Effects of 1.5 wt% samarium (Sm) addition on microstructures and tensile properties of a Mg-6.0Zn-0.5Zr alloy

Effects of samarium (Sm) addition on microstructures and tensile properties of Mg-6.0Zn-0.5Zr (ZK60) alloy under both as-cast and as-extruded states were thoroughly investigated. Similar to some other rare earth (RE) additions, the grains of the as-cast ZK60 alloy were refined and the dominant intermetallic phase was changed from MgZn2 to Mg3Sm2Zn3 (W) phase by Sm addition. After extrusion, the ZK60 sample with Sm addition owns much finer dynamic recrystallization (DRX) grains due to the widely spaced large particles and the fine particles on DRX grain boundaries. Furthermore, some other intermetallic phases were examined in the as-extruded samples such as Mg4Zn7 and Mg7Zn3 in ZK60 sample, Mg22Zn64Sm14 (Z) and Mg21Zn62Sm17 (W') in ZK60+Sm sample. Thirdly, Sm addition results in much finer, much more and more stable spherical nano-scale precipitates in matrix. Finally, Sm addition further improves the strength of ZK60 alloy, with the dominant strengthening mechanisms being revealed as both fine grain strengthening and precipitation strengthening. (C) 2017 Elsevier B.V. All rights reserved.