Influence of nanostructured Al on the mechanical properties and sliding wear behavior of Al-MWCNT composites

Abstract

In the present investigation, aluminum-based nanocomposites using multiwalled carbon nanotubes (Al-MWCNTs) were developed using nanostructured Al as a matrix and MWCNTs as nanofillers through a powder metallurgy route. The effect of nanostructured Al on the microstructure, microhardness, and sliding wear behavior of Al-MWCNT composites was studied. The crystallite size of nanostructured Al via mechanical milling for 25 h was found to be 32 nm. The major challenge associated with the development of Al-MWCNT nanocomposites is the uniform dispersion of the CNTs in the Al matrix, which was addressed by incorporating nanostructured Al. A significant improvement in the relative density, microhardness, and wear resistance of the Al-MWCNT composites up to the addition of 2 wt% of the MWCNTs was observed compared with as-received Al and its composites. The hardness of an Al-2 wt% MWCNT composite developed using nanostructured Al was 800 MPa, which was five times higher than as-received Al (170 MPa). Hardness and wear resistance found to be inversely proportional to crystallite size and porosity. The significant incremental improvement in the mechanical and wear properties mainly originates from fine-grain strengthening effects and the homogenous distribution of MWCNTs in the Al matrix. The presence of well-dispersed CNTs while maintaining structural integrity and aluminum carbide (Al4C3) crystals in the Al matrix were observed. The wear mechanism of Al-MWCNT nanocomposites was studied in detail. The wear mechanism of nanostructured Al composites has not been discussed in the literature previously; thus, this is the first comparative study of micro-and nanostructured Al-based composites.