Neutron Diffraction Study of Residual Stresses in Large Welded 5B70 Aluminum Alloy Conical Structures

Managing residual stresses (RS) in large-scale welded structures is critical for ensuring structural integrity in high-performance applications. This study characterizes the RS evolution in a 5B70 aluminum alloy scaled-down conical shell manufactured through roll-bending and electron beam welding. Neutron diffraction was employed for non-destructive, depth-resolved measurements due to its superior penetration in aluminum alloys. Investigations were conducted on both simplified welded plates and the complex conical assembly to decouple manufacturing influences.

Results reveal significant RS gradients across the thickness: outer surfaces exhibited high tensile peaks (~200 MPa) where bending and welding stresses superimpose, while inner surfaces remained predominantly compressive. In the full conical assembly, circumferential RS followed a "W-shaped" distribution, with triaxial tensile peaks (125–150 MPa) identified at weld centers. Furthermore, the RS field demonstrated pronounced path dependency related to the welding sequence. The weld center within 0–5 mm depth of the outer surface was identified as the critical zone for potential crack initiation due to high-magnitude triaxial tension and steep stress gradients. This research provides a quantitative experimental basis for optimizing manufacturing parameters and performing structural reliability assessments for large-scale, thin-walled welded components.