A new Mg-5Bi-1Mn-0.5Zn-0.2Ag (BMZQ5100, wt%) alloy is developed and analyzed comparatively its extrudability, microstructure, mechanical property and thermal stability with a commercial AZ91 alloy. The results show that the BMZQ5100 alloy can be successfully extruded at a high extrusion speed (ES) of 30 m/min without surface cracks, but there are a large number of hot cracks occurred on the low-speed-extruded AZ91 alloy surface (ES: 5 m/min). For the 30 m/min extruded BMZQ5100 alloy (BMZQ5100-E30), it exhibits a completely dynamic recrystallized (DRX) grain structure with a slightly larger grain size and stronger basal fiber texture than the 2 m/min extruded AZ91 alloy (AZ91-E2) without surface cracks. In terms of second phase, the former alloy contains submicron MgBi phases at grain boundaries (GBs), nano-scale MgBi and α-Mn particles within grain interiors, along with the co-segregation of Zn and Ag at GBs. The latter alloy has a continuous network of submicron MgAl phases along GBs, but no any solute segregation is observed at GBs. The BMZQ5100-E30 alloy exhibits more excellent mechanical properties with a tensile yield strength of ∼ 271 MPa, an ultimate tensile strength of ∼ 319 MPa and an acceptable elongation-to-failure of ∼ 8%, compared with the AZ91-E2 alloy. The GB strengthening, precipitation strengthening and solute segregation strengthening on the TYS occupy ∼ 46.2, ∼ 45.5 and ∼ 8.3%, respectively. In addition, the BMZQ5100-E30 alloy has higher microstructural thermal stability than the AZ91-E2 alloy, because of second phase pinning and solute segregation at GBs to effectively inhibit the grain growth during annealing.

中文翻译：

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开发比 AZ91 合金具有更高强度和微观结构热稳定性的高速挤压 BMZQ5100 合金

开发了一种新型Mg-5Bi-1Mn-0.5Zn-0.2Ag（BMZQ5100，wt%）合金，并与商用AZ91合金对其挤压性能、显微组织、力学性能和热稳定性进行了比较分析。结果表明，BMZQ5100合金可以在30 m/min的高挤压速度（ES）下成功挤压，且无表面裂纹，但低速挤压的AZ91合金表面出现大量热裂纹（ES）。 ：5 m/分钟）。对于30 m/min挤压的BMZQ5100合金（BMZQ5100-E30），它表现出完全动态再结晶（DRX）晶粒结构，与2 m/min挤压的AZ91合金（AZ91-E2）相比，晶粒尺寸稍大，基础纤维织构更强。 ）无表面裂纹。就第二相而言，前一种合金在晶界（GB）处含有亚微米MgBi相，晶粒内部含有纳米级MgBi和α-Mn颗粒，并且在晶界处存在Zn和Ag的共偏析。后一种合金沿着晶界具有连续的亚微米 MgAl 相网络，但在晶界处没有观察到任何溶质偏析。与 AZ91-E2 合金相比，BMZQ5100-E30 合金表现出更优异的机械性能，拉伸屈服强度为 ∼ 271 MPa，极限拉伸强度为 ∼ 319 MPa，可接受的断裂伸长率为 ∼ 8%。 TYS 上的晶界强化、沉淀强化和溶质偏析强化分别占~ 46.2、~ 45.5 和~ 8.3%。此外，BMZQ5100-E30合金比AZ91-E2合金具有更高的微观结构热稳定性，因为晶界处的第二相钉扎和溶质偏析有效抑制了退火过程中的晶粒长大。