Microstructure, texture and residual stress in a friction-stir-processed AZ31B magnesium alloy

Spatial variations of microstructure, hardness, chemical composition, tensile behavior, texture and residual stresses were investigated in a friction-stir-processed (FSP) AZ31B magnesium alloy. The residual stresses were measured using two different methods: neutron diffraction and the contour method. No significant variations in the hardness and chemical compositions were found in the FSP zones, including the severely deformed stir zone (SZ), which showed a finer grain size compared to the heat-affected zone and base material. On the other hand, significant changes in the tensile yield strength, texture, and residual stresses were observed in the FSP zones. The relationship between the texture variations and yield strength reduction; and its influence on the decrease in the residual stress near the SZ is discussed. Finally, the residual stresses measured by neutron diffraction and the contour method are compared and the effect of the texture on neutron diffraction residual stress measurements is discussed.