506 Observation of Fatigue Crack Initiation Mechanism of High-Strength Aluminum Alloy by Using Atomic Force Microscopy

Fatigue tests of a high-strength aluminum alloy 7075-T657 were conducted under the constant amplitude in air. The fatigue crack initiation and propagation process were observed by using a optical microscopy and an atomic forced microscopy (AFM). Before crack initiation, no slip-bands were observed either by optical microscopy or AFM. After crack initiation, micro cracks were observed in front of the main crack.