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-2.5Cu alloy, Mg-2.5Cu-6.0Al 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 and β-Mg₁₇Al₁₂+Al₂Cu 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.