Improvement of Fatigue Properties by Means of Continuous Cyclic Bending and Annealing in an Al-Mg-Mn Alloy Sheet

Abstract

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.

Enhancing Fatigue Properties of Nanostructured Metals and Alloys

“…Having a combination of large and small grains presumably offers both the effects of higher strength associated with the smaller grains and the enhanced ductility associated with larger grains. Based on this hypothesis, other researchers have successfully demonstrated the prospect of enhancing total fatigue life by nanostructuring surfaces where cracks are most likely to initiate and having larger grains beneath the surface to mitigate crack propagation [8][9][10].…”

Ultrafine-Grained Materials Fabrication with High Pressure Torsion and Simulation of Plastic Deformation Inhomogeneous Characteristics

“…Recently, several processing techniques existing metal forming processes have been designed such as continuous cyclic bending (CCB), twist extrusion (TE), equal channel angular pressing (ECAP), and so on. New techniques are often proposed, all of them rely on the idea that a high hydrostatic pressure is necessary to avoid cracking, for a review see [16][17][18][19][20][21][22][23][24][25]. Among these SPD methods, the HPT process is particularly noteworthy because it can produce finer grains, with a higher fraction of high-angle grain boundaries, than can the other SPD methods [5,8,[26][27][28][29].…”