Effects of Cu on the microstructure and properties of Mg-6Al-1Zn-1.0Sn dissolvable magnesium alloy
Dissolvable magnesium alloys,employed as bridge plugs and fracturing balls in enhanced oil and gas field extraction,must exhibit excellent strength,plasticity,and rapid dissolution rates.However,the currently used dissolvable magnesium alloys are often limited by their inadequate mechanical and dissolution properties.In this study,Mg-6Al-1Zn-1.0Sn alloy was used as a base material,with varying Cu content(x=0.5,1.5,and 2.5)added.The Mg-6Al-1Zn-1.0Sn-xCu(x=0.5,1.5,and 2.5)alloys were prepared through casting and ex-trusion methods.Microstructure and morphology of the alloys were characterized using scanning electron mi-croscopy(SEM),X-ray diffraction(XRD),and optical microscopy(OM).The effects of Cu addition on the dissolution rate and mechanical properties of Mg-6Al-1Zn-1.0Sn-xCu(x=0.5,1.5,and 2.5)alloys were inves-tigated using Tafel curves,weight loss measurements,and room temperature tensile tests.The results indicate that the addition of Cu forms AlCuMg phases,which enhance the nucleation rate during solidification,refine the grains,and improve the dissolution uniformity of Mg-6Al-1Zn-1.0Sn-xCu(x=0.5,1.5,and 2.5)alloys.With increasing Cu content and solution treatment temperature,the dissolution rate of Mg-6Al-1Zn-1.0Sn-xCu(x=0.5,1.5,and 2.5)alloys increases while the tensile strength decreases,and the elongation improves.The Mg-6Al-1Zn-1.0Sn-0.5Cu alloy,subjected to a solution treatment at 425 ℃ for 2 hours and aging at 180 ℃ for 24 hours,exhibited a tensile strength of 290 MPa,a yield strength of 194 MPa,and an elongation of 14.0％.The dissolution rates in 3.5 wt％KCl solution at 60 ℃ and 90 ℃ were 28.65 mg/(h·cm2)and 32.52 mg/(h·cm2),respectively.This study provides a theoretical reference for the development of dissolvable magnesium al-loy materials for shale gas extraction.
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