Comparison of the microstructure and mechanical properties of a ZK60 alloy with and without 1.3 wt.% gadolinium addition

The influence of 1.3 wt.% Gd on microstructure and mechanical properties of cast and hot-extruded ZK60 (Mg–6Zn–0.4Zr) alloy was studied in different conditions, including as-cast, cast-T4, cast-T6 and extruded-T5 and extruded-T6 at the extrusion temperatures of 623, 673 and 723 K. The results show that the addition of Gd leads to a considerable reduction of the age-hardening response and a small decrease of tensile yield strength (TYS) and ultimate tensile strength (UTS) in cast-T6 and extruded-T5 conditions, owing to the formation of Mg–Zn–Gd intermetallic compound which consumes some of Zn atoms in the matrix. However, the grain refinement caused by the addition of Gd is remarkable, which compensates partly for the loss of TYS and UTS due to the consumption of Zn in the matrix and improves the elongation of the alloy, especially at the elevated temperature.