Microstructure and mechanical properties of Mg–Zn–Y alloys with different Zn/Y atomic ratios with or without artificial cooling (AC) extrusion were systematically investigated in this work. The results show that bimodal microstructure consisting of submicron dynamic recrystallized (DRXed) grains with high fraction of low-angle grain boundaries (LAGBs) and elongated unDRXed grains was formed in Mg_98.7Zn₁Y_0.3 alloy with AC extrusion. The AC process effectively limits the growth of precipitated phases, and large amount of nanoscale precipitates were dynamically precipitated during the extrusion process. AC extrusion could effectually refine the lamellar 14H LPSO phases and inhibit the transition from stacking faults to LSPO phases in Mg₉₈Zn₁Y₁ alloy and the narrow LPSO phase in Mg₉₈Zn₁Y₁-AC alloy which could promote the nucleation of DRXed grains. The AC extrusion significantly improves the strength of Mg–Zn–Y alloys. Owing to AC extrusion, the strength improvement of Mg_98.7Zn₁Y_0.3 alloy is mainly attributed to fine grain strengthening, dislocation strengthening, and nano-phases precipitation strengthening. After AC process, more fine grains and nano-phases jointly strengthen the Mg₉₈Zn₁Y₁ alloy. The Mg₉₈Zn₁Y₁ alloy obtains optimal mechanical properties after extrusion at 623 K, with ultimate tensile strength (UTS) of 406 MPa, yield strength (YS) of 388 MPa, and elongation (EL) of 5.6%.

本文系统地研究了经过或不经过人工冷却（AC）挤压的不同 Zn/Y 原子比的 Mg-Zn-Y 合金的显微组织和力学性能。结果表明，采用AC挤压在Mg _98.7 Zn ₁ Y _0.3合金中形成了由亚微米动态再结晶（DRXed）晶粒和高比例的小角度晶界（LAGB）和拉长的未DRXed晶粒组成的双峰显微组织。 AC工艺有效限制了析出相的生长，在挤压过程中动态析出大量纳米级析出物。 AC挤压可以有效细化Mg ₉₈ Zn ₁ Y ₁合金中的层状14H LPSO相并抑制从堆垛层错到LSPO相的转变，以及Mg ₉₈ Zn ₁ Y ₁ -AC合金中的窄LPSO相，从而促进DRXed的形核谷物。 AC挤压显着提高了Mg-Zn-Y合金的强度。 AC挤压后，Mg _98.7 Zn ₁ Y _0.3合金的强度提高主要归因于细晶强化、位错强化和纳米相析出强化。经过AC处理后，更多的细晶粒和纳米相共同强化了Mg ₉₈ Zn ₁ Y ₁合金。 Mg ₉₈ Zn ₁ Y ₁合金在623 K挤压后获得最佳力学性能，极限拉伸强度(UTS)为406 MPa，屈服强度(YS)为388 MPa，延伸率(EL)为5.6%。