Microstructural evolution and mechanical properties of friction stir processed ZrB2/6061Al nanocomposites

Abstract In the present work, homogeneously dispersed ZrB 2 nanoparticles and fine-grained structures were successfully achieved by friction stir processing (FSP) of in situ 0–2 vol% ZrB 2 /6061Al nanocomposites. The effects of ZrB 2 additions on the microstructures and tensile properties were investigated. A combination of EBSD and TEM analyses revealed that ZrB 2 nanoparticles strongly suppressed (sub)grain boundary migration and/or orientation, and thus led to a continuous decrease in grain size, HAGBs fraction as well as B/ B ¯ shear texture intensity at higher ZrB 2 content. Moreover, compared with the processed 6061Al alloy, microhardness, strengths and elongation of the FSPed composites were significantly improved mainly due to the refined grains and ZrB 2 nanodispersoids. Quantitative calculation indicated that as ZrB 2 content increased, Orowan strengthening instead of grain refinement strengthening contributed the most to the yield strength.