This study investigates the synergistic effects of multi-step surface modification on the properties of AZ31 magnesium alloy. Five distinct treatments were applied: Friction Stir Processing (FSP), FSP followed by Laser Surface Remelting (FSP + LSR), phytic acid (PA) conversion coating, FSP + PA, and a triple hybrid treatment of FSP + LSR + PA. The microstructural evolution, hardness, and corrosion behavior were systematically characterized using optical microscopy, X-ray diffraction, microhardness testing, and electrochemical measurements. The results demonstrate that FSP effectively refined the grains and reduced the β-phase content in the stir zone without significantly altering the sample dimensions. The subsequent LSR treatment further modified the sample profile, produced additional grain refinement in the remelted zone, and led to a further reduction in β-phase content. Among all samples, the FSP + LSR treated specimen exhibited the highest microhardness of 71.47 HV. In contrast, the triple hybrid FSP + LSR + PA treatment yielded the most pronounced improvement in corrosion resistance, achieving the lowest corrosion current density of 9.67 × 10−6 A·cm−2.
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