The long period stacking ordered (LPSO) phase is a key strengthening precipitate phase in the Mg-Y-Zn based alloys. Fully controlled by the chemical ordering and stacking faults, the LPSO phase could be strongly modified by alloying elements. This work explored the effect of trace Sn addition on the Mg-6Y-2Zn alloy, with an emphasis on the LPSO phase and corresponding changes of mechanical properties in the as-cast, as-annealed and as-extruded states. Results show that the 18R LPSO phase forms as needles and distributes at grain boundaries. Meanwhile, its length and density are stimulated dramatically by the Sn addition in the as-cast state. After annealing, the content of the 18R increases accompanied by the change of morphology shapes from needle to block. Additionally, fine 14H LPSO lamellas are precipitated both in grains and between 18R phases. In contrast to the as-annealed Sn-free alloy, the area fraction of 18R phase in the Sn-containing Mg alloy increases from 35% to 58%, the 14H is also promoted to a certain extent. Tensile tests conducted on as-extruded state revealed remarkable mechanical properties improvement in the Sn-containing alloy over its ternary equivalents. The relevant mechanisms are also investigated in detail.

在Mg-Y-Zn基合金中，长期堆积有序（LPSO）相是关键的强化析出相。LPSO相完全受化学有序和堆垛层错控制，可以通过合金元素强烈地改性。这项工作探索了微量锡添加对Mg-6Y-2Zn合金的影响，重点是LPSO相以及在铸态，退火态和挤压态下力学性能的相应变化。结果表明，18R LPSO相形成为针状并分布在晶界。同时，在铸态下添加锡会极大地刺激其长度和密度。退火后，18R的含量增加，伴随着针形到块形的形态变化。此外，细小14H LPSO薄片会在晶粒内和18R相之间沉淀。与退火后的无锡合金相比，含锡的镁合金中18R相的面积分数从35％增加到58％，14H也得到了一定程度的促进。在挤压状态下进行的拉伸试验表明，含锡合金的机械性能明显优于其三元当量。还详细研究了相关机制。