Interface interlocking enhances mechanical strength of wire-arc directed energy deposited Mg-Al-Si/Mg-Gd-Y-Zn bimetals

Abstract

A novel Mg-Al-Si/Mg-Gd-Y-Zn bimetals with interlocking structure is manufactured using wire-arc directed energy deposition, with an interface remelting strategy. The results indicate that the bimetallic interface of non-remelting is composed of a composition transition region, with 18R-long-period stacking ordered phase and large-sized mixtures of Mg₁₇Al₁₂, Mg₂Si as well as Mg(Gd, Y) phases. After remelting, the bimetallic interface transforms into an interlocking structure. The grains near the interface are refined and shrinkage pores are eliminated. The yield strength of bimetal increases by 18.8 %. The fracture surface shows that the non remelted sample fractures in the transition zone, while the remelted sample fractures in the Mg-Al-Si alloy region. The digital image correlation results indicate that the interlocking structure can release the internal stress of the bimetallic interface. The improved strength mainly derives from interlocking structure and grain refinement strengthening.