Accelerated degradation rate of high-strength Mg-4Y-1Zn alloy by Cu addition for degradable bridge-plug applications

To find good candidate materials for degradable bridge-plugs used in shale oil or gas exploitation, a novel hot extruded Mg-4Y-1Zn-1Cu alloy with long period stacking order (LPSO) phase and excellent mechanical properties and rapid degradation rate was fabricated. Compared with the Mg-4Y-1Zn alloy, the compressive properties of Mg-4Y-1Zn-1Cu alloy are dramatically enhanced by adding Cu, with a compressive strength of 480 MPa, which can be attributed to the formation of fine-grains and the strengthening LPSO phase distributed within the substrate. Furthermore, Mg-4Y-1Zn-1Cu alloy shows a rapid degradation rate as demonstrated by immersion tests and polarization curves, with about 30 times higher corrosion rate than Mg4-Y-1Zn alloy, which can be attributed to the 14H-type LPSO phase containing Cu with high corrosion potential and high fraction grain boundaries.