Microstructure and wear characterization of carbon nanotubes (CNTs) reinforced aluminum matrix nanocomposites manufactured using selective laser melting

Abstract

Aluminum matrix composites are attractive in aerospace and automobile industry due to its low density, high strength and high corrosion resistance. Additive manufacturing methods such as selective laser melting enable the fabrication of such composites with a complex geometry, and the processing of novel, customized, tailored hybrid materials with unique hierarchical microstructures across multiple length scales. However, the microstructure evolution, wear resistance, frictional behavior under different fabrication and operation conditions of such composites still need to be explored. This study aims to fill the research gap in microstructure evolution and wear characterization of SLM-produced CNTs reinforced aluminum matrix nanocomposites. The surface characteristics, density, wear groove morphology, and surface damages in wear tests were examined. It was determined with SEM/EDS that the major phases of SLM-processed CNTs/Al-based nanocomposites were Al9Si and Si. These phases formed during the SLM process within the composites changed their wear behavior drastically. The wear surfaces were undergoing severe plastic deformation and progressive pitting. The wear rate of CNTs/AlSi10Mg nanocomposites specimens is about 33% lower than that of AlSi10Mg specimens. The higher wear resistance of the CNTs/AlSi10Mg nanocomposites specimens with shallow and narrow wear groove is attributed to the CNTs reinforcement induced higher surface hardness and also the unique hierarchical microstructure of the nanocomposites. The results showed that the SLM-produced CNTs reinforced aluminum matrix nanocomposites have good potentials to be an alternative to pure AlSi10Mg counterparts in terms of hardness, strength, frictional and wear behavior.