高能球磨制备纳米WC-8Co复合粉末

对采用高能球磨法制备纳米WC-8Co复合粉末的工艺条件进行了研究。实验采用逐步优化方式,研究液固比、球料比、球磨转速、球磨时间对粉末的特性的影响。采用SEM扫描电镜观察粉末形貌,用EDX能谱分析了粉末中Co元素的分布,检测了粉末中Co的化学成分,确定了液固比参数,通过检测粉末的比表面和BET粒度的变化优化球料比、球磨转速及球磨时间等工艺参数,采用最优化工艺得到了粉末比表面为6.82m2/g、BET粒度为59.4nm,Co相分布均匀的纳米WC-8Co复合粉末。     

添加钕对Mg2Ni储氢合金的结构和电极性能的影响

利用两步法制备了一系列添加Nd的三元Mg2-xNdxNi合金。XRD分析证实，当x=0．05，0．1时，制得的三元Mg2-xNdxNi合金均为Mg2Ni单相合金；三元Mg18Nd0．2Ni(x=0．2，0．3)合金为三相合金，三相分别为Mg2Ni，NdNi，NdMgNi4。模拟电池测试结果表明，同Mg2Ni合金相比，球磨10h的三元Mg1．8Nd0．2Ni合金和Mg17Nd03Ni合金电极的放电容量提高明显，且Mg17Nd03Ni合金电极的循环性能有明显改善。这极有可能与合金中NdMgNi4相的存在以及球磨形成的微结构有关。     

周铣加工表面形貌仿真新算法

考虑主轴偏心，基于周铣过程中刀具切削刃上任意点与工件相对运动的轨迹方程和周铣过程几何特征，构造出可以求解周铣加工表面上任意一点形貌高度值的三维表面形貌仿真算法，并给出了相应的仿真算例。该算法无需对刀齿进行微段离散，并且不依赖于工件网格划分，加工表面上任意一点形貌高度值的计算次数等于刀具齿数，具有通用性好、运算速度快、结果准确度高的特点。     

球磨工艺对Ti/HA复合材料原始粉料细化过程的影响

采用不同球磨介质对Ti+30％HA(质量分数)原始粉料进行高能球磨,研究了球磨工艺对 Ti／HA复合材料原始粉料细化过程的影响。研究结果表明:采用干磨工艺时,随着球磨时间的延 长,HA粉得到明显的细化,而Ti粉细化不明显,HA粉堆积覆盖在Ti粉大颗粒上;采用湿磨工艺 时,HA粉和Ti粉都明显细化,表明湿磨工艺可以提高球磨的细化效果,提高HA粉在Ti粉中的 均匀弥散分布程度。     

热机械法制备超细弥散分布钨铜复合粉末

本研究在对钨铜粉末共还原的基础上设计了一种热机械法来制备超细弥散分布钨铜复合粉末。对粉末通过SEM、XRD、粒度分析、氧含量及其烧结性能的研究 ,结果显示 :通过对钨铜高温氧化物粉末的短时快速球磨 (约 3～ 10小时 )后 ,复合粉末可在较低的温度下还原彻底 ,而且粉末粒度细小 (0 2 μm左右 ) ,分布均匀 ,比表面增加 ,具有极高的烧结性能。对比机械合金化工艺直接制备钨铜复合材料工艺得知 :对氧化物粉末进行了短时高能球磨 ,快速细化了氧化物粉末粒度 (<1μm) ,降低了粉末还原温度 (6 5 0℃ ) ,制备出高分散的超细钨铜复合粉末 (<1μm) ,在较低的烧结温度 (12 0 0℃ )下得到相对密度为 99 5 %、热导率为 2 0 5W·m- 1 ·K- 1 的钨铜复合材料制品。     

Preparation and Structure of Mg2-xRExNi （RE = La, Ce, Pr, Nd, Y） Ternary Alloys

A series of Mg2-xNdxNi (x =0.05, 0.1, 0.2, 0.3) alloys and Mg1.95RE0.05Ni (RE= La, Ce, Pr, Nd, Y)ternary alloys were prepared by ball milling of mixted powder of Mg, Ni, RE and sintering under the protection of argon. XRD analysis shows that Mg2-xNdxNi (x = 0.05, 0.1 ) and Mg1.95RE0.05Ni consist of single phase with the same crystal structure as Mg2Ni. While three-phase alloys including Mg2Ni, NdNi and NdMgNi4 were formed in Mg1.8Nd0.2Ni and Mg1.7Nd0.3Ni alloys respectively. The lattice constants of Mg2Ni in those ternary alloys were calculated. The decomposition of Mg2Ni occurs in the milling process of Mg2Ni and Mg1.95RE0.05Ni alloys respectively. For the latter, another earlier reaction occurs in milling process, which means that atoms of RE are separated from crystal structure of Mg2Ni and form relevant oxides by combination with oxygen existed in argon atmosphere.     

Structural and Electrochemical Characteristics of Mg0.94 La0.06 Ni AlloyPrepared by Ball Milling

The amorphous Mg0.94Lao.o6Ni alloy was synthesized by ball milling for different time at 400 r min^-1. Electrochemical performances of the alloy electrodes were investigated and the results show that the specimens would reach their maximum electrochemical discharge capacities at the first charge/discharge cycle. The cyclic tests and X-ray diffraction(XRD) results show that discharge capacities would decrease rapidly due to the crystallization of the amorphous and the oxidization of magnesium on the particle surface during the electrochemical charge/discharge cycling. In addition, the DTA and SEM results reveal that the thermal stabilities will be improved and the size of the alloy will be decreased with the ball-milling time. The amorphous Mgo.96Lao.04Ni alloy prepared by ball milling for 40 h at 400 r min^-1 shows the bestelectrochemical properties.     

Neural networks for estimating the tool path length in concurrent engineering applications

This paper deals with the development of a neural computing system that can predict the cutting tool path length for milling an arbitrary pocket defined within the domain of a product design, in a computer numerically controlled (CNC) setting. Existing computer aided design and manufacturing systems (CAD/CAM) consume significant amounts of time in terms of data entry pertaining to the geometries and subsequent modifications to them. In the concurrent engineering environment, where even the designer needs information from the CAD/CAM systems, such time-consuming processes can be expensive. To alleviate this problem, a neural network system can be used to estimate machining time by predicting cost-dependent variables such as tool path length for the pocket milling operation. Pockets are characterized and classified into various groups. A randomized design is described so that the training samples that have been chosen represent the domain evenly. An appropriate network was built and trained with the sample pocket geometries. The analysis of the performance of the system in terms of tool path length prediction for new pocket geometries is presented.     

Preparation of transmission electron microscopy cross-section specimens of crack tips using focused ion beam milling

The preparation of transmission electron microscope (TEM) thin foil specimens from metal alloys containing cracks is usually thwarted by the difficulty in preventing preferential erosion of material along the flanks and at the tips of cracks. Recent developments in focused ion beam (FIB) micromachining methods have the potential to overcome this inherent problem. In this article we describe the development of new procedures, one using FIB alone and the other using a combination of FIB with more conventional ion milling to generate TEM specimens that largely retain the microstructural information at stress corrosion cracks in austentic alloys. Examples of corrosion product phase identification and interfacial segregation are included to verify that detailed information is not destroyed by ion bombardment during specimen preparation.     

两类柱状回转铣刀NC加工的难点

介绍了球头柱状和带角圆柱状铣刀的设计与NC加工中相关主干模型，集中就这两类铣刀的难点——二轴联动NC加工中的径向进给和球头顶尖问题，给出了较为理想的处理方案。