NiFe2O4基金属陶瓷的电导率

制备了铝电解用NiFe2O4基金属陶瓷惰性阳极,研究了环境温度及材料成分对电导率的影响.实验结果表明NiFe2O4基金属陶瓷的电导率主要受温度、陶瓷基体电导率、金属成分及金属相在陶瓷相中分散度的影响;当温度从573 K升至1 233 K时,NiFe2O4陶瓷的电导率由0.099 S/cm提高到2.105 S/em;与NiFe2O4陶瓷相比,金属陶瓷的电导率有极大的提高,但二者随温度的变化趋势是一致的;1 233 K时,金属含量为5%Ni,5%Cu和4.25%Cu+0.75%Ni的NiFe2O4基金属陶瓷的电导率分别为20.576 S/cm,14.970 S/cm和18.797 S/cm,用作铝电解惰性阳极已能满足要求,但与当前铝电解碳素阳极材料相比还存在很大距离.     

TaC含量对TiCN基金属陶瓷组织与性能的影响

以TiC,TiN,WC,Mo,Co,Ni和Ta C为原料制备TiCN基金属陶瓷,结合XRD,SEMEDS和力学性能测试,研究TaC含量对TiCN基金属陶瓷物相组成、显微组织与力学性能的影响。结果表明:TiCN基金属陶瓷的硬质相为TiC_(0.7)N_(0.3),Mo C,TiWC_2和TiTaCN。粘结相Co,Ni固溶Ti,W,Mo,Ta元素形成Ti_(0.08)Ni_(0.92),TiCo_3,W_(0.15)Ni_(0.85),Co_(0.9)W_(0.1),Ta_(0.08)Ni_(0.92)和Mo_(0.09)Ni_(0.91)等。TiCN基金属陶瓷的显微组织由黑色相Ti(C,N)、灰色相(Ti,Mo,Ta,W)(C,N)和白色相(Ti,Mo,Ta,W)C-Co-Ni组成,形成黑芯-灰环及黑芯-白环-灰环包覆结构。随TaC含量增加,固溶相(Ti,Ta,W,Mo)(C,N)的含量与黑芯-白环-灰环包覆结构相增加,TiCN基金属陶瓷的抗弯强度提高,硬度略有下降。适宜的TaC添加量为9%,所得金属陶瓷的抗弯强度和硬度HV分别为1 299 MPa和1 252 MPa。     

Preparation and properties of VC + Ni cermets with controlled carbon-to-metal ratio

A series of VC + Ni cermets was prepared where the carbon to metal (C / M) ratio of the carbide was varied from 0.86 to 0.75. Transmission electron microscopy and diffraction were used to determine the C/M ratio of the carbide and binder microstructure. At high C/M ratios, the carbide was principally V₈C₇ or V₈C₇ + V₆C₅, while at low C/M ratios the carbide was V₆C₅ or V₆C₅ + V₄C₃. The vanadium content of the binder increases as the C/M ratio of the carbide is decreased. The mechanical behavior of the cermets was evaluated by crack resistance and hardness measurements. In inverse crack resistancevs hardness plots, the VC + Ni cermets exhibit three types of behavior (labeled Type I, II, and III) in order of decreasing fracture toughness for a given hardness. Auger electron spectroscopy and scanning electron microscopy show that the three behavior types are characterized by differences in the dominant fracture mode. The fracture mode is principally transgranular fracture through the binder for Type I, transgranular cleavage of carbides for Type III, and intergranular or mixed fracture mode for Type II. The differences in fracture mode and mechanical behavior are induced by changes in microstructural features, as well as changes in the binder composition and formation of second phases. These results suggest that binder strengthening is a viable means to improving cermet performance only in systems when the cleavage energy of the carbide is sufficiently high to withstand the stresses generated by plastic flow in the binder. Formerly with Martin Marietta Laboratories, Baltimore     

Influence of sintering conditions on some properties of metal-aluminum oxide cermets

Summary A study was made of the sintering and properties of materials in the system corundum-metal. It was confirmed that the density of these cermets is influenced by the difference between the sintering temperatures of their oxide and metal constituents. The addition of MgO to the Al₂0₃ was found to have a beneficial effect on sintering in the system corundum-tungsten (molybdenum).Translated from Poroshkovaya Metallurgiya, No. 6 (66), pp. 34–40, June, 1968.     

Effect of annealing on the structure and properties of hot-pressed boron carbide base cermets

Conclusions During the annealing of a hot-pressed boron carbide-aluminum materials at a temperature exceeding the melting point of aluminum intense formation of-AlB₁₂ takes place. This has a deleterious effect on the strength properties (transverse rupture strength _tr, fracture toughness k_Ic, and impact strengtha) of the material and increases its hardness and electrical resistivity. It follows therefore that, to obtain boron car-bide-aluminum materials of maximum strength, it is necessary to perform their liquid-phase pressing under high pressures (above 0.5 GPa) and dispense with subsequent annealing. Annealing at a temperature below the melting point of aluminum brings about only very small changes in the structure of the material, and the resultant fall in hardness is less than the increase in hardness. Consequently, when it is necessary to increase the hardness of the material and a slight loss of strength is acceptable, recourse may be had to low-temperature annealing (below 660°C).Translated from Poroshkovaya Metallurgiya, No. 9(273), pp. 51–54, September, 1985.     

亚微米级Ti(C,N)基金属陶瓷的显微组织和力学性能

以亚微米级的粉末为原料制备Ti（C,N）基金属陶瓷,通过透射电镜（TEM）、扫描电镜（SEM）、能谱分析（EDX）等方法研究其在烧结过程中的组织结构变化规律及特点,并探讨烧结工艺参数对金属陶瓷力学性能的影响。结果表明,随着烧结温度升高,Ti（C,N）基金属陶瓷的组织更均匀,硬质颗粒逐渐球化,表面的Rim相更完整。Rim相分为两层,里层Rim相的Mo、W含量比外层Rim相高,里层Rim相是在固相烧结阶段形成的,外层Rim相是在液相烧结阶段形成的。Rim相的形成及晶粒长大都是通过溶解-析出机制进行的。在1 410℃下保温60 min,可获得较佳的力学性能,抗弯强度达2 266 MPa,硬度为HRA 90.6。     

Phase evolution,microstructure and properties of Y2O3-doped TiCN-based cermets

Y2O3-doped TiCN-based cermets were prepared by pressureless sintering with powders TiC, TiN, Ni, etc. as main starting materials. The influence of sintering processes and Y2O3on properties of TiCN-base...     

合金元素对Mo2FeB2基金属陶瓷组织及性能的影响

采用反应烧结法制备了Mo2FeB2基金属陶瓷,研究了添加石墨、Cr和Ni等合金元素对金属陶瓷显微组织及性能的影响.结果表明:不同合金元素的添加对复合材料的微观结构的改变不尽相同,但由于细化晶粒或粘结相强度变化等因素,金属陶瓷的硬度及抗弯强度均能得到不同程度的提高;合金元素的添加能有效改善Mo2FeB2的摩擦磨损性能,其中添加石墨的复合材料因为晶粒拔出最小从而具有最优的摩擦学性能.