A novel Mg-Gd-Y-Zn-Cu-Ni alloy with excellent combination of strength and dissolution via peak-aging treatment

Abstract

Inferior absolute strength and dissolution properties are the main bottlenecks for the widespread application of dissolvable magnesium alloys in complex working environments for unconventional oil and gas resources. Here, a novel functional peak-aged Mg-9.5Gd-2.7Y-0.9Zn-0.8Cu-0.4Ni (wt.%) alloy for fracturing tools is reported, and it possesses an ultimate tensile strength of 457.6 MPa, ultimate compressive strength of 620.7 MPa and dissolution rate of ∼43.7 mg·cm−2·h−1 in 3 wt.% KCl solutions at 93 °C. The excellent strength of the aged-alloy is primarily attributed to the combination of grain refinement, long-period stacking ordered (LPSO) strengthening, and precipitation strengthening induced by stacking fault and β’ phase, among which the precipitation strengthening is dominant. Further investigations confirm that the corrosion is triggered from the micro-galvanic coupling between the Mg matrix and the cathodic lamellar and block LPSO phases. Strip-shaped corrosion pits along with LPSO phases are subsequently formed, significantly accelerating corrosion. The β’ precipitates can effectively improve the strength without compromising the dissolution rate because of their nanoscale size. This study provides an excellent material selection for dissolvable fracturing tools and presents a strategy by which a synergistic combination of strength and dissolution rate is achieved via peak-aging treatment.