Microstructure, Mechanical Properties and Fracture Behavior of As-Extruded Zn–Mg Binary Alloys

Abstract

In the present work, Zn–(0–1)Mg (wt%) alloys were prepared by casting and indirect extrusion at 200 and 300 °C, respectively. With Mg addition, both the size and amount of second phase Mg₂Zn₁₁ increased, and the equiaxed grains were significantly refined. The extrusion temperature had little influence on Mg₂Zn₁₁, but the grains were refined at low extrusion temperature. For the alloys extruded at 200 °C, as Mg content increased, the tensile yield strength (TYS) increased from 64 MPa for pure Zn to 262 MPa for Zn–1Mg; the elongation increased from 14.3% for pure Zn to 25% for Zn–0.02Mg and then decreased to 5% for Zn–1Mg. For the alloys extruded at 300 °C, as Mg content increased, the TYS increased from 67 MPa for pure Zn to 252 MPa for Zn–1Mg, while the elongation decreased from 11.7% to 2%. The alloy extruded at 200 °C exhibited higher TYS and elongation than the corresponding alloy extruded at 300 °C. The combination of grain refinement and second phase Mg₂Zn₁₁ contributed to the improvement in the TYS, and the grain refinement played a major role in strengthening alloy. Zn–0.02Mg and Zn–0.05Mg alloys extruded at 200 °C show a mixture of cleavage and ductile fracture corresponding to higher elongation, while the other alloys show cleavage fracture.