Full stress tensor determination in a textured aerospace aluminium alloy plate using synchrotron X-ray diffraction

Triaxial strain scanning has been performed on a 7mm thick 7150-aluminium alloy Variable Polarity Plasma Arc (VPPA) weld using synchrotron X-rays. It has been demonstrated that the use of specific advantageous (hkl) peaks that occur in this highly textured aerospace alloy plate permits fast deep measurements in reflection as well as in transmission. The sin⁡2ψ method was also utilised to monitor the variation in deviatoric stress component (σ11−σ33) across the weld in both the test-piece and a comb like reference specimen used to map the changes in stress-free lattice spacings over the weld. The results suggest that microstresses have little effect on macrostress determination, particularly in the Heat Affected Zones (HAZ). Though small in magnitude, the macrostresses still present in the reference specimen can be allowed for to correct the stress tensor in the plate. Maximum tensile longitudinal stress values remain unchanged, whereas the stress condition in some parts of the HAZ is well described as biaxial after the proposed correction