English abstract
Aluminum-based nanocomposites commonly offer superior properties that can
replace conventional steel alloys in many industries such as automotive, aerospace and
construction, aiming to reduce the weight and save energy. In this present study, aluminum
nanocomposites were successfully produced through stir-squeeze casting process with and
without the aid of ultrasound sonication (US). The matrix material was scrap automobile
aluminum alloy (A356). About 1% of SiC nanoparticles (15.3 g) with an average particle
size of 40 nm were used as a reinforcement material. For the purpose of comparison, A356
aluminum casts were also produced with and without US. The work commonly aimed to
develop a suitable aluminum nanocomposite that can withstand highly-wear environment
like brake disc and examine the effect of using ultrasonic sonication as an advanced
additional mixing technique in the mechanical and tribological properties of the produced
material. As a first step, the modified digital logic method (MDLM) was conducted to select
both matrix and reinforcement materials for the above-mentioned brake disc application.
The analysis of the produced material was conducted based on their microstructure,
porosity, hardness, tensile strength, compression strength and wear/tribological
performance. In the microstructure characterization, optical microscope, and scanning
electron microscope (SEM) were used, revealing different morphologies and grain structures
in the cast materials. Energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction
(XRD) were also performed to check the compositions and confirm the presence of SiC
nanoparticles in the aluminum matrix. The porosity was greater in the nanocomposite's
samples than that of pure matrix samples. This was attributed to the tendency of pore
formation when ceramic particles weren't properly distributed throughout the matrix, and
hence clusters and agglomerations of nanoparticles took place. That also explain, the
significant reduction in porosity when the ultrasonication was applied which helped to break
these clusters and agglomerations. In terms of mechanical properties, the A356+SiC sample
with US exhibited, the highest hardness with a value of 70.8 HRB, the highest tensile
strength (163.25 MPa), and the highest compressive strength (387.2 MPa). It also
demonstrated the lowest abrasive wear loss (0.0016 g) among the four produced casts. The
improvements of mechanical properties and wear resistance were attributed mainly to three
factors: Hall-Pitch effect, reduction in porosity, and uniform distribution of the
reinforcement particles in the aluminum matrix.
