Effect of multi-pass friction stir processing on the microstructure, mechanical and wear properties of AA5083/ZrO2 nanocomposites

In this study, multi-pass friction stir processing using zirconia nanoparticles was performed on AA5083 sheets to fabricate surface nanocomposites. Effect of using different number of passes on the microstructure, microhardness, tensile and wear properties of the specimens was investigated. Therefore, it was found that iteration of FSP consistently improves tensile properties and microhardness of the materials. This was mainly related to microstructural modification through FSP, including better dispersion of powders, finer grain size and minimum clustered particles. EBSD and TEM analysis indicated a large number of high angle grain boundaries and occurrence of continuous dynamic recrystallization (CDRX) in the 8-pass FSP'ed nanocomposite. Wear test also showed that wear rate of the further processed specimens was distinctly lower than their counterparts. Moreover, fracture surface of the eight-pass processed material revealed ductile fracture consisting mostly of dimples and voids, similar to the base material. (C) 2017 Elsevier B.V. All rights reserved.