EBSD analysis of fatigue crack initiation behavior in coarse-grained AZ31 magnesium alloy

•Fatigue crack initiation mechanism in coarse-grained Mg alloy.•Crystallographic analyses of fatigue crack initiation using EBSD.•Schmid factors calculation of activated slips and twins.•Slip and twin lines analyses based on Euler angles.•Proposal of criteria for both inter- and intergranular fatigue crack initiation.

Plane bending fatigue tests had been conducted to investigate fatigue crack initiation mechanism in coarse-grained magnesium alloy, AZ31, with hexagonal close-packed (hcp) crystallographic structure. The initial crystallographic structure was analyzed by an electron backscatter diffraction (EBSD) method. Subsequently, a fatigue test was periodically terminated and time-series EBSD analyses were performed. Basal slip and primary twin operated predominantly. In a twin band, secondary twin operated, and resulted in the fatigue crack initiation. The crack initiation was strongly affected by Schmid factors in the grains and twin bands.