摘要
Al−2CNTs−xAl2O3 nanocomposites were manufactured by a hybrid powder metallurgy and microwave sintering process.The correlation between process-induced microstructural features and the material properties including physical and mechanical properties as well as ultrasonic parameters was measured.It was found that physical properties including densification and physical dimensional changes were closely associated with the morphology and particle size of nanocomposite powders.The maximum density was obtained by extensive particle refinement at milling time longer than 8 h and Al2O3 content of 10 wt.%.Mechanical properties were controlled by Al2O3 content,dispersion of nano reinforcements and grain size.The optimum hardness and strength properties were achieved through incorporation of 10 wt.%Al2O3 and homogenous dispersion of CNTs and Al2O3 nanoparticles(NPs)at 12 h of milling which resulted in the formation of high density of dislocations and extensive grain size refinement.Also both longitudinal and shear velocities and attenuation increase linearly by increasing Al2O3 content and milling time.The variation of ultrasonic velocity and attenuation was attributed to the degree of dispersion of CNTs and Al2O3 and also less inter-particle spacing in the matrix.The larger Al2O3 content and more homogenous dispersion of CNTs and Al2O3 NPs at longer milling time exerted higher velocity and attenuation of ultrasonic wave.
采用粉末冶金和微波烧结工艺制备Al−2CNTs−xAl2O3纳米复合材料。研究工艺引起的显微组织特征与材料的物理、力学性能以及超声参数之间的相互关系。研究发现,复合材料的致密化和尺寸变化等物理性能与纳米复合粉体的形貌和粒径密切相关。当Al2O3含量为10%(质量分数)、球磨时间大于8 h、颗粒被大量细化时,材料的密度最大。Al2O3含量、纳米强化相的分布和晶粒尺寸对材料的力学性能有显著影响,当Al2O3含量为10%(质量分数)、Al2O3纳米颗粒球磨时间为12 h、碳纳米管均匀分布时,可形成高密度位错和大量晶粒细化,从而获得最佳的硬度和强度。同时,纵波和横波速度及衰减随着Al2O3含量和球磨时间的增加而线性增加。超声速度和衰减的变化取决于碳纳米管和Al2O3在基体中分布的均匀程度及其较小的颗粒间距。经过较长的球磨时间,Al2O3含量越高,碳纳米管和Al2O3分布越均匀,超声波的速度和衰减越大。
