2004 Volume 45 Issue 6 Pages 1833-1838
The fatigue properties in the Al-Mg-Mn alloy sheet subjected by the continuous cyclic bending (CCB) and annealing have been investigated. By the CCB and subsequent annealing, the gradient microstructure with coarse-grained surface layers and fine-grained central layer is produced in the sheet. The fatigue life of the CCBent and annealed sheet is 2—4 times longer than that of the as-received one. The existence of the coarse-grained surface layers makes the crack propagation rate lower by a factor of 1/2 to 1/3. The fatigue crack growth in the sheet consisting of such different microstructure layers is characterized by the fractography. Further, factors improving the fatigue properties are discussed.