Microstructure Characteristic and Mechanical Properties of High-Strength Mg-Nd-Zn-Zr Alloy Seamless Tube Produced by Integrated Extrusion

Large size seamless tubes of Mg-3.0Nd-0.4Zn-0.4Zr alloy (NZ30K, in weight percent) were prepared by integrating backward extrusion with forward extrusion. Microstructure, mechanical properties, aging behavior and texture of the tubes were investigated. The microstructure of as-extruded tube is characterized by the blend of considerably elongated grains and fine equiaxed grains. The maximum values of yield strength and ultimate tensile strength, i.e., 191 and 245 MPa, were obtained in the as-extruded tubes, and these values were increased to 212 and 267 MPa in the peak-aged tubes (T5), implying an increasing ratio of 9 and 11%, respectively. The peak value of the Vickers’ micro-hardness of the NZ30K tubes extruded at 673, 723 and 753 K are 66, 64 and 60 (kilogram-force per square millimeter), respectively. The texture of NZ30K tube is weak, the primary mechanism behind which is suggested to be the particle-induced nucleation responsible for the promotion of recrystallization.