Enhanced fatigue properties of cast AZ80 Mg alloy processed by cyclic torsion and low-temperature annealing

In this work, cyclic torsion and low-temperature annealing was applied to a cast AZ80 Mg alloy. After processing, the grains were refined in the outer region of the twisted samples whereas coarse grains remained in the central region. Meanwhile, a large number of {10-12} twins were generated in the outer region but only a few twins were observed in the central region. Both the tensile and compressive yield stresses were increased by grain refinement. At the same stress amplitude in stress-controlled fatigue tests, the strain energy was decreased. The fatigue limit was increased from 70 to 120 MPa, an increase attributed to pre-twinning induced by cyclic torsion.