Interface characteristics and repair behavior of AZ31B magnesium alloy processed by wire-feeding additive friction stir deposition

Mechanical scratch and wear will produce linear groove-like damage on the surface of AZ31B magnesium alloy components can significantly affect the properties of the alloy, yet effective repair methods remain lacking. This study introduces an innovative friction stir deposition additive repair technique incorporating continuous wire feeding. Single-pass deposition repair was carried out on the surface of AZ31B magnesium alloy sheets with two prefabricated (U/T-shaped) damaged interfaces. A comprehensive investigation revealed distinct microstructural characteristics among the repair zone (RZ), thermo-mechanically affected zone (TMAZ), and base-material zone (BZ). Remarkably, the RZ and TMAZ regions exhibited grain refinement of 95.1% and 97.1%, respectively, compared to the base material. This substantial refinement primarily results from varying degrees of recrystallization induced by different thermo-mechanical forces within the repair areas. Some new grains inherited and strengthened the texture of the base material, enabling the tensile properties of the repair area were almost identical to of those of the base material. However, the presence of intermediate β-Mg (Mg 17 Al 12 ) phase, identified as a brittle constituent, was found to reduce repair ductility. Comparative analysis demonstrated that the vertical T-shaped structure amplifies the shear effect during repair process, consequently exhibiting superior repair performance relative to the smooth U-shaped structure. The findings provide crucial insights into microstructure-property relationships in repaired magnesium alloys and present a viable solution for restoring damaged components.