Influence of Nd addition on microstructures and mechanical properties of a hot-extruded Mg-6.0Zn-0.5Zr (wt.%) alloy

Influence of 1.5 wt% Nd addition on microstructures and mechanical properties of the as-extruded Mg-6.0Zn-0.5Zr (ZK60) alloy was studied. The results illustrate that Nd addition clearly refines dynamic recrystallized grains but has almost no influence on texture. Additionally, the intermetallic phases were significantly altered by Nd addition. In ZK60 alloy, the coarse intermetallic phases are MgZn2, Mg21Zn25, Mg4Zn7, MgZn and I-phase, while MgNdZn3 (W), Mg43Zn51Nd6 (T), MgZn2 and Nd-enriched MgZn after Nd addition. Also, three kinds of new orientation relationships (ORs) between MgZn2 or its twin domain and Mg were revealed in this work while both MgZn2 and W were found to be coherent with T following identical ORs. Furthermore, the fine precipitates are with sizes of similar to 20 nm and were confirmed as MgZn2, MgZn2 + MgZn and Mg4Zn7 + MgZn2 in ZK60 alloy while new spherical Guinier Preston (G.P.) zones with sizes of similar to 5 nm after Nd addition. Finally, the above microstructural modifications because of Nd addition result in ultra-high strength for ZK60 alloy, with tensile yield strength being approximately 408 MPa. (C) 2019 Elsevier B.V. All rights reserved.