Formability, mechanical and corrosive properties of Mg–Nd–Zn–Zr magnesium alloy seamless tubes

Some large Mg–3.0Nd–0.2Zn–0.4Zr (NZ30K) magnesium alloy seamless tubes were prepared by forward extrusion. The as-extruded tubes were cooled in the air or by spraying liquid N2 after extrusion. The formability, mechanical and corrosive properties of the NZ30K magnesium alloy seamless tubes were investigated. The experimental results show that seamless NZ30K tubes with an outer diameter of 110 mm and inner diameter of 90 mm can be produced by forward extrusion and the tubes have good roundness, concentricity and straightness even without any straightening. The tensile results show that the maximum ultimate tensile strength, yield strength and elongation of the extruded tubes cooled in the air and by spraying liquid N2 are 306.3 and 314.6 MPa, 250.4 and 270.3 MPa, 14.2% and 15.6%, respectively. The corrosion rates of the as-extruded tubes cooled in the air and by spraying liquid N2 immersed in 5% NaCl solution for 3 days are 0.225 and 0.234 mg cm−2 day−1, respectively, which are a little inferior to the as-cast, T4 and T6 NZ30K alloys, but much lower than that of AZ91 alloy. Localized corrosion is suggested to be its corrosion pattern.