1. The document describes the preparation and characterization of an aluminium metal matrix composite reinforced with welding slag using stir casting technique. Composites with 5%, 7%, and 9% weight fractions of welding slag particles were produced. 2. Hardness testing found that the hardness increased with increasing weight fraction of welding slag reinforcement. The unreinforced Al6061 alloy had a hardness of 95 BHN while the composite with 9% welding slag particles achieved a hardness of 96.9 BHN. 3. The study demonstrated that welding slag particles can effectively improve the hardness of an aluminium metal matrix composite when incorporated using stir casting, indicating potential applications where increased strength is required.