Degradation behavior of Mg-4Zn-2Ni alloy with high strength and high degradation rate

Abstract

To developed a disintegrating fracturing ball used for multi-stage fracturing stimulation, the Mg-4Zn-2Ni alloy was fabricated and subjected to extrusion at the ram speed of 0.1 mm/s in present work. The results indicated that the as-extruded Mg-4Zn-2Ni alloy mainly contained MgZn2, Mg2Ni and MgZnNi (τ) phase. In addition, both the dynamic recrystallized (DRXed) grain size and DRXed ratio increased accompanied with the increasing extrusion temperature. The compressive strength and degradation rate of Mg-4Zn-2Ni alloy extruded at 200 °C were 512.6 ± 4.2 MPa and 619.35 mm/y, respectively, both of which were higher than the current values for Mg alloys of fracturing balls. The results of electrochemical experiments further verified that Mg-4Zn-2Ni alloy extruded at 200 °C has a faster degradation rate. Among the factors that influencing the degradation rate of Mg alloy, the dislocation density and secondary phase were thought as the key role. Galvanic corrosion consisting of the secondary phase and magnesium matrix preferentially occurs in the unDRXed region with high dislocation density. And then corrosion propagate to the DRXed regions.