Effect of Cu Micro-Alloying on the Microstructure and Properties of Mg-Gd-Y-Zn Based Alloy Applied as Plugging Tools

Abstract

Dissolvable functional magnesium alloys are attracting strong attention due to the prominent advantages of high strength and suitable dissolution rate. Here, the effect of Cu micro-alloying (0, 0.4, 0.8 wt.%) on the microstructure, mechanical and corrosion properties of Mg-9.5Gd-2.7Y-0.9Zn alloys applied as plugging tools are investigated. It is found that with the increase of Cu contents, the amount of block 14H long-period stacking ordered (LPSO) phase gradually increases, which effectively impedes dislocation motion, promotes dynamic recrystallized (DRXed) behaviors, and refines the grains. Meanwhile, the texture intensity is weakened. The alloy with 0.8 wt.% Cu obtains the higher yield strength compared with Cu-free alloys, which is mainly ascribed to the improved grain boundary strengthening by refining grain size. Compared with Cu-free alloy, the Cu-containing alloy exhibits more severe corrosion due to the larger Volta potential difference. Moreover, the fraction of the block LPSO phase serving as cathode for the 0.8Cu alloy is higher than that of the 0.4Cu alloy, which promotes the formation of more micro-galvanic coupling and accelerates corrosion. Ultimately, the Mg-9.5Gd-2.7Y-0.9Zn-0.8Cu alloy exhibits an ultimate tensile strength of 380 MPa, tensile yield strength of 331 MPa, and decent corrosion rate (16.8 mg·cm -2 ·h -1 at 93 °C in 3 wt.% KCl solution). This work strengthen understanding the role of Cu in designing high-strength dissolvable Mg-RE alloys.

Keywords: Mg-Gd-Y-Zn-Cu alloy, LPSO, Grain refinement, Mechanical property, Corrosion behaviors.