NdFeB磁体耐盐雾腐蚀行为研究

通过中性盐雾(NSS)腐蚀试验,对比分析了烧结Nd Fe B磁体和热变形Nd Fe B磁体在NSS腐蚀环境中的耐蚀行为。研究结果表明,Nd Fe B永磁体的盐雾腐蚀进程可分为两个阶段:腐蚀增重期和失重期,并给出了相应的腐蚀反应速率方程。在NSS腐蚀环境中,热变形Nd Fe B磁体表现出更好的耐蚀性,其失重比高矫顽力烧结磁体降低了30%,认为热变形Nd Fe B磁体具有特殊的片状纳米晶组织结构,富Nd相的晶粒更加细小,分布更加均匀,使得发生晶间腐蚀的通道更窄,从而抑制了腐蚀速率,提高了磁体基体的耐蚀性。     

Nd-Fe-B磁体烧结致密化过程的研究

定量描述了Nd-Fe-B磁体的烧结致密化过程, 分析了有效稀土含量、合金粉末粒度与烧结致密化过程的关系, 讨论了Nd-Fe-B磁体烧结过程的致密化机制. Nd-Fe-B磁体烧结致密化过程可分为3个阶段, 即致密化过程迅速进行阶段、缓慢进行阶段、相对稳定阶段;随着烧结温度的上升, 第一阶段表现得更为突出, 第二阶段对应的烧结时间区段大大缩短. 有效稀土含量的提高、合金粉末粒度的减小显著促进Nd-Fe-B磁体烧结致密化过程. 主相颗粒重排以及主相颗粒长大与形状适位性变化是Nd-Fe-B磁体烧结过程的两类主要致密化机制, 而且后者对于Nd-Fe-B烧结磁体实现完全致密化起着决定性的作用.     

烧结Nd-Fe-B磁体的温度稳定性缺陷分析

采用SEM、EDAX及粒度分析手段,研究了烧结Nd-Fe-B磁体开路磁通不可逆损失(hirr)异常偏高的原因。结果表明,磁体显微组织中晶粒尺寸分布不均匀及存在少量粗大晶粒,是导致其温度稳定性缺陷的主要因素,表现为少数产品hirr异常偏高。在磁体工业生产过程中,改进原料的铸锭和制粉技术,避免出现粗大粉末颗粒,减少极细粉末颗粒的数量,保证磁体显微组织精细均匀,是制备温度稳定性高的烧结Nd-Fe-B磁体的基本措施。     

等离子喷涂纳米ZrO2热障涂层的耐盐雾腐蚀性能

对大气等离子喷涂技术制备的纳米ZrO2热障涂层进行盐雾试验,采用金相显微镜、X射线衍射仪、拉伸试验机等对试验前后涂层组织及性能进行了研究。结果表明,纳米ZrO2热障涂层具有优异的耐盐雾腐蚀能力,盐雾腐蚀对涂层的显微组织、相结构、结合强度、剪切强度和耐湿热环境能力均无明显影响。盐雾腐蚀前后纳米ZrO2陶瓷面层均由t-ZrO2单相组成,其孔隙率分别为13.1%和12.6%,平均结合强度分别达到47.9MPa和48.7MPa。湿热试验后涂层完整、表面清洁,无新相生成。     

烧结Nd-Fe-B磁体表面多弧离子镀Ti(Al)N镀层性能研究

以烧结Nd-Fe-B磁体为基体,采用多弧离子镀,通过调节氮分压比获得不同颜色和性能的TiN和TiAlN镀层薄膜。利用X射线衍射仪、金相分析技术、盐雾试验和维氏硬度计等研究镀层薄膜的宏观和微观形貌、维氏硬度和耐腐蚀性能。研究结果表明,TiN和TiAlN镀层薄膜都能够极大地提高烧结Nd-Fe-B磁体的防腐蚀性能;TiN镀层中,氮分压比增加会使TiN镀层薄膜的颜色加深,氮氩比为1∶1时镀层薄膜的结合力和防腐蚀性能最好;而TiAlN镀层的结合力和耐腐蚀性能明显优于TiN镀层。     

烧结过程对Nd-Fe-B永磁材料磁性能与力学性能的影响

分析了烧结过程对Nd-Fe-B永磁材料磁性能和力学性能的影响.当烧结温度为1 373 K时,随烧结保持时间延长,材料剩磁Br先增加后趋于稳定,矫顽力Hci直线下降.成分为Nd25.5Pr7.5FebalNb0.45Cu0.2Al0.55B1.10的磁体样品的抗弯强度在烧结时间为5 h时达到一个最大值后便持续下降,而成分为Nd25.5Pr7.57.5FebalNb0.15Cu0.25Al0.75B1.10的磁体样品抗弯强度是持续下降的.试验结果表明:通过优化合金成分和烧结工艺参数,可以改善烧结Nd-Fe-B永磁材料的磁性能和力学性能,获得综合性能较高的磁体.     

添加Dy、Nb对烧结NdFeB磁体结构与性能的影响

采用SC工艺制备了Nd-Fe-B合金铸片,研究了在合金铸片中添加Dy、Nb元素对合金铸片显微结构和烧结Nd-Fe-B磁体磁性能的影响,确定了Nd-Fe-B磁体获得最佳磁性能时Dy元素、Nb元素的含量,并用扫描电镜、磁性能测量仪等对其进行了分析和测量。实验结果表明,Dy元素的添加可以使晶粒细小化、均匀化、规则化,在不显著影响剩磁的情况下大幅度提高磁体的内禀矫顽力;在含Dy元素和Co元素的磁体中加入少量Nb元素可以在不显著影响剩磁的情况下较大幅度提高磁体的内禀矫顽力,降低磁通不可逆损失,提高磁体使用温度。     

无重稀土烧结Nd-Fe-B磁体的显微结构和磁性能研究

对Ga、Al、Cu和Zr共同掺杂的烧结Nd-Fe-B磁体磁性能和显微结构进行研究，并通过回火工艺对磁体的矫顽力进行调控。结果表明：当一级回火为900℃×150 min,且二级回火为500℃×180 min时，磁体矫顽力H_cj从烧结态的14.33 kOe大幅提高到二级回火态的19.86 kOe,提高了38.6%;方形度H_k/H_cj由0.86增加到0.97;剩磁B_r仅从烧结态13.51 kGs略微下降到二级回火态的13.46 kGs;富稀土相分布更加连续和明显。研究分析表明，矫顽力大幅增加主要是由于含有少量的富Nd相和贫B相的烧结Nd-Fe-B磁体中Ga的掺杂改变了晶界相湿润性，降低了富稀土相中Fe元素的含量。本研究为无重稀土高矫顽力和高剩磁烧结Nd-Fe-B磁体步入产业化夯实了理论基础。     

动态压缩下烧结Nd-Fe-B磁体的断裂行为研究

采用分离式霍普金森压杆(SHPB)对不同型号的烧结Nd-Fe-B试样进行了动态压缩试验,利用扫描电子显微镜(SEM)对回收试样的微观断口形貌进行观察。试验结果表明,在压缩载荷作用下,使试样断裂产生的功可以用来表征试样的冲击稳定性。随着加载应变率的逐渐增大,试样的初始断裂时间逐渐减少,并且在单位体积下所做的功也逐渐减小,说明磁体的抗压强度随着应变率的增大而逐渐减小;磁体断裂时的破坏应力逐渐增大,而破坏应变逐渐减小。不同型号的烧结Nd-Fe-B磁体均表现出明显的脆性断裂特征,断裂方式主要是沿晶断裂。     

新型耐候性处理钢板的开发

耐大气腐蚀钢作为无维护的结构用材被广大用户所注目。在实际运用中,由于钢材表面自然形成最终稳定锈层需要较长时间（约需用10年以上）,而且在盐雾环境中不形成稳定锈层,这对有效发挥耐大气腐蚀钢的优点是不利的。为解决这些问题,日本《住友金属》Vol．slNO．1（998）报道了岸川浩史等人运用Cr置换稳定锈层中的Fe,形成结构微细致密的锈a－（Fe;人C）00H的新认识,开发出了加速生成最终稳定锈层的耐候性功能处理的新技术,这使得防止初期演变锈的产生,在盐雾侵袭环境中能形成稳定锈层。众所周知,耐大气腐蚀钢是一种添加少量能提…     

熔炼次数对M17返回料合金成分、组织和性能的影响

实验结果表明,M17铸造高温合金(%:0.16C、8.79Cr、5.79A1、4.93Ti、3.29Mo、15.20Co、0.78V、0.015B、0.073Zr、0.002S、0.001P、0.001 1O、0.001 0N)经25 kg真空感应炉返回重熔后,Si含量随重熔次数的增加而略有增加,合金中主要元素和其它杂质元素S、P、H的含量变化不大,而氧、氮略有增加;合金中初生碳化物由新合金中的草书体逐渐向返回合金块状转变,初生碳化物的遗传性堵塞合金凝固时的补缩通道,使返回料合金的疏松倾向增大,高温塑性下降较大。     

China's Major Non-ferrous Metals Imports & Exports

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Zinc Production by Province in 2014

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80% of Chinese Firms Purchasing Overseas Mines Ended up in the Red

<正>Minmetals Resources acquired the world’s largest copper mine under construction for USD5.85 billion.One after another,listed companies Jien Nickle,China Molybdenum and Chihong Zinc and Germanium raised money to get involved in overseas mining projects…SOEs and private enterprises are engaged in a frenzy of overseas mine purchasing.A reporter with Economic     

Copper Processing Profit Dropped Sharply,Copper Consumption Will Face Impact in the Second Half of the Year

正Judging from China’s copper consumption field,the biggest consumption unit is electric power,which accounts for 47%of total consumption;it is followed by light industry sector,including household electrical appliance,machinery,durable goods and hardware etc,which accounts for 22%of total consumption;followed by transportation field,     

Central Geological Prospecting Fund Newly Added 16.47 Million Tonnes of Bauxite in 2013

正In 2013,the Central Geological Prospecting Fund(CGPF)Project newly discovered 15 ore fields,including 3 large above ore fields,and 5medium sized ore fields.The reporter learned from the recently published"Annual Report of Central Geological Prospecting Fund Project(2013)"that,from 2006 to 2013 the CGPF     

Manufacturers of Copper Tube for Central Air Conditioner Use Face Mounting Pressure in the Final Quarter of the Year

正This year,the investment growth rate of real estate industry continued to slow down,sold area of commercial housing also dropped significantly,which brought huge pressure to the domestic air conditioning manufactures.In the first half of the year,by relying on high growth in national financial expenditure,along with investment in public infrastructure     

Xinjiang Ranks No.1 in Production of Primary Aluminum in China

正Kang Yi,Honorary Chairman of China Nonferrous Metals Industry Association,said recently at the Forum on Development of the Non-ferrous Metals Industry in Central and Western China held in Zhengzhou that,as more and more electrolytic aluminum factories in Xinjiang came into operation,the electrolytic aluminum output of Xinjiang had reached2,275,000 tons in the first 7 months this year,     

Shenhuo Coal Industry and Electricity Power Completed800,000 t/a Aluminum Project in Xinjiang

正"Xinjiang project has been completed according to schedule,but total completion and total start of production are two different concepts,after completion it still needs a gradual process of reaching production target."On the morning of November 3,Shenhuo Coal Industry and Electricity Power told investors the above statement on the investor interaction platform.     

Guangdong Metal Transaction Center has Become the Second Largest Precious Metal Transaction Platform Nationwide

正The reporter learned from Guangdong Province Precious Metal Transaction Center that in 2013the Center maintained healthy development momentum,and had become the second largest precious metal transaction platform in China in terms of market size;currently Guangdong is quickening steps of financial innovation for the Center,aiming to build a transaction center with international core competitiveness.