第二相粒度对AgSnO_(2)触头材料润湿性和电接触性能的影响

选用TiO_(2)作为触头材料的添加剂,采用粉末冶金法制备了6种不同第二相(SnO_(2))粒度的AgSnO;和AgSnO_(2)/TiO_(2)触头材料。研究了2种触头材料的润湿性和电接触性能。用座滴法测量了Ag与SnO;之间的润湿角,并表征了材料的湿润性,使用JF04C电接触触头材料测试系统对材料电接触性能进行了测试,分析了不同第二相粒度的触头材料的润湿性和电接触性能的变化规律。结果表明,当第二相粒度为100~300 nm时,2种触头材料的性能均优于其它粒度的触头材料。

Effects of rare earth Ce addition on microstructure and mechanical properties of impure copper containing Pb

The effects of rare earth Ce on the microstructure and mechanical properties of impure copper containing Pb were investigated using OM,SEM,EPMA,TEM and tensile testing.TEM and EDS analysis reveal that spherical CePb3 particles form after Ce addition.CePb3 particles,with average size of^3.6μm,homogenously distribute in the Cu matrix.Due to small lattice misfit(~4.62%)with Cu matrix,CePb3 particles can act as effective nucleation sites beneficial to the grain refinement.Pb at grain boundaries seriously deteriorates the mechanical properties of Cu.The tensile strength and the elongation of Cu-0.1 Pb are decreased by 43.1%and 56.7%compared with those of pure copper,respectively.Ce can purify grain boundaries,cause the precipitation of CePb3 particles and refine grain sizes,which contribute to significant improvement of the mechanical properties of Cu.Compared with Cu-0.1Pb,the tensile strength(179 MPa)and the elongation(38.5%)of Cu-0.1Pb-0.3Ce are increased by 117.6%and 151.6%,respectively.

Influence of impurities on damping properties of ZK60 magnesium alloy

The influence of impurities on damping capacities of ZK60 magnesium alloys in the as-cast,as-extruded and T4-treated states was investigated by dynamically mechanical analyzer at room temperature.Granato and Lucke dislocation pinning model was employed to explain damping properties of the alloys.It is found that reducing impurity content can decrease the amount of second-phase particles,increase grain size and improve damping capacity of the as-cast alloy slightly.The as-extruded alloy with lower impurity content is found to possess obviously higher damping capacity in the relatively high strain region than that with higher impurity concentration,which appears to originate mainly from different dislocation characteristics.The variation tendency of damping property with change of impurity content after solution-treatment is also similar to that in the as-extruded and as-cast states. Meanwhile,the purification of the alloy results in an evident improvement in tensile yield strength in the as-extruded state.

基于模糊综合评判的稀土La掺杂AgSnO2触头材料性能评估

为了对掺杂稀土元素La的AgSnO2触头材料性能进行定量化分析,更准确的反应触头材料工作性能,将模糊综合评判应用于触头材料性能评估。采用改进层次分析法(AHP)将主观定性结论定量化,得到主观专家权重,通过客观数据信息得到客观熵权,用拉格朗日乘子优化法对两种权重进行综合权重计算,这样可以充分减少权重计算的主观性,发掘原始数据中所包含的信息量,使各指标权重的确定更加精确。综合评估第二相SnO2粒度对AgSnO2/La2O3触头材料物理和电接触性能的影响,案例分析结果验证了所提方法的有效性和实用性。最后进行物理与电接触性能实验,实验结果与综合评估结果相吻合,进一步验证了该评估方法的可靠性,为今后AgSnO2触头材料的应用提供科学的参考依据与方法。

Enhanced mechanical properties in oxide-dispersion-strengthened alloys achieved via interface segregation of cation dopants

With significantly enhanced irradiation resistance,high-temperature strength,and creep resistance,oxide-dispersion-strengthened tungsten(ODS-W)alloys present tremendous potential for high-temperature applications.However,the oxide particles tend to segregate at W grain boundary and grow up(even to micron),greatly suppressing their strengthening effect.It is always a great challenge to effectively refine and disperse the oxide particles at W grain boundary.Here,we successfully developed a new type of cation-doped W-Y2O3 alloy via a wet chemical method and subsequent low-temperature sintering.It was found that proper cation doping could not only significantly refine the intergranular Y2O3 second phase particles but also dramatically improve the sinterability of W matrix.These doping effects,as a result,simultaneously enhance the strength and ductility of the W-Y2O3 alloy.It was confirmed that the segregation of cation dopants at the W/Y2O3 interface is the origin of these doping effects.Furthermore,X-ray photoemission spectra(XPS)analyses confirmed that cation dopant segregation also obviously affects the chemical bonding(i.e.,W–O bond)along the W/Y2O3 interface.As a result,the ratelimiting mechanism for W grain growth is influenced remarkably,explaining well the difference of W grain size in various cation-doped W-Y2O3 alloys.For the refinement of intergranular Y2O3 particles,it can be understood well from both thermodynamic and kinetic views.Detailedly,W/Y2O3 interfacial energy and atom mobility for Y2O3 coarsening are all limited by cation dopant segregation.More importantly,this cation-doping approach can also be applicable to other ODS alloys for enhancing their comprehensive mechanical properties.