Wire-arc directed energy deposition (DED) has attracted significant interest for the fabrication of large-sized, lightweight Mg-alloy components. However, these components generally exhibit poor mechanical properties and limited corrosion resistance owing to their inherent residual stress and non-equilibrium microstructures. Herein, laser shock peening (LSP) was adopted to successfully modify the stress state and microstructure of AZ31 Mg-alloy fabricated using wire-arc DED. The influence of LSP on the residual stress, mechanical properties, electrochemical behaviour, and microstructural evolution was systematically investigated. The experimental results indicate that, compared with the as-built specimen, the performance of the LSP-treated specimen was notable, with a ≈63.8% decrease in the corrosion current density and ≈30% and ≈13% decreases in the yield strength (YS) and ultimate tensile strength, respectively. The enhanced corrosion resistance can be attributed to the LSP-induced compressive residual stress, nanograins, and nanoparticles. Nanocrystallisation, particle refinement, dense mechanical twins (MTs), and planar dislocation arrays (PDAs) jointly contributed to the enhancement of the YS. The LSP-induced nanocrystallisation was rationalized by the accumulation of PDAs, the intersection of multiple nano-MTs, and the transformation of nano-MTs blocks into sub-grains and then into nanograins owing to continuous dynamic recrystallisation. The particle refinement mechanism involved dislocation proliferation and the development of dislocation slip bands, which eventually led to fragmentation and separation. Therefore, this study introduces a LSP post-treatment technology for the residual stress regulation, microstructural modification, and performance enhancement of Mg alloys fabricated using wire-arc DED. Based on the ability of LSP to tailor the microstructure and performance of Mg alloys, a novel method of wire-arc DED with online LSP treatment is proposed. This method can achieve in-situ surface strengthening and the integrated formation of large-sized components with complex geometries.

电弧定向能量沉积 (DED) 在制造大尺寸、轻质镁合金部件方面引起了人们的极大兴趣。然而，由于其固有的残余应力和非平衡微观结构，这些部件通常表现出较差的机械性能和有限的耐腐蚀性。其中，激光冲击强化采用 (LSP) 成功地改变了使用线弧 DED 制造的 AZ31 镁合金的应力状态和微观结构。系统地研究了 LSP 对残余应力、机械性能、电化学行为和微观结构演变的影响。实验结果表明，与竣工试件相比，经LSP处理的试件性能显着，腐蚀电流密度下降≈63.8%，屈服强度下降≈30%和≈13%（ YS) 和极限抗拉强度。增强的耐腐蚀性可归因于 LSP 引起的压缩残余应力，纳米颗粒, 和纳米粒子。纳米结晶、粒子细化、致密机械孪晶 (MT) 和平面位错阵列 (PDA) 共同促进了 YS 的增强。LSP 诱导的纳米晶化通过 PDA 的积累、多个纳米 MT 的交叉以及纳米 MT 块转化为亚晶然后转化为纳米晶由于连续动态再结晶 粒子细化机制涉及位错增殖和位错滑移带的发展，最终导致碎裂和分离。因此，本研究介绍了一种 LSP 后处理技术，用于使用线弧 DED 制造的镁合金的残余应力调节、微观结构改性和性能增强。基于 LSP 调整镁合金微观结构和性能的能力，提出了一种采用在线 LSP 处理的线弧 DED 的新方法。该方法可以实现原位表面强化和复杂几何形状的大尺寸构件的集成成型。