Enhanced mechanical properties and degradation rate of Mg–Ni–Y alloy by introducing LPSO phase for degradable fracturing ball applications

Abstract

In this work, as-cast Mg–Ni–Y alloys were proposed to develop a feasible material for fracturing balls, and their mechanical performance and corrosion behavior were systematically investigated. Long period stacking order (LPSO) phase was firstly introduced to improve both the mechanical properties and degradation rate of magnesium alloys. With the increase of LPSO phase, the compressive strength was improved significantly, while the elongation of the alloys decreased owing to the relatively brittle nature of LPSO phase. Due to the higher corrosion potential of LPSO phase, the LPSO phase can accelerate the corrosion process by providing more micro-couples. However, the LPSO phase would serve as the corrosion barrier between the corrosion medium and the matrix when the contents of LPSO phase are too high in Mg92.5Ni3Y4.5 and Mg87.5Ni5Y7.5 alloys. As-cast Mg97.5Ni1Y1.5 alloy with satisfactory mechanical properties and rapid degradation rate was successfully developed, exhibiting a high degradation rate of 6675 mm/a (93 °C) in 3 wt.% KCl solution and a favorable ultimate compressive strength of 410 MPa. The degradation rate of Mg97.5Ni1Y1.5 alloy is 2–5 times of the current commercial magnesium alloy fracturing materials. Keywords: Mg–Ni–Y magnesium alloys, Fracturing ball, LPSO phase, Degradation rate, Mechanical properties