Synthesis of ex-situ Al5083 reinforced with mechanically-alloyed CNTs and Fe2O3 nanoparticles using friction stir processing

Abstract

Friction stir processing (FSP) was employed to synthesis ex-situ Al5083 nanocomposite reinforced with different mechanically-alloyed aluminium nanocomposites containing carbon nanotubes (CNTs) and ferric oxide (Fe 2 O 3 ). The mechanically-alloyed nanocomposite reinforcements were initially prepared using ball milling and introduced into the stir zone (SZ) of rolled Al5083 alloy during subsequent FSP. The FSPed nanocomposites were successfully processed with uniform dispersion of CNTs and Fe 2 O 3 nanoparticles resulting in the achievement of unique properties. Addition of nanocomposite reinforcements significantly reduces the grain size of FSPed nanocomposites. The least grain size belongs to hybrid FSP5 (Al/CNTs/Fe 2 O 3 ) nanocomposite with grain size of 6.9 ± 0.4 μm which is 7.4 and 2.6 times smaller than base metal (BM) and un-reinforced FSPed (FSP1). Microstructure of FSP5 nanocomposite contain largest fraction of high angle grain boundaries (HAGBs) of 87 %. Among all FSPed nanocomposites, hybrid FSP5 nanocomposite has the best mechanical properties in the terms of microhardness, Yield strength, ultimate tensile strength and wear resistance; with 1.6, 2.7, 3.5, 3.1 times, respectively, superior to BM. The significant improvement is attributed to the desirable microstructural changes including well dispersion of nanoparticles and extensive grain refinement. Hybrid FSP5 has an excellent magnetic and electrical resistivity when compared with the BM, however, its magnetic properties is slightly slower than FSP4 specimen due to de-magnetization effect of CNTs.