主要因素，带头定位精度能稳定在±15 mm的误差范围内。实际应用效果表明，该方法可行、实用。     

THEORETICAL CALCULATION OF POINT DEFECTS IN Ni_3Al

Equilibrium equation of point defects in Ll_2 type intermetallic compounds was established tocalculate the relations of the concentration of antisite defects and vacancies and bulk composi-tion in Ni_3Al.The examination of temperature effects on the point defects cleared up the mis.understanding of the properties of the“constitutional point defects”in Ni_3Al.     

铸件缺陷修补方法

简述了铸件缺陷的谷种修补方法及工艺，指出液膜溶解扩散焊是一种比较先进的焊补方法。     

石墨的球状生长--球墨铸铁基础理论的最新发展(二)

球形晶体的结晶学条件要求雏晶必须有大量辐射对称的小角分枝;此外,这些小角度分枝应具备“规则分枝”特征（即相同的生长习性与生长速度）。在众多球化理论中,缺陷生长理论较符合球形晶结晶学原理,而石墨的缺陷生长与溶液结晶时的过冷有密切关系,化学成分、冷却速度等工艺因素都通过动力过冷、成分过冷、热学过冷影响石墨螺型缺陷决定最终生长成的石墨形状。对石墨球在奥氏体晕圈（壳）包围下生长过程进行了研究。用彩色金相方法揭示出奥氏体壳的形成过程并将奥氏体壳分为快封闭、慢封闭、不封闭三种类型,讨论了它们与石墨畸变的关系。快封闭的奥氏体壳保证得到圆整的石墨球,慢封闭与不封闭都使石墨形成畸形。     

304不锈钢精铸件点缺陷的形成与控制

针对典型304不锈钢精密铸件内出现的黑色点缺陷,对其表面形貌、成分进行了分析,并在此基础上总结了缺陷的形成机制,确定了相应的防止措施。研究结果表明,铸件内的点缺陷可以划分为两类:一类具有不规则截面,为脱蜡过程中剩余腊料的燃烧残留物;另一类为熔炼过程中,由于脱氧剂和除渣剂的去除不彻底而引入的夹杂。通过优化脱蜡和熔炼工艺,使得铸件内的点缺陷得到了很好的控制。     

数控小孔冲床网眼平板加工中的波浪纹缺陷成因分析及排除

文章就数控小孔冲床加工纺织烘干设备中帘子网眼平板产生波浪纹缺陷的原因,进行了全面、详细的理论分析.在排除机床、模具精度影响的基础上,针对压料机构运动误差产生的机理和不利影响,详细分析了网眼冲孔加工产生波浪纹缺陷的根本原因,提出了相应的改进措施,在实践中具有良好的实用效果.     

A modified embedded-atom method interatomic potential for the Fe–H system

A modified embedded-atom method (MEAM) interatomic potential for the Fe–H binary system has been developed using previously developed MEAM potentials of Fe and H. The potential parameters were determined by fitting to experimental data on the dilute heat of solution of hydrogen in body-centered cubic (bcc) and face-centered cubic (fcc) Fe, the vacancy–hydrogen binding energy in bcc Fe, and to a first-principles calculation for the lattice parameter and bulk modulus of a hypothetical NaCl-type FeH. The potential accurately reproduces the known physical properties of hydrogen as an interstitial solute element in bcc and fcc Fe. The applicability of the potential to atomistic approaches for investigating interactions between hydrogen atoms and other defects such as vacancies, dislocations and grain boundaries, and also for investigating the effects of hydrogen on various deformation and mechanical behaviors of iron is demonstrated.     

ZnO压敏陶瓷的非线性功能添加剂

本文采用单元掺杂与多元掺杂的方法，系统研究了几种过渡金属氧化物添加剂在控制ＺｎＯ压敏陶瓷非线性方面的作用，并根据金属阳离子外壳层电子结构稳定性和缺陷化学反应进行了分析，认为阳离子具有不饱和外层电子结构且半径与Ｚｎ＾２＋离子相近的过渡金属氧化物能改善ＺｎＯ压敏陶瓷非线性。