Effect of Gd addition on the age hardening response of Mg–6Zn-1Mn alloy

Abstract

The effect of Gd addition on the microstructure and mechanical properties of as-aged Mg–6Zn-1Mn (ZM61) alloy were investigated. The results showed that coarse second phase particles containing both Zn and Gd elements were detected after the addition of Gd element, leading to reduce the amount of Zn available as solutes in the α-Mg matrix. Compared with ZM61, the peak aging hardness had a little difference and the peak aging time was shortened with micro amount of Gd addition, while the hardness decreased significantly for the alloys with high Gd addition. The age hardening response was mainly dictated to the precipitation of fine rod-like β1′ phase, and the number density of β1′ phase was related to the Zn content in the α-Mg matrix. Aging treatment could effectively improve the strength of alloys with minor Gd addition and it was of little significance for alloys with high Gd content. The as-aged ZMG61-0.2 exhibited optimal mechanical properties, and the yield tensile strength, ultimate tensile strength, elongation were 360MPa, 390MPa, 8.3%, respectively.