Semnan University Press Mechanics of Advanced Composite Structures 2423-4826 14 1 2027 04 01 Investigation of the Mechanical and Tribological Behaviour of Al Alloy and Al/ZrO2Ex-Situ Nano Composites 19 26 10399 10.22075/macs.2026.37138.1824 EN Bhavana Singh Department of Mechanical Engineering, SET IFTM UNIVERSITY, Moradabad, 244001, India 0000-0003-0917-4157 Vaibhav Trivedi Department of Mechanical Engineering, SET IFTM UNIVERSITY, Moradabad, 244001, India Ankur Goel Orthopedic, Sri sai super specialityHospital, Moradabad, 244001, India Journal Article 2025 03 20 The present study investigates the mechanical and tribological behaviour of Al alloys and Al/ZrO₂ ex-situ composites, focusing on their microstructural evolution and property enhancement. Al/ZrO₂ composites were synthesised using stir casting, incorporating 1, 3, and 5 wt.% ZrO₂ particles. Alloys and composites were characterizedusing X-ray diffraction (XRD), optical microscope (OM), and scanning electron microscopy (SEM)to analyse phase formation, particle distribution. Microstructural analysis revealed homogeneous dispersion of ZrO₂ particles, promoting load transfer and matrix strengthening. Mechanical properties were analysed using Vickers microhardness and uniaxial tensile tests, demonstrating substantial increases in hardness and tensile strength with increasing ZrO₂ content due to grain refinement, dislocation strengthening, and Orowan strengthening mechanisms. Tribological performance was evaluated using a pin-on-disc apparatus under varying loads (10N- 30N) and sliding speeds (1 m/sec -3 m/sec). The Al/ZrO₂ composites exhibited a significant reduction in the wear (up to 50%) compared to the unreinforced alloy, attributed to the load-bearing capacity of ZrO₂ particles and the formation of a protective tribolayer. Surface morphology of the worn samples, analysed using SEM, indicated a transition from abrasive to mild adhesive wear with the addition of ZrO₂. Further topographical parameters were studied using atomic force microscopy (AFM), which suggests a decrease in surface roughness from 0.87 µm to 0.70 µm at3wt. % of ZrO₂ compared to the base alloy. https://macs.semnan.ac.ir/article_10399_17b59308979f035f0da44a550b46dd8a.pdf