The deformation modes and transferability during low-cycle fatigue of Mg and Mg–3Y alloy

Quantitative assessment of the microstructural factors controlling the fatigue crack initiation mechanisms in AZ31 Mg alloy

“…These results are in agreement with the large tension-compression anisotropy in the cyclic stress-strain curves, which was due to the activation of pyramidal slip during the tensile part of the cycle as basal slip was not able to accommodate the plastic deformation because of the strong basal texture. Overall, the conclusions of slip trace analysis for the fatigue deformation mechanisms are in agreement with those reported in other studies of Mg alloys deformed in different directions and with different strain amplitudes [11][12][13]16,25].…”

“…basal slip and twinning) in the samples deformed along 45º RD-ND (representative of Mg alloys with weak basal texture) are in good agreement with those reported in the literature during fatigue of AZ31 Mg alloy along 45º RD-ND and of weakly textured Mg-3wt.% Y alloy deformed at ∆ɛ/2 = 1%[11][12][13]17].…”

“…Basal slip traces were not found in this specimen. However, it is important to mention that basal slip should also be a dominant deformation mechanism because most grains were suitable oriented for basal slip [11,13,16,28]. The number of grains with slip traces increased to 16% in the specimen deformed along 45º RD-ND at ∆ɛ/2 = 2%, and approximately one-half of them showed elongated twins.…”

“…Taking into account the orientation of most of the grains (Fig. 2b), basal slip is expected to be the dominant deformation mechanism together with tensile twinning [11][12][13]16]. In addition, grains twinned during the compressive part of the cycle will detwin in the tensile part and viceversa.…”

“…These phenomena may be particularly relevant in the case of Mg alloys, which present the highest plastic anisotropy due to the significant differences in the critical resolved shear stress between basal and non-basal slip systems. Moreover, twinning is easily activated in suitably oriented grains in Mg alloy polycrystals and is followed by detwinning during reversed deformation, leading to continuous twinning-detwinning during cyclic loading [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21].…”