High strength-ductility and rapid degradation rate of as-cast Mg-Cu-Al alloys for application in fracturing balls

Specially designed Mg-Cu-Al alloys were prepared for the application in fracturing balls.In comparison to Mg-2.5 Cu alloy,Mg-2.5 Cu-6.0 Al alloy exhibits an improved compressive strength of 378 MPa and compressive strain of 27%,combined with a high degradation rate of 383 mm/y.Two kinds of second-phases are found in Mg-Cu-Al alloys,i.e.MgAlCu andβ-Mg_(17)Al_(12)+Al_(2)Cu phases.They form a discontinuous network and act as cathodes for micro-galvanic corrosion,leading to a high degradation rate.Moreover,the addition of Al could improve the strength and ductility simultaneously in Mg-Cu alloys.The enhancement of strength primarily arises from the solid-solution strengthening and second-phase hardening.A high density of basal,non-basal dislocations and stacking faults were activated upon mechanical deformation.This accounts for the good ductility in Mg-Cu-Al alloys.