Influence of reinforcement incorporation approach on mechanical and tribological properties of AA6061- CNT nanocomposite fabricated via FSP

Abstract

• Multiple micro sized channels are used for reinforcement filling during FSP. • As compared to conventional FSP method, 23 % higher grain refinement is observed. • Tensile strength increased by 22 % at the cost of only 3% decrease in elongation. • Stable friction coefficient and 20 % reduction in specific wear rate. • Squeezed-out CNTs formed an effective tribolayer to prevent metal to metal contact. The present study aims to investigate the effect of reinforcement incorporation approach on the microstructure, mechanical, and tribological properties of the Al-CNT nanocomposite fabricated through friction stir processing (FSP). With the proposed multiple micro-sized channel reinforcement filling (MCRF) approach, the extensive grain refinement of ∼ 23 % is achieved as compared to the conventional single macro-sized channel reinforcement filling (SCRF) approach. The extensive grain refinement is attributed to the better consolidation obtained by the sandwiched aluminium matrix between the successive reinforcement grooves. The tensile strength of the MCRF fabricated composite is increased by ∼ 22 % at the cost of only ∼ 3% decrease in the elongation as compared to the un-reinforced processed alloy (Reference material, RM). The specific wear rate of MCRF fabricated Al-CNT composites is also reduced by ∼ 20 % as compared to RM. The improved wear performance is attributed to the formation of a carbon rich tribo layer which prevents the direct contact of composite with the counter surface. Whereas, the strengthening of Al-CNT composites is attributed to various mechanisms such as grain refinement, Orowan looping, load transfer through the interface and thermal mismatch between CNTs and Al matrix.