Dispersion mechanism-induced variations in microstructural and mechanical behavior of CNT-reinforced aluminum nanocomposites

• Published in: Archives of Civil and Mechanical Engineering Vol. 22; no. 1; p. 55
• Main Authors: Doğan, Kemal, Özgün, Muhammed İhsan, Sübütay, Halit, Salur, Emin, Eker, Yasin, Kuntoğlu, Mustafa, Aslan, Abdullah, Gupta, Munish Kumar, Acarer, Mustafa
• Format: Journal Article
• Language: English
• Published: London Springer London 24.01.2022; Springer Nature B.V
• Subjects: Alloys; Aluminum; Aluminum base alloys; Aluminum matrix composites; Ball milling; Brinell hardness; Civil Engineering; Crystallography; Engineering; Grain boundaries; Grain refinement; High resolution electron microscopy; Hot pressing; Interfacial bonding; Mechanical Engineering; Mechanical properties; Morphology; Multi wall carbon nanotubes; Nanocomposites; Nanoparticles; Optical microscopes; Optical properties; Original Article; Orowan loops; Particle size; Powder metallurgy; Process controls; Raman spectroscopy; Scanning electron microscopy; Sintering (powder metallurgy); Specific gravity; Spray forming; Structural analysis; Structural Materials; Carbon nanotubes; Ball milling; Hot pressing; Microstructural characterization; Aluminum
• ISSN: 2083-3318; 1644-9665; 2083-3318
• DOI: 10.1007/s43452-022-00374-z

The combination of powder metallurgy and ball milling method has been widely regarded as the most beneficial route for producing multi-walled carbon nanotubes (MWCNTs)-reinforced aluminum matrix composites. In this study, the effects of different milling times (1, 2, 4, and 8 h) on the structural, morphological, and crystallographic properties of MWCNTs-reinforced Al7075 composite powders were characterized by particle size analyzer, Raman spectroscopy, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), and X-ray diffraction (XRD). After the morphological and structural characterization of the milled powders, the microstructural and mechanical properties of the hot-pressed composites were evaluated using an optical microscope, SEM, density, and Brinell hardness measurements. Considering milled powder characterization, the MWCNTs were gradually distributed and embedded within the matrix as the milling time increased. Milling for 8 h resulted in a minimum level of particle size (11 µm) with shortened and uniformly dispersed CNTs. Brinell hardness of the composite increased from 91 to 237 HB -a ⁓%160 after 8 h of milling. Such a remarkable increment in hardness could be attributed to several concurrent strengthening effects related to dispersion, solution, grain refinement, and Orowan looping mechanisms. However, relative density results revealed that the composite produced by 2 h milled powders exhibited the highest density (%99.96). The observed differences between hardness and density results were ascribed to powders’ deteriorated packing and sintering behavior due to an increment in the hardness of particles and variation in particle size range and morphology, which resulted from following different milling protocols.