Impact of multiple FSP passes on structure, mechanical, tribological and corrosion behaviors of AA6061/316 stainless-steel reinforced Al matrix composites

Abstract

Stainless steel particulates were chosen as alternatives to ceramic particles to improve particle-matrix bonding, toughness, and performance of aluminum metal matrix composites. A multi-pass friction stir processing route was utilized for the development of AA6061/316 stainless steel reinforced composites by varying the number of tool passes (1–4). Detailed microstructure analysis, corrosion, hardness, wear, tensile, and impact toughness behaviors of the developed composites were studied. An increment in the number of tool passes (1–4) did not cause a particle-matrix reaction or alter the presence of inherent Mg2Si, Al, and ferrous phases in the composites. The progressive increment in the tool passes significantly enhanced the dislocation density, grain refinement, particle refinement (36.4–22.4 μm), and dispersion within the composite's structure due to the successive rotating tool-induced high straining and plastic deformation, dynamic recrystallization, and Zener pinning phenomena. The successive tool pass-induced microstructure improved the microhardness value (129–146 HV), tensile strength (163–241 MPa), impact toughness (5.7 ± 0.1–11.35 ± 0.1 J/cm3), and corrosion resistance of the composite while the wear rate (0.37–0.11 mm3/Nm) and the mean friction coefficient (0.37 ± 0.1–0.21 ± 0.1) of the composite were significantly reduced as the number of the tool passes was increased. The 4-pass friction stir processing technique is thus recommended for the development of AA6061/316 stainless steel reinforced composites.