Microstructures, corrosion behavior and mechanical properties of as-cast Mg–6Zn–2X(Fe/Cu/Ni) alloys for plugging tool applications

Mg–6Zn–2X(Fe/Cu/Ni) alloys were prepared through semi-continuous casting, with the aim of identifying a degradable magnesium (Mg) alloy suitable for use in fracturing balls. A comparative analysis was conducted to assess the impacts of adding Cu and Ni, which result in finer grains and the formation of galvanic corrosion sites. Scanner electronic microscopy examination revealed that precipitated phases concentrated at grain boundaries, forming a semi-continuous network structure that facilitated corrosion penetration in Mg–6Zn–2Cu and Mg–6Zn–2Ni alloys. Pitting corrosion was observed in Mg–6Zn–2Fe, while galvanic corrosion was identified as the primary mechanism in Mg–6Zn–2Cu and Mg–6Zn–2Ni alloys. Among the tests, the Mg–6Zn–2Ni alloy exhibited the highest corrosion rate (approximately 932.9 mm/a) due to its significant potential difference. Mechanical testing showed that Mg–6Zn–2Ni alloy possessed suitable ultimate compressive strength, making it a potential candidate material for degradable fracturing balls, effectively addressing the challenges of balancing strength and degradation rate in fracturing applications.