TiC-TiB2复相陶瓷的自蔓延高温合成研究

以Ti、B和C粉末为原料,采用SHS/PHIP工艺制备了不同组份的TiC-TiB2复相陶瓷,通过试验研究了复相陶瓷的微观结构特征和力学性能.结果表明,SHS反应产物纯净,TiC-TiB2复相陶瓷中只有TiC和TiB2两相存在;随着TiB2含量的增加,复相陶瓷中TiC颗粒尺寸变小,而TiB2颗粒有异常长大现象;TiC-TiB2复相陶瓷的相对密度、硬度和横向断裂强度均随TiB2含量的增加呈先增后减趋势;当TiB2与TiC的重量比为60%时,该复相陶瓷的横向断裂强度和断裂韧度分别为576MPa和5.45MPa·m1/2,而相对密度达到99.4%.     

绝热温度对超重力场燃烧合成TiC-TiB2组织及性能的影响

通过在(Ti+B4C)体系中引入相应含量的(CrO3+Al)高能铝热剂,采用超重力场燃烧合成,在不同绝热温度下制备出具有不同含量Cr基合金相的TiC-TiB2复合陶瓷。XRD、FESEM和EDS分析表明,TiC-TiB2复合陶瓷主要由TiB2片晶与不规则的TiC晶粒组成,少量的Al2O3夹杂颗粒孤立地分布于陶瓷基体上,而Cr基合金相则分布于TiB2片晶与不规则TiC晶粒周围。增加燃烧合成绝热温度,因增加了陶瓷熔体中的Cr基合金相含量,不仅促进陶瓷致密化,而且促使陶瓷凝固组织细化,使得TiB2片晶诱发的裂纹偏转、裂纹桥接、片晶拔出及Cr基合金相所引起的延性相增韧随之增强,进而使陶瓷断裂韧度与抗弯强度增大。     

原位合成NiAl(FeAl)/TiB_2+Al_2O_3复合材料

Al2O3+TiB2复相陶瓷材料具有高硬度、高熔点、高导热、低膨胀系数、高耐磨性、高温化学稳定性等优良的性能,但由于两种材料都属于硬而脆的材料,复合后仍然存在脆性大、裂纹敏感性强、抗机械冲击性和温度急变形差等缺点.为了克服这些缺点,在陶瓷相中添加金属间化合物(NiAl或FeAl).X射线衍射结果表明,合成产物的主要组成相分别为Al2O3+TiB2、Al2O3+TiB2+NiAl及Al2O3+TiB2+FeAl,进行燃烧合成反应.通过对不同成分反应产物的相对密度、强度、断裂韧度对比,可知产物的相对密度在FeAl含量为15%时达到最高99.5%,Al2O3+TiB2+NiAl体系中在NiAl含量为20%时达到最高98.5%.随着金属间化合物含量的增加,合成复合材料的硬度下降,而断裂韧度提高.     

纳米/微米Al2O3-ZrO2内衬复相陶瓷的自蔓延高温合成

采用SHS重力分离技术制备出内衬Al2O3-ZrO2复相陶瓷.复相陶瓷基体主要由纤维状(Al2O3+ZrO2)共晶体组成,其中共晶体的ZrO2纤维直径达到纳米/微米尺度.经Vickers压痕法测试其断裂韧度为15.96MPa·m1/2,SEM观察和陶瓷材料断裂韧度测试得出裂纹的扩展主要受共晶体中Al2O3-ZrO2纳米/微米相增韧机制控制,迫使裂纹沿共晶体边界或层片共晶体Al2O3-ZrO2相界偏转,从而维持了该复相陶瓷较高的断裂韧度.     

超高重力场燃烧合成TiC-TiB_2的组织变质与断裂行为

采用超高重力场燃烧合成工艺,并从500 g到2 500 g每间隔500 g依次增大超重力场加速度,制备系列TiC-TiB2凝固陶瓷。经XRD、FESEM和EDS分析,发现陶瓷显微组织均由片晶的TiB2基体相、不规则的TiC第二相及少量的Al2O3夹杂与Cr基金属相组成。增大超重力场加速度,反应熔体内部各组份之间的对流(Stokes)加强,可加快Al2O3液滴的上浮与分离,促进TiC-TiB2-Me液相成分均匀化,使陶瓷显微组织得以细化,且当超重力场加速度超过2 000 g时,出现TiB2片晶厚度小于1μm的超细晶组织,同时随陶瓷基体上Al2O3夹杂量降低、TiB2片晶异常长大弱化,陶瓷组织均匀性提高。经FESEM断口形貌与裂纹扩展观察,发现TiB2基体相的裂纹桥接与拔出,并耦合晶间Cr基延性相增韧构成陶瓷的复合增韧机制,且随超重力场加速度增大,陶瓷的致密性与组织均质性得以提升,不仅促进TiB2基体相裂纹桥接与拔出,而且可增大Cr基延性对陶瓷增韧的贡献,使得陶瓷弯曲强度与断裂韧性分别同时达到最大值(975±16)MPa和(16.8±1.2)MPa·m1/2。     

制备复相结构陶瓷坯件的自反应喷射成形工艺研究

以Ti粉、B4C粉和蔗糖(C的前驱体)为原料,采用自反应喷射成形技术在石墨模具内制备了Ti(C,N)-TiB2复相结构陶瓷坯件,研究了自反应喷射成形技术中几个关键工艺参数如气粉质量流率比(G/C值)、喷射距离和喷射团聚粉预热温度对制备该复相陶瓷坯件的影响。研究表明,对喷射沉积坯件孔隙度影响由主到次的参数依次为G/C值、喷射距离和预热温度。正交试验结果得出,利用Ti-B4C-蔗糖体系制备Ti(C,N)-TiB2复相陶瓷坯件的最佳工艺条件是:G/C值为11、喷射距离为220mm,复合粉预热温度为210℃。所制备复相陶瓷坯件组织结构均匀、致密,主要由TiC0.3N0.7、TiB2与TiO2相及少量孔隙组成;其中TiC0.3N0.7和TiB2为主相,TiO2为副产物相;坯件孔隙度为2.9%,维氏硬度、抗弯强度和断裂韧度分别为17.3GPa、387MPa和6.0MPa.m1/2。     

烧结温度对制备多孔TiB_2-TiC复相陶瓷性能的影响

为了获得孔隙度为(30±5)%TiB2-TiC复相陶瓷,采用反应烧结法,在不同温度下进行真空烧结制备出多孔TiB2-TiC复相陶瓷.主要研究了烧结温度对样品的密度、透气性和力学性能的影响,并对反应过程中样品的相组成进行了分析.试验结果表明:反应过程于1 000℃开始,于1 300℃结束;反应过程中存在TiB、Ti3B4中间相,反应完成后最终产物只有TiB2和TiC两相.随着烧结温度的升高,样品的密度和抗弯强度均是逐渐增大的,最大孔径和相对透气系数则是逐步降低的.于1 700℃烧结制备出的复相陶瓷的密度为3.2g/cm3、开孔隙度为29.5%、抗弯强度达到了120MPa,达到了预期目标.     

Cr对超重力场燃烧合成TiC-TiB_2复合陶瓷凝固行为的影响

采用超重力场燃烧合成技术,以Ti+B4C为主反应体系,同时辅以不同含量的CrO3+Al增强体系,制备出不同Cr含量的TiC-TiB2复合陶瓷。XRD、FESEM与EDS分析表明,所得TiC-TiB2复合陶瓷主要由大量细小的TiB2片晶、TiC球晶构成,富Cr金属相多与TiB2片晶交织在一起。随着CrO3+Al含量增加,体系绝热温度升高,TiC-TiB2复合陶瓷中富Cr金属相体积分数逐渐增加。分析认为,超重力场下燃烧反应完成后,得到Ti-Cr-C-B合金液相,在冷却凝固过程中,TiC率先形核析出,TiB2随后析出,Cr及少量未反应Ti最后析出,并对TiB2片晶形成的骨架结构进行补缩,从而提高了TiC-TiB2复合陶瓷的致密性。     

原位自生TiB增强Ti-55531合金复合材料组织与力学性能研究

采用真空自耗电弧熔炼及近等温热塑性变形方法制备了原位自生TiB/Ti-55531复合材料。利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)及万能材料试验机等研究了增强相含量对其组织与力学性能的影响规律,并分析其失效断裂机制。结果表明,热处理态TiB/Ti-55531复合材料的组织特征为α相、TiB增强相弥散分布于β基体。随着TiB增强相的引入及含量增加,复合材料的基体晶粒明显细化,沿晶界分布的粗条状α相逐渐球化,抗拉强度、屈服强度、杨氏模量明显增加,延伸率有不同程度降低。2vol%TiB/Ti-55531复合材料的强塑性匹配较好,抗拉强度为1444.2 MPa,屈服强度为1421.4 MPa,杨氏模量为115.5 GPa,延伸率为9.2%。随着TiB增强相的引入及含量增加,拉伸试样断口的韧窝数量减少,深度变浅,断裂机制逐渐从韧性断裂向混合断裂转变。     

Al2O3含量对ZrO2/Al2O3陶瓷材料微观结构和力学性能的影响

以陶瓷纺织剪刀为应用目标。开发成功ZrO2／Al2O3复相陶瓷材料，并对其微观结构和力学性能进行了研究。结果表明。随着Al2O3含量的增加，材料晶粒逐渐减小，材料中t相ZrO2的含量呈上升趋势。这有利于材料断裂韧度和横向断裂强度的提高；当Al2O3含量（质量分数）为20％左右时，ZrCh／Al2O3复相陶瓷材料的综合力学性能最佳。     

China's Major Non-ferrous Metals Imports & Exports

正~~     

Zinc Production by Province in 2014

正~~     

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.     

Seven Rare Earth Projects Involving Close to 3 Billion Yuan Investment Landed In the HighTech Zone

正On May 22,Baotou Rare Earth Industry Cooperation Consultation MeetingProject Agreement-signing Ceremony was held in Ningbo,nearly 40 enterprises from Ningbo,Guangdong,Hunan,and Shanxi participated in project consultation.After multi-lateral communication,agreements were signed for a total of 7 rare earth projects successfully.