In this study, it is aimed to investigate effect of the grain refinement on the mechanical properties of the AA 6082. The micro structure which plays crucial role in determining the mechanical properties of the alloys is varied according to grain size, chemical composition and cooling rate. The prescription was prepared by determining the chemical composition range according to the standard (TSE-EN-573). The casting experiments were performed on the 6082 aluminium alloy which belongs to Al-Mg-Si system with different percentages of grain refinement (AlTi 5 B 1 ) and chemical composition. Heat treatment that is homogenization and artificial aging was applied after casting and extrusion process, respectively. The microstructure analysis and mechanical tests were done on the produced samples in order to understand the structural and mechanical strength of the material. The experimental results showed that using the grain refinements is contributed to increasing the mechanical properties. It was observed that the mechanical strength values increased by 17% after the reduction of the grain size by 69% with the 0.11% addition of the AlTi 5 B 1 master alloy.