Abstract
The 2024 nanocomposite reinforced with Al2O3 nanoparticles was fabricated by the ultrasonic assisted semisolid stirring (UASS) method and rheoformed into a cylinder component. Microstructure, mechanical properties, and wear behavior of the rheoformed composite components were investigated. The results showed that the composite components with complete filling status and a good surface were rheoformed successfully. The deformation of semisolid slurries was mainly dominated by flow of liquid incorporating solid grains (FLS), sliding between solid grains (SSG), and plastic deformation of solid grains (PDS). Mechanical properties of the rheoformed composite components were influenced by stirring temperature, stirring time, and volume fraction of Al2O3 nanoparticles. The optimal ultimate tensile strength (UTS) of 358 MPa and YS of 245 MPa were obtained at the bottom of the rheoformed composite components after a 25-min stirring of composite semisolid slurry with 5% Al2O3 nanoparticles at 620 °C. Enhancement of mechanical properties was attributed to high density dislocations and dislocation tangles and uniform dispersed Al2O3 nanoparticles in the aluminum matrix. Natural ageing led to the occurrence of needle-like Al2CuMg phase and short-rod-like Al2Cu phase. UTS of 417 MPa and YS of 328 MPa of the rheoformed composite components were achieved after T6 heat treatment. Improvement of mechanical properties is due to the more precipitated needle-like Al2CuMg phase and short-rod-like Al2Cu phase. Wear resistance of the rheoformed composite components was higher than that of the rheoformed matrix component. Wear resistance of the rheoformed composite component increased with an increase in Al2O3 nanoparticles from 1% to 7%. A slight decrease in wear rate resulted from 10% Al2O3 nanoparticles due to greater agglomeration of Al2O3 nanoparticles. A combination mechanism of adhesion and delamination was determined according to worn surface morphology.
Highlights
Metal matrix composites (MMC) have exhibited some obvious advantages such as high specific strength, high specific stiffness, and good wear resistance [1,2,3]
The present investigation will deal with microstructure and mechanical properties of 2024 aluminum matrix composite reinforced with Al2 O3 nanoparticles
Α-Al2 O3 nanoparticles with an average size of 60 nm parceled by pure aluminum foil were added into the melt after 2024 aluminum alloy was melted at 670 ◦ C and held for 20 min
Summary
Metal matrix composites (MMC) have exhibited some obvious advantages such as high specific strength, high specific stiffness, and good wear resistance [1,2,3]. Aluminum matrix composites reinforced with nano-sized ceramic particles (AMCNCP) have attracted researchers’ attention because of higher strength, increased dimensional stability, high thermal stability, high modulus, and good wear resistance as compared to conventional materials [20]. Sajjadi et al [23] investigated the fabrication and mechanical properties of A356 composite reinforced with micro and nano-sized Al2 O3 particles by a developed compocasting method. Some novel methods were developed to realize uniform dispersion of nano-sized ceramic particles such as Al2 O3 and SiC. Acoustic streaming and cavitation created by ultrasonic wave led to a uniform dispersion of nano-sized SiC particles in molten A356 aluminum alloy [26,27]. Semisolid stirring and ultrasonic wave were joined together to obtain a uniform dispersion of nano-sized SiC particles in 7075 aluminum matrix. The present investigation will deal with microstructure and mechanical properties of 2024 aluminum matrix composite reinforced with Al2 O3 nanoparticles
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