Nanocomposites of Al-Al₂O₃ are fabricated by means of friction stir processing (FSP). Effects of pin diameter and number of FSP cycles on tensile properties of the nanocomposites are investigated and the variations are correlated to the evolution of microstructure and distribution of nanoparticles in addition to agglomeration of Al₂O₃ nanoparticles. Investigation of agglomeration has been considered as an indirect indication for efficiency of the process for distribution of nanoparticles. The ductility of the nanocomposite is found to improve due to grain refinement during FSP. However, the ductility is likely to degrade if Al₂O₃ particles agglomerate and form coarse particles. The composite fabricated using the 6-mm pin indicates the maximum ductility which is attributed to formation of fine grain structure and efficient distribution of nanoparticles in the composite. Although, the grain structure in the composite fabricated using 8-mm pin is well refined, this sample shows significantly lower ductility with respect to the other samples. This was attributed to formation of coarse agglomerated particles. The second pass of FSP is found to slightly improve ductility and strength in composites fabricated using 4- and 6-mm pins but enforce significant improvements in the one with 8-mm pin. This is indeed because the second pass results in significant change in the distribution of nanoparticles or agglomerated particles in the latter case and negligible in the former ones. Grain structure and nanoparticle distribution and agglomeration can all affect the fracture surface of the tensile specimens of the fabricated nanocomposite to be ductile or brittle.

Al-Al ₂ O _3的纳米复合材料是通过摩擦搅拌工艺（FSP）制造的。研究了销钉直径和FSP循环次数对纳米复合材料拉伸性能的影响，这些变化与Al ₂ O ₃纳米颗粒的团聚以及纳米颗粒的微观结构和分布的演变有关。团聚研究被认为是纳米颗粒分布过程效率的间接指标。发现纳米复合材料的延展性由于FSP期间的晶粒细化而提高。但是，如果Al ₂ O ₃，延展性可能降低。颗粒聚结并形成粗颗粒。使用6毫米销钉制造的复合材料显示出最大的延展性，这归因于细晶粒结构的形成和纳米颗粒在复合材料中的有效分布。尽管使用8毫米销钉制造的复合材料中的晶粒结构得到了很好的细化，但该样品的延展性明显低于其他样品。这归因于粗糙的团聚颗粒的形成。已发现FSP的第二次通过可稍微提高使用4毫米和6毫米销钉制造的复合材料的延展性和强度，但对使用8毫米销钉的复合材料则进行了重大改进。实际上，这是因为第二遍导致在后一种情况下纳米颗粒或附聚颗粒的分布发生了显着变化，而在前一种情况下可以忽略不计。