Influences of Gd on the microstructure and strength of Mg–4.5Zn alloy

Microstructure and mechanical properties of peak-aged Mg–4.5Zn–xGd (x = 0, 0.5, 1.0 and 1.5 wt.%) alloys have been investigated. The results showed that the grain size of the alloys was refined gradually with increasing Gd. Mg5Gd and Mg3Gd2Zn3 phases were found in the Gd-containing alloys. The strengths were greatly improved with Gd additions, and the highest strength level was obtained in the Mg–4.5Zn–1.5Gd alloy, in which the ultimate tensile strength and yield strength were 231 MPa and 113 MPa, respectively. Through comparing with the Mg–4.5Zn alloy, the increments of ultimate tensile strength and yield strength were 22 MPa and 56 MPa, respectively. The improved strength was mainly correlated to the grain refining effect, the strengthening effect of the Mg5Gd and Mg3Gd2Zn3 phases and also the hardening effect of the solutioned Gd atoms.