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Strong local texture is usually formed in friction stir welded (FSW) Mg alloys and varies in different positions of the weld zone. Textural variation has an impact on fracture behavior and caused a poor mechanical property during the transverse tensile tests. However, due to the different stress and strain state between the inner and outer surfaces, the effect of textural variation on fracture behavior in bending tests is still unknown. The present study aims to investigate the relationship between textural variation, twinning activity and fracture behaviors in bending tests by Schmid factor analysis. It is found that sudden change of texture at the transition zone (TZ)/stir zone (SZ) interface and different twinning activity between the TZ and SZ-side have an impact on fracture behavior of bending samples, especially for crack propagation at the TZ/SZ interface for Surface bending test. The effect of textural variation on fracture behavior in bending is highly dependent on the local stress state and it can be well explained by the calculated Schmid factor in terms of the assumed stress state for bending. The present work is helpful for tailoring the local texture to change fracture behavior and improve the joint strength of FSW Mg welds.

Friction stir welding (FSW) has promising application potential for Mg alloys. However, softening was frequently occurred in FSW Mg joints because of the presence of a β-type fiber texture. The present study aims to understand the influence of texture distribution in stir zone (SZ) on deformation behavior and joint strength of FSW Mg welds. AZ31 Mg alloy joints were obtained by FSW with two sets of welding speed and rotation rate. Detailed microstructure and texture evolutions were examined on Mg welds by electron backscatter diffraction (EBSD) techniques. It was found that the changes of welding parameters can affect texture distribution and the characteristic of texture in the transition region between SZ and thermal-mechanical affected zone (TMAZ). As a consequence, the activation ability of basal slip and extension twinning was changed, which therefore influenced joint strength, inhomogeneous plastic deformation and fracture behaviors. The present work provided some insights into understanding the texture–property relationship in FSW Mg welds and indicated that it is effective to tailor the joint performance by texture control.

Friction stir processing (FSP) was successfully applied to modify the microstructure and texture of an Mg-8Gd-5Y-1.1Nd-0.45Zr (wt.%) alloy. Two kinds of original alloys, i.e., solid solution (SS) alloy and aging (AG) alloy were used for a comparative study. The results show that the grains in SZ were greatly refined to 3–4 μm after FSP in both SS and AG alloys. However, the form of rare earth elements (either as solute or forming precipitates) in original alloys can largely influence the homogenization of grains. Uniform equiaxed grains were found in the former, whereas fine grain bands were formed in the latter. Relatively weak texture was formed in stir zone (SZ) of the Mg–Gd–Y–Nd–Zr alloy after FSP. The texture evolution in SZ is similar to many previous reports on FSW of AZ and ZK series Mg alloys. Both types of continuous and discontinuous dynamic recrystallizations (DRX) were observed in the transition region between SZ and base material in AG-FSP alloy.