Investigation of residual stress distribution and texture evolution in AA7050 stationary shoulder friction stir welded joints

Abstract

A study of the residual stress distribution and texture evolution in stationary shoulder friction stir welded (SSFSW) AA7050 plate through non-destructive energy-resolved neutron imaging (NI), monochromatic neutron diffraction (ND) and destructive contour method (CM) is described in this paper. The presence of Bragg edges in the neutron transmission spectra are shown to be effective in determining the longitudinal residual stress and compare well with results obtained by ND and CM. The texture in the weld zone and base metal has been mapped by contrast in the narrow-energy transmission image combined with an analysis of the Bragg edges in the transmission spectra at each pixel showing agreement with the results obtained by electron backscatter diffraction (EBSD) mapping. The ND results were complicated by plastic anisotropy effects in the rolled plate which meant that different reference stress-free lattice spacings were required at each point in the 3 principal directions for this material. NI and CM were unaffected by texture effects in determining residual stress. Compared to conventional techniques, NI is shown to be an effective way of quantifying both texture and residual stress in one shot.