The effects of texture and extension twinning on the low-cycle fatigue behavior of a rolled magnesium alloy, AZ31B

The effect of texture on the low-cycle fatigue behavior of a rolled magnesium alloy, AZ31B, was studied at room temperature. It is shown that the Coffin-Manson and Basquin relationships can be used to describe the fatigue resistance of the alloy. The alloy loaded along the rolling direction exhibits only slightly better low-cycle fatigue resistance than that loaded along the transverse direction, due to the in-plane texture symmetry. The in-plane cases exhibit better fatigue behavior than the through-thickness loading. Neutron diffraction and synchrotron diffraction were employed to assist in making mechanistic understandings for the findings. The fundamental difference in the low-cycle fatigue behaviors between the in-plane and through-thickness loadings is attributed to the different activation sequences of twinning and detwinning mechanisms involved and, particularly, the greater requirement for c-axis compression of the grains during the through-thickness tests. The different activation sequences are essentially determined by the initial crystallographic texture, such that the inverted hysteresis-loop shapes are observed. (C) 2010 Elsevier B.V. All rights reserved.