Analysis of the Effect of Annealing Heat Treatment on the Mechanical Properties of Aluminium Alloy 6061

This study investigates the effect of annealing temperature on the mechanical properties and microstructural characteristics of aluminium alloy 6061. The research used a quantitative laboratory experimental approach with annealing temperatures of 450°C, 495°C, and 550°C. The specimens were held for 1 h at each temperature and then cooled slowly inside the furnace. Tensile testing was conducted using a Universal Testing Machine, hardness was evaluated using the Vickers method, and microstructure was observed using a metallographic microscope at 100× and 200× magnification. Three specimens were used for each temperature. The average tensile strength decreased from 130.51 MPa at 450°C to 126.06 MPa at 495°C and 117.45 MPa at 550°C. Average hardness also decreased from 37.7 VHN to 35.8 VHN and 35.1 VHN, respectively. Elongation showed a non-linear response, decreasing from 19.67% at 450°C to 18.00% at 495°C and increasing again to 19.67% at 550°C. Microstructural observations showed qualitative changes in the appearance, distribution, and uniformity of the observed structure with increasing annealing temperature. Because grain size was not measured quantitatively, the microstructural interpretation was limited to visual comparison. Overall, 450°C produced the highest combination of tensile strength and hardness among the investigated conditions.