Effect of Ni on the microstructure, mechanical properties and corrosion behavior of MgGd1Nix alloys for fracturing ball applications

The effects of Ni addition on the mechanical properties, corrosion behaviors, and corrosion mechanism of MgGd1Nix alloys have been investigated by compressive tests, weight loss, hydrogen evolution, and scanning electron microscopy. The results show that the constitution of the second phase is large dependence on Ni/Gd molar ratios, which can transform from LPSO(long-period stacking ordered)+Mg5Gd, LPSO to eutectic phase. In addition, with increasing Ni/Gd molar ratios, the content of second phase increases gradually, while the LPSO phase shows a parabola relationship. Furthermore, the formation of Ni-containing LPSO phase not only can improve the strength but also accelerate the degradation of Mg alloys owing to the galvanic corrosion. The optimal properties with ultimate compressive strength, degradation rate are 340 MPa, 2066 mm/y for MgGd1Ni0.75, respectively, which can meet the engineering application standard of fracturing ball and can be used as candidate materials for fracturing ball. (C) 2021 Published by Elsevier Ltd on behalf of Chinese Society for Metals.

Automated summary

The composition of the second phase in MgGd1Nix alloys significantly affects the strength and degradation rate, with an increasing Ni/Gd molar ratio leading to a gradual increase in second phase content and a parabolic relationship with the LPSO phase. The formation of Ni-containing LPSO phase improves strength but accelerates degradation due to galvanic corrosion, with optimal properties observed in MgGd1Ni0.75 for engineering applications.