摘要:
采用草酸盐共沉淀法制备了YBa2Cu3O7 (YBCO)粉体, 利用真空热压烧结法制备了不同质量分数的YBCO/Cu复合材料, 测定了YBCO/Cu复合材料的密度、硬度和电导率, 利用MMU-5GA磨损试验机对YBCO/Cu复合材料进行了摩擦磨损试验。采用XRD、SEM和TEM对YBCO粉体及YBCO/Cu复合材料的微观结构、磨损表面形貌及物相组成进行了表征。研究了YBCO质量分数对YBCO/Cu复合材料组织及性能的影响。结果表明:所制备的YBCO粉体物相为Y123相, 其层状结构明显, 粉体纯度高、杂质少, 粒度达到纳米级;纳米YBCO可显著细化YBCO/Cu复合材料的基体组织, 提高复合材料的摩擦学性能。随着YBCO质量分数增加, 基体组织中纳米YBCO颗粒分布均匀度降低, 逐渐出现团聚;YBCO/Cu复合材料的电导率和密度降低, 硬度先升高后降低, 摩擦系数逐渐减小。3% YBCO/Cu复合材料的摩擦磨损性能最好。YBCO/Cu复合材料强化机制为Orowan强化、热错配强化和细晶强化;其磨损机制主要为塑变磨损、磨粒磨损和疲劳剥落。
Abstract:
YBa2Cu3O7 (YBCO) powder was prepared by oxalate co-precipitation method. YBCO/Cu composites with different mass fractions were prepared by vacuum hot-pressed sintering method. The density, hardness and conductivity of YBCO/Cu composites were measured. The friction and wear test was performed on YBCO/Cu composites by MMU-5GA abrasion equipment. The microstructure, wear surface morphology and phase composition of YBCO powder and YBCO/Cu composites were characterized by the means of XRD, SEM and TEM. The influence of YBCO mass fraction on microstructures and properties of YBCO/Cu composites were investigated. The results indicate that the YBCO powder phase is Y123 phase with apparent layer structure, and powders are nano-scale particles with high purity and less impurity. The matrix structures of YBCO/Cu composites are obviously refined and the tribological performance are improved by adding YBCO nano-particles. With the increase of YBCO mass fraction, the uniformity of YBCO nano-particles in matrix reduces and particles agglomerates gradually, the conductivity and density of YBCO/Cu composites decrease, the hardness firstly increases then decreases, the friction coefficient gradually reduces. The friction and wear performance of 3% YBCO/Cu composite are best. The strength mechanisms of YBCO/Cu composites are Orowan strengthening, thermal mismatch strengthening and grain refinement strengthening.The dominant wear mechanisms are plastic deformation wear, abrasive wear and fatigue flaking.
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