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

Abstract

• As-cast Mg-2.5Cu-xAl (x = 4.5, 6.0 wt.%) alloys were developed for application in fracturing balls. • The degradable Mg-2.5Cu-6.0Al alloy exhibits a combined high compressive strength (378 MPa), good compressive strain (27%) and rapid degradation rate (383 mm/y). • The addition of Al could improve the strength and ductility simultaneously in Mg-2.5Cu alloy. • A discontinuous network of β-Mg 17 Al 12 +Al 2 Cu and MgAlCu phases is formed in the immersion tests, acting as cathodes to accelerate micro-galvanic corrosion. 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-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.