2012 Volume 6 Issue 5 Pages 361-373
The fatigue properties of the 5056 aluminum alloy, which is the highest Mg-rich alloy among the commercial Al-Mg alloys and exhibits high work hardening and strain aging, was investigated. Rotating-bending tests using smooth specimens were performed at room temperature with the stress ratio R=-1 and frequency of stress cycle f =55 Hz. The experimental results showed that a distinct fatigue limit as in the case of steel existed on the S-N curve. Surface observations using the replica method revealed a wavy pattern around the second phase particle for N=106-107, but no non-propagation cracks were observed. It was speculated that the observed fatigue limit appeared as a result of high work hardening rate and strain aging in the heavily deformed zone, and the fatigue cracks did not initiate from this zone up to the maximum number of stress cycle, N=3.5×107, in the present study.
