Structure–property relationships and residual stress quantification of a friction stir spot welded magnesium alloy

Structure–property relationships and spatial residual stress distribution in a friction stir spot welded magnesium alloy (AZ31) sheet was investigated to elucidate the incipient deformation mechanisms and welding process parameters. Experimental results revealed a decrease in the tensile and compressive yield strengths, as well as an increase in ductility and grain size, as the tool rotational speed and shoulder depth increased. Residual stresses were measured using neutron diffraction, and a strong dependency was found between the grain size, residual stress and the welding parameters.