Improved properties of wire-arc directed energy deposited Al–Mg alloy through laser shock peening

Wire and Arc Direct Energy Deposition (Arc-DED) enables the layer-by-layer deposition of metal filaments to fabricate large-sized components. However, the non-equilibrium solidification properties of 5xxx Al–Mg alloy leads to porosity and poor mechanical properties in as-deposited (AD) components. This study explores the enhancement of Al–Mg alloys microstructure and properties through laser shock peening (LSP) as a surface strengthening method following Arc-DED. We systematically investigate the effects of LSP pulse energy and pulse number on phase composition, pore distribution, and microstructure, revealing the mechanisms of the mechanical property improvements. Results indicate that LSP-induced plastic deformation forms a defect-free zone by closing the pore defects. Furthermore, LSP promotes gradient changes in grain size, low-angle grain boundaries, and dislocation density with depth. The increased dislocation density and energy storage from pulse impacts promote subgrain boundary formation and grain refinement. The application of double (DB) pulses extends LSP's impact zone, further refining the grain structure. By optimizing pulse energy and pulse number, Al–Mg alloys exhibit synergistically improved strength and maintain higher elongation, enhancing their overall performance. For the double-pulse with 4J energy samples, the porosity reduced to 0.01 %, yield strength increased by 89 % (257 MPa) while maintaining 14.2 % elongation.