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

Abstract

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.

A Systematic Review on the Mechanical, Tribological, and Corrosion Properties of Al 7075 Metal Matrix Composites Fabricated through Stir Casting Process

“…After 8 hrs of ball milling, hardness was increased by 160%, and after 2 hrs of milling, density increased by 99.96% from the base composite. Tis result ensures that the employed PM method efectively produces MMCs with enhanced mechanical properties [33].…”

Performance evaluation of AlTiN coated carbide tools during machining of ceramic reinforced Cu-based hybrid composites under cryogenic, pure-minimum quantity lubrication and dry regimes

“…This situation can be attributed to the irregularities such as encountered cutting tool and hard particles, fine to large voids in the structure, incoherent interfaces between soft matrix and hard reinforcement or other metallurgical defects. 10 Yellow lines show interrupted feed marks created on the surface during dry milling. According to images, these interrupted feed marks are clearly visible in dry medium while these tracks gradually reorganized with smoother traces under lubrication and cooling strategies.…”

“…7,8 By this way, dramatic changes have been achieved by optimizing the material types or selecting proper powder metallurgy parameters and solid/liquid phase production methods which directly affect interfacial bonding, structural integrity and accompanying final product’s overall performance. 9,10 The main point prohibiting the extensive utilization of hybrid composites is the their poor machining performance resulting from the dissimilar behavior of hard ceramic reinforcement and the ductile matrix phases. 11 To achieve desired dimensional accuracy in the end product and to boost machining performance, various researchers have examined the influence of different machining parameters or diverse hard tool(s) tips on the surface processing operations regulating final product characteristics.…”

Structural evolution of mechanically alloyed ODS steel powders during ball milling and subsequent annealing treatment

“…This observation perfected the particle shape image of illustrated in Figure 4, where flakes of 800 nm thickness were detected in 8h milled 9Cr-ODS powders. The detected texture formation was ascribed to the plastic deformation provoked by the thinned flake particles from the rolling effect of rigid milling medium [35]. Increasing milling time up to 16h resulted in vanishing of texture formation on the particles.…”