Compressive, shear, and fracture behavior of CNT reinforced Al matrix composites manufactured by severe plastic deformation

Abstract

In this work, carbon nanotubes (CNTs) reinforced aluminum (Al) matrix composites are synthesized using Bc equal-channel angular extrusion (ECAP) route and their mechanical behavior is examined under compression and shear deformation. The results show that at room temperature, eight ECAP passes are necessary to achieve the density of the composite where the effect of CNTs in enhancing the mechanical properties become significant. Samples of pure Al are also processed under the same ECAP conditions, and their properties are further examined to facilitate the comparison. The well-densified composites with only 2 vol. % of CNTs exhibit an approximately 30% increase in yield strength compared to the pure Al samples. Microstructure data in terms of porosity volume fraction, crystallite size, and dislocation density, along with the residual lattice strain measurements, are used to explain the observed improvements in strength. As measured by X-ray diffraction (XRD), higher levels of dislocation density, smaller crystallite sizes, and larger residual lattice strains are present in Al-CNT than in pure Al samples. Finally, fractographic analysis using scanning electron microscopy is performed revealing that the fracture surfaces of the composite exhibit a more brittle behavior than pure Al samples.

Influence of CNTs decomposition during reactive friction‐stir processing of an Al–Mg alloy on the correlation between microstructural characteristics and microtextural components

“…The same phase transformations were also observed during hot‐pressing of carbon nanotubes in the Al‐matrix at temperatures higher than 793 K (Liu et al ., ). Also, failure of CNTs during other SPD techniques such as MA, ARB and ECAP at room temperature under the repetitive high shear strains have been reported (Salimi et al ., ; Zare et al ., ; Pérez‐Bustamante et al ., ), because CNTs are more fragile when combined axial and radial loading is applied (Shen & Zhang, ). For the present study, high magnification TEM images of Figures and from different regions at different magnifications show a striking change in the morphology of reinforcing phase.…”

“…Due to the high aspect ratio of CNTs, attaining a homogenous dispersion from these reinforcing materials is rather challenging (Carvalho et al, 2013;Khodabakhshi et al, 2017). Therefore, several methods have been introduced and implemented such as mechanical alloying (MA) (Wang et al, 2009), squeeze casting (SC) (Alhashmy et al, 2015), spread dispersion (SD) (Liao & Tan, 2011), accumulative roll bonding (ARB) (Yoo et al, 2012), equal channel angular pressing (ECAP) (Zare et al, 2016), spark plasma sintering (SPS) (Najimi & Shahverdi), high-pressure torsion (HPT) (Phuong et al, 2014) and friction-stir processing (FSP) (Lim et al, 2009). Among these, FSP as developed by Mishra et al (2003) based on the friction-stir welding (FSW) technology is a promising route for the purpose of surface modifications.…”

Solid-State Recycling of Light Metal Reinforced Inclusions by Equal Channel Angular Pressing: A Review

“…The process of was proposed that the consolidation was performed at room temperature. Furthermore, the tensile strength decreases by increasing the temperature of ECAP processing and the total elongation is also increased [17]. The researcher proposed that when the temperature is increased from 120°C to 180°C, it can cause decreases of mechanical properties while the precipitate and grain size are increased.…”

A Comparative Study on Microstructure and Mechanical Properties of A356-B4c and A356-Graphite Composites

“…The inadequacy of metals and alloys in providing both strength and stiffness to a structure has led to the development of various composites particularly metal matrix composites (MMCs) [1,2].…”