In this research, end milling was carried on pre and post thermally treated AA6061-T6 aluminum alloys. Heat treatment with aging time of 8 hours was used to vary the material properties (mechanical properties) of the AA6061-T6 alloy. The variation of material properties such us tensile strength, yield strength, hardness and ductility having significant effects on the burr formation. The burr formation was due to the transition of materials when the toll passes over the material. The materials with higher hardness and yield strength offer higher resistance to plastic deformation. Moreover the material transition in the lateral direction with higher cutting speed and depth of cut is negligible for materials with higher hardness and yield strength leading to reduced burr height. The burr height of post heat treated materials was lesser than the parent because of higher yield strength, hardness and lesser ductility..