الفهرس 
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Abstract
This research aimed to study the effect of adding CuO (2 wt.%) nanoparticles and changing the cooling rate, on the microstructure and mechanical properties of Al-2 wt.% Si.
The addition of CuO nanoparticles to Al-2wt.% Si (alloy A) resulted in a composite alloy (alloy B). We used optical microscopy (OM), scanning electron microscopy (SEM) connected to an energy dispersive spectrometer (EDS), X-ray diffraction (XRD), and positron annihilation Doppler broadening spectroscopy (PADBS) to study microstructure of alloys.
We used Vickers hardness tests and tensile tests to investigate the mechanical properties of the tested alloys. We cooled G1 samples in the air to " ~ "300 K and quenched G2 samples in iced water 0 oC (273 K) for both the alloy and composite.
The results showed increasing the strain rate from 0.004 to
0.04 min-1 or decreasing the temperature from 503 to 423 K could increase the hardening parameters, yield stress (σy), ultimate strength (σM), and Young’s modulus (Y) of all samples. Also, HV decreased as the aging temperature increased from 423 to 503 K.
Adding nanosized CuO or cooling samples in iced water resulted in smaller grains. Furthermore, alloy B exhibited the formation of intermetallic compounds (IMCs) CuAl2 and Cu3Si. The XRD data indicated the formation of phases in both alloys at 423, 463, and 503 K. In addition, we calculated the
dislocation density, lattice strain, and average crystallite size.
It can be seen from the activation energies and stress exponents that dislocation climbs through core diffusion as a control mechanism for both alloys.
For all examined samples, we observed a significant positive relationship between the value (HV) and PADBS parameters. The investigation showed that nanosized CuO and a rapid cooling rate increased composite specimen hardness. This finding is of great scientific significance, as aluminum and its alloys play a crucial role in various technical applications.