Fracture toughness of aluminium alloy 7075-T6 in the as-cast condition

Abstract The fracture toughness of high strength aluminium alloy 7075-T6 in the as-cast condition was studied using standard compact tension specimens with thicknesses ranging from 4 to 25 mm with a 3 mm incremental interval. ASTM Standard E 399-74 for plane strain fracture toughness determination was adhered to in the investigation. The results show that the ASTM-E 399 Standard minimum thickness requirement occurs before the fracture toughness Kc reaches the limiting value KIc but that for the material tested, although Kc decreases as the specimen thickness increases within the valid thickness range KQ remains constant and valid over this thickness range and thus KIc can be determined. The plane strain fracture toughness is 27.5 MPa m 1 2 . KIc values obtained from specimens of different crack plane orientations were found to remain constant, indicating the lack of anisotropy in the material. This is expected, however, for material in the as-cast condition.