Microstructural, Mechanical and Strengthening Mechanisms of Al7075 Metal Matrix Composite with Al2O3 Nano Particle Processed Through Ultrasonic Cavitation Assisted Stir-casting

In this investigation, we produced Al7075 matrix composites using a stir casting method enhanced by ultra-sonic cavitation, reinforcing them with nano-Al2O3 particles. The SEM microstructural analysis confirmed the presence of nano-Al2O3 particles in all the composites, showcasing their consistent particle size and reasonably even distribution within the matrix. Optical microscopic examinations revealed that the presence of nano-Al2O3 particles, along with the aggressive ultrasonic cavitation effect, resulted in grain refinement in the matrix phase. As the quantity of nano-Al2O3 particles increased, the mechanical properties of the composites exhibited significant enhancement. Remarkably, even with only 2.0wt.% of nano-Al2O3 particle reinforcement, the manufactured composites exhibited an impressive yield strength of 134 MPa, representing a remarkable 93.3% improvement compared to the yield strength of the Al7075 matrix alloy treated solely with ultrasound. We assessed the strength of Al7075/Al(2)O(3)np composites using various models for strengthening mechanisms. Among these, the dominant contributor to strengthening was the thermal mismatch effect, followed by Orowan strengthening, the Hall-Petch mechanism, and the load transferring effect for Al7075/Al(2)O(3)np composites. The contributions from differences in coefficient of thermal expansion (CTE), interactions between dislocations in the matrix and reinforcement particles, grain refinement, and load transfer mechanisms exhibited a consistent increase with the increasing percentage of Al(2)O(3)np content within the composite.