Microstructural evolution and mechanical property of nanoparticles reinforced Al matrix composites during accumulative orthogonal extrusion process

In this work, microstructures of nanoparticles reinforced Al matrix composites after each accumulative orthogonal extrusion process (AOEP) pass, were characterized by scanning electron microscopy, electron backscatter diffraction and neutron diffraction techniques. The results showed that the nanoparticle clusters were completely invisible and the initial fibrous grain morphology in the Al matrix was replaced by ribbon-like and equiaxed ones after 2 passes. No change of the grain structure after 3 passes is related to the occurrences of grain boundary sliding and the saturation of particles stimulated nucleation effect. In addition, the strong beta-fiber textures in the hot extruded composites (AOEP 1P) have been broken down after 2 passes of AOEP, leading to a lower texture fraction in the composites. As a result, a good combination of strength and ductility is achieved in the AOEPed composites. The mechanical anisotropy of composites is also diminished, attributed to the uniform particle distribution, homogeneous grain structures and low texture fractions.