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通过机械混合和低温球磨的方法制备了具备“双重纳米结构”特征的B_4C颗粒(~60 nm)增强纳米晶铝基复合材料的粉体。通过扫描电镜(SEM)、透射电镜(TEM)和高分辨透射电镜(HRTEM)等对Al/B_4C复合粉体的颗粒形貌、微观组织、B_4C颗粒在铝基体中的分散性、Al/B_4C界面结合情况等进行了观察表征和分析讨论。结果表明,随着球磨时间的增加,Al/B_4C复合粉体的颗粒形貌呈现出“近似球状→薄片状→圆饼状→不规则团聚体”的演化规律。这一现象除了与球磨过程中的“破碎-焊合”综合作用有关外,还与粉体中纳米B_4C颗粒的“搭桥”作用有关。Al/B_4C复合粉体经低温球磨2 h后,基体纯铝的晶粒基本呈等轴晶,并且大多数晶粒尺寸在200 nm以下。此外,纳米B_4C颗粒在铝基体中的分布比较均匀,且B_4C颗粒和铝基体的界面纯净无杂质,基本实现了冶金结合。
B_4C particles (~ 60 nm) reinforced nanocrystalline aluminum matrix composites with “double nanostructures” were prepared by mechanical mixing and low temperature ball milling. The morphology, microstructure, dispersibility of B_4C particles in aluminum matrix, the Al / B_4C interface and the properties of Al / B_4C composite powders were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM) Combined with the situation were observed and analyzed and discussed. The results show that with the increase of ball milling time, the morphology of Al / B_4C composite powders shows the evolution of “nearly spherical → flaky → round cake → irregular aggregates”. In addition to the phenomenon of “crushing - welding” in the ball milling process, this phenomenon is also related to the “bridging” effect of nano-B_4C particles in the powder. The Al / B 4 C composite powders were ball-milled for 2 h at low temperature, and the grains of the matrix pure Al were almost equiaxed and most of the grain sizes were below 200 nm. In addition, nano-B_4C particles distributed evenly in the aluminum matrix, and the interface of the B_4C particles and the aluminum matrix was pure and free from impurities, and the metallurgical bond was basically achieved.