出访澳大利亚参加国际焊接学会第5届亚太地区会议报告

由澳大利亚焊接学会(Welding Technology Institute of Australia)主办的国际焊接学会第5届亚太地区会议(The 5th Asian Pacific ⅡW International Congress)于2007年3月7～9日在悉尼市奥林匹克海内外的186位代表参加了此次会议.     

河北长立:再制造让报废旧发电机修复如新

在一般人眼里,一台台锈迹斑斑的报废旧发电机没有任何价值,充其量只能回炉作原料,而在河北长立汽车配件有限公司,它们却是一个个不可多得的宝贝.经过拆解、基础件检测、修复等一道道工序,可让报废的发电机修复如新,再次勃发澎湃动力,而再制造后的成品的价格只有新品的70％,并可实现节能、节材.     

性能优异的氮化镓

英国剑桥大学的科林·汉弗莱斯拥有21世纪的"魔法石".他和世界各地的一批科学家都在研究炼金术上梦寐以求的东西:这种物质可以把普通金属变成金子,或者说金钱;它可以传送光线而不会将能量以热的形式浪费掉;它可以把手机信号扩大10倍,让电脑的速度提高1万倍.     

焊接盛会百家争鸣经济热点无限商机——第22届中国焊接博览会将为长三角经济注入新的活力

伴随江苏及长江三角洲国民经济的迅速发展,应我国焊接领域各界同仁的要求,2008年9月25～27日,第22届中国焊接博览会将在紫金山下玄武湖畔的南京国际展览中心隆重召开.中国焊接博览会组织委员会精心组织,细心论证,保持大会一贯优势并不断创新.作为我国唯一国字号焊接品牌展,本届大会在延续历届的特点之外,更有以下优势.     

光辉的三十年历程——贺华东地区热处理协作组成立30周年

1974年金秋季节,全国化学热处理学术交流会在武昌召开,出席会议的华东代表有江西省:胡立生、刘志德;安徽省石福占、张镇远;江苏省孙月芳、吴岚方;上海市沈百全、黄秀娟;浙江省高文龙、胡文辉;福建省林元盛、周良颖;山东省王世清、张文仁等同志,会上召开了组建"华东地区热处理协作组"座谈会并取得了一致意见,由江西省负责协作组的筹建工作.     

脆弱成本支撑下的锌价

在过去的五月,国内外期锌市场可谓是先扬后抑大幅度震荡.前不久,我国汶川发生的特大地震,导致锌市场出现局部供应中断刺激锌价大幅反弹,给人们些许的上涨希望;到了后半月,在LME 锌库存的激增以及美元重新走强的双重打击下,国内外市场锌价的破位下跌.截至6月2日,LME 三个月期锌盘中却一度击穿2006 年2 月以来每吨1970 美元的最低水平.国内沪锌期货在5月的最后一个交易日更是全线封跌停,随后就刷新了期锌上市以来的最低价,投资者都在思考锌价为什么跌得如此厉害呢?什么时候是个头呢?笔者认为锌市场的整体供需并没有实质性改变,成本的支撑显得脆弱无力,锌价的下跌趋势将延续,但波动将加剧!     

非凡诡异的古蜀国青铜造像——《中国古代艺术铸造系列图说》之十七

商代(公元前17世纪--前11世纪)晚期锡青铜 人像高171cm,底座高90cm 四川广汉三星堆遗址祭祀坑出土 1986年,川西平原的广汉市三星堆两个祭祀坑出土了数量众多的金器、青铜器、玉器、陶器、象牙器、海贝等,总数达一千余件.特别是非凡诡异的青铜神像和面具,被认为是"世界上最引人注目的考古发现", "把蜀文化上限向前推进了一千多年".     

V法铸造工艺设备和质量

真空密封造型是一种物理造型工艺方法。型砂中不加粘结剂、水和附加物，因而减轻了砂处理工作，而且造型和铸件落砂清理的劳动量也大大减少，旧砂回用率可达95％以上。原理是利用塑料薄膜密封砂箱，采用真空泵抽出型内空气，在铸型内外形成压力差，使干砂紧实，以形成所需型腔的一种物理造型方法。因此，真空密封造型又名“负压造型法”或“减压造型法”，简称为“V”法铸造。     

一个科研创造的神话--记宁波飞轿造漆有限公司科研所

"用醇酸树脂酯化废水生产各色调合漆的方法"已申请国家发明专利,如在全国造漆工业推广使用,保守估计,每年可为国家节约石油能源50万t;通过利用地沟废油,及化工厂废料PTA残渣可代替昂贵且不断上涨的多元剂造漆,而在此之前,PTA残渣因其具有污染性且永不腐烂,是令人头痛的工业残渣,只能深埋处理;油漆本是易燃品,但掺上一种独创的溶液后,着火处可把此种油漆当水泼上去灭火……     

制造业防锈防护工艺亟待提升

我国装备制造业金属制品的锈蚀问题,至今仍很突出.据中国腐蚀与防护学会理事长柯伟院士编著的《中国腐蚀调查报告》统计,2000年,我国年腐蚀损失达5 000亿元人民币,约占国民生产总值的5%.而美、英、德国家的年腐蚀损失分别只占国民生产总值的2.76%、3.5%和3%.从发达国家的经验和数据来看,其中1/4以上的锈蚀损失可以通过防腐蚀手段进行控制.我国如果持续发展防腐蚀新技术、新工艺和新产品,提高目前的防锈包装水平,可减少锈蚀损失1 000亿元人民币.     

Effect of Spark-Plasma-Sintering Conditions on Tensile Properties of Aluminum Matrix Composites Reinforced with Multiwalled Carbon Nanotubes (MWCNTs)

In this study, aluminum (Al) matrix composites containing 2 wt.% multiwalled carbon nanotubes (CNTs) were fabricated by powder metallurgy using high-energy ball milling (HEBM), spark plasma sintering (SPS), and subsequent hot extrusion. The effect of SPS conditions on the tensile properties of CNT/Al composites was investigated. The results showed that composites with well-dispersed CNTs and nearly full-density CNT/Al can be obtained. During HEBM, CNTs were shortened, inserted into welded Al powder particles, bonded to Al, and still stable without CNT-Al reaction. After consolidation, Al₄C₃ phases formed in composites under different sintering conditions. With the increase of sintering temperature and holding time, the strength decreased. Conversely, the ductility and toughness noticeably increased. As a result, a good balance between strength (367 MPa in ultimate tensile strength) and ductility (13% in elongation) was achieved in the as-extruded CNT/Al composite sintered at 630°C with a holding time of 300 min.     

高能球磨法制备的碳纳米管增强铝基复合材料的微观组织和力学性能

采用高能球磨法制备了不同体积分数的碳纳米管(CNT)与Al粉的混合粉末,用粉末冶金工艺制备了CNT/A1复合材料.微观结构分析表明.球磨可以分散一定含量的CNT到Al基体中,并与其产生良好结合.在适当的球磨工艺下.球磨不会造成CNT的严重损伤.拉伸实验表明,CNT体积分数为1.5%时,力学性能达到了最高值,屈服强度相对于纯A1基体提高了53.6%.而CNT体积分数为3%时,形成了大量的CNT团聚,力学性能迅速下降.CNT/A1复合材料的主要强化机制为细晶强化和载荷传递.     

混杂增强(CNTs+TiB2)/Cu复合材料制备与性能

本文以碳纳米管（CNTs）和TiB2颗粒作为增强相,首先利用球磨、表面吸附和热压烧结相结合技术制备具有层叠结构的CNTs/Cu复合材料,改善了CNTs在铜基复合材料中易团聚问题。CNTs/Cu复合材料的致密度和导电率随CNTs含量增加而降低,抗拉强度和伸长率随CNTs含量增加先升高后降低,当含量为0.1 wt.%时综合性能最优,致密度、导电率和抗拉强度分别为97.57%、91.2 %IACS和252 MPa。而球磨后热压烧结的1 wt.% TiB2/Cu复合材料致密度、导电率和抗拉强度分别为97.61%、58.3 %IACS和436 MPa。在此基础上,将TiB2颗粒原位引入到具有层叠结构的CNTs/Cu复合材料,制备获得混杂增强(CNTs+TiB2)/Cu复合材料。相比单一CNTs（或TiB2）增强铜基复合材料,(CNTs+TiB2)/Cu复合材料的强度提升显著。其中,(0.1 wt.% CNTs+1 wt.% TiB2)/Cu复合材料的导电率和抗拉强度分别为56.4 %IACS和531 MPa,相比1 wt.% TiB2/Cu,其导电率仅降低3.3%,而抗拉强度则升高21.8%。这主要归因于片层间CNTs可起承担和传递载荷作用,同时片层间弥散分布的TiB2颗粒可以钉扎位错,两种强化机制共同作用使(CNTs+TiB2)/Cu复合材料的抗拉强度显著提升。     

Processing and characterization of carbon nanotube mat/epoxy composites

A carbon nanotube mat (CNT mat) with long (∼1 mm) multi-walled carbon nanotubes (MWCNTs) was used to process MWCNT/epoxy composites at high concentrations (4.4 and 10.0 wt.%) of MWCNTs by a simple method without the use of a solvent. The CNT mat circumvents several cumbersome processing steps, including the dispersion of CNTs in a solvent. Two different resin-impregnation processing methods were explored. The processing steps were chosen to prepare composite samples based on the performance of the composites and the simplicity of the processing techniques. Scanning electron microscopy (SEM) was used to examine the microstructures of the CNT mat and its composites. The mechanical and electrical properties were tested. The tensile strengths of the composites with 10.0 wt.% MWCNTs were increased by 17% to 90% when compared to that of neat epoxy samples. The electrical conductivity of the composite is 36.1 S/cm. 4.4 wt.%-MWCNT composites show very large strain valuesupon fracturing (> 15 %), and their electrical conductivity is 14.9 S/cm. These results show that CNT mat/epoxy composites can be used as flexible electrodes and as a matrix system for advanced fiber composites.     

Al2O3弥散强化铜-锡含油轴承的制备和性能

以内氧化法制备的Al2O3弥散强化铜(简称“弥散铜”)粉和雾化锡粉为原料,采用扩散合金化法制备弥散铜-锡合金粉末,经压制、烧结制备弥散铜-锡含油轴承,研究扩散温度对弥散铜-锡粉末合金化程度的影响,并考察烧结温度对含油轴承性能的影响。结果表明:弥散铜-锡混合粉末经700℃扩散处理后,锡在弥散铜基体中分布均匀,制备的弥散铜-锡合金粉末的松装密度为2.40 g/cm3、流动性为39.6 s(50 g);轴承压坯在800℃及以下温度烧结时,粉末颗粒之间没有发生显著烧结,导致轴承性能较差。当烧结温度为850℃时,粉末颗粒之间形成一定的冶金结合,轴承强度显著提升,开孔率小幅降低。在900℃及以上温度烧结时,轴承发生显著收缩,开孔率明显降低。850℃烧结制备的弥散铜-锡含油轴承的径向、轴向尺寸变化率均约为1.0%,压溃强度为160 MPa,显微硬度为166 HV0.05,开孔率为26.0%。     

高能球磨结合粉末冶金法制备碳纳米管增强7055Al复合材料的微观组织和力学性能

采用高能球磨结合粉末冶金工艺制备了碳纳米管(CNT)含量(体积分数)分别为0、1%和3%的CNT/7055Al复合材料。采用OM、SEM、TEM以及拉伸实验等方法研究了CNT/7055Al复合材料的CNT分布、晶粒结构、近界面结构及力学性能,分析了复合材料的强化机制和各向异性。结果表明,CNT/7055Al复合材料为无CNT的粗晶区与富集CNT的超细晶区组成的双模态晶粒结构;CNT在Al基体的超细晶区中分散良好,CNT-Al界面干净清洁,界面反应产物少;3%CNT/7055Al复合材料沿挤压方向的抗拉强度达到816 MPa,但延伸率仅为0.5%。细晶强化和Orowan强化是CNT/7055Al复合材料主要的强化机制。由于CNT沿不同方向的增强效率不同以及粗晶条带组织的存在,复合材料表现出比基体合金更强烈的各向异性,在垂直挤压方向的拉伸性能要弱于沿挤压方向的拉伸性能。     

Strengthening of C/SiC Composites by Electrophoretic Deposition of CNTs on a SiC Coating

The current study reports the enhancement of mechanical properties of carbon fiber-reinforced silicon carbide ceramic matrix composites (C/SiC CMCs) by the application of a carbon nanotube/silicon carbide (CNT/SiC) coating. CNTs were deposited on the surfaces of C/SiC composites using electrophoretic deposition (EPD), after which infiltration by SiC was achieved through a chemical vapor infiltration process. An EPD duration of 5 min was associated with a 40% increase in the ultimate flexural strength relative to that of composites with a pure SiC coating. The observed enhancement was rationalized by the microstructural observations of SiC infiltration into the porous CNT morphology and the subsequent formation of CNT/SiC layers on the surfaces of the composites and by the inherent toughness of the SiC whiskers. The flexural strength decreased with EPD durations greater than 5 min due to the formation of thick CNT meshes, which decreased the open porosity and thereby obstructed further SiC infiltration. This is a viable methodology for the improvement of mechanical properties of CMCs by the introduction of a ceramic coating containing CNT.     

The comparison of W/Cu and W/ZrC composites fabricated through hot-press

In this study the W/Cu and W/ZrC composites have been fabricated by hot-press and then their mechanical properties were compared in addition to their ablation resistance. To produce W-20vol.%Cu composite at first stage the elemental W and Cu powders were ball milled for 3 h in rotation speed of 200 rpm, in which 2% nickel was added in order to reduce the density. The mixed powders were hot-pressed for 1 h at 1400 °C and compact pressure of 30 MPa. Additionally W/40vol.%ZrC composite has been fabricated by hot-pressing of mixed W and ZrC powders in 30 MPa and 2200 °C for 1 h. Since these materials are used at elevated temperature applications, where ablation is the main source of material failure, after producing the composites their ablation resistance was evaluated in a real condition. The results show that not only W–ZrC composite is better than W–Cu composite in mechanical properties, but also in ablation resistance.     

Investigation of the interfacial reaction between multi-walled carbon nanotubes and aluminum

Aluminum (Al)/carbon nanotube (CNT) composite films were fabricated by sputtering pure Al on the surface of aligned multi-walled CNT arrays. Heat treatment was performed in the temperature range 400–950 °C. The interfacial reaction between the Al and the CNTs was investigated by annealing the samples at various temperatures. The results indicated that aluminum carbide (Al₄C₃) was formed at the interface between the Al and CNT layers, and microscopy observation revealed that the reaction generally occurred at locations containing an amorphous carbon coating, at defect sites, and at open ends of CNTs. Because the nanosized CNTs are precursors for carbide formation, the Al₄C₃ formed is also nanoscale in size. The carbide formed on the surface as well as on the tips of the CNTs improves the interfacial interaction between the CNTs and the Al layers. This also contributes to the enhancement of the mechanical properties of the composite. Our investigation demonstrated that chemical vapor deposited CNTs are a suitable candidate as reinforcing material for Al and other metal matrices.     

Carbon nanotube reinforced aluminum composite fabricated by semi-solid powder processing

Semi-solid powder processing (SPP) is a promising technology that combines the benefits of semi-solid forming and powder metallurgy. In this study, carbon nanotube (CNT) reinforced aluminum alloy 6061 (Al6061) composite was synthesized by SPP for the first time. Mechanical alloying was used to disperse the CNTs in the matrix phase. The effects of the processing temperature (600 °C, 620 °C and 640 °C) on the microstructure, hardness, fracture surface and composition of the Al6061-CNT composite were investigated. Overall, the Al6061-CNT composite showed full densification above 99% with 100 MPa of pre-compaction and 50 MPa of pressure during consolidation in the semi-solid regime. Microstructure and the fracture surface analyses showed that the CNTs were uniformly dispersed throughout the Al6061 matrix. Higher density composite was obtained at higher liquid content, although the highest composite hardness was achieved when processed at 620 °C. It was speculated that the formation of carbides at higher temperatures affected the interface bonding between the matrix and CNT. The study showed feasibility of manufacturing CNT reinforced metal composites by SPP.