ABSTRACT In the present investigation, the effects of alloying elements (Sn, Pb) and grain refiner (Ag, Zr) on microstructure, mechanical and wear properties of as-cast Mg-Al-Zn alloys were studied. The alloys were prepared through melting-casting route under a protective atmosphere and cast into a permanent mould. The microstructure of the base alloy consisted of α-Mg, Mg17Al12 continuous eutectic phase at the grain boundary and Mg-Zn phase was distributed within the grains. Addition of Sn and Pb suppressed the formation of continuous Mg17Al12 eutectic phase and formed Pb enriched Mg2Sn precipitates at the grain boundary as well as inside the grain. The Ag and Zr addition to Mg-Al-Zn-Sn-Pb alloy suppressed the Mg17Al12 phase formation and refined the grains leading to improve mechanical properties. Addition of Sn, Pb and grain refiner (Ag, Zr) significantly enhanced the tensile strength and elongation but reduced hardness. The Ag addition imparted best tensile properties, where ultimate tensile strength (UTS) and elongation are 205 MPa and 8.0%, respectively. The fracture surfaces were examined under SEM which revealed cleavage facets and dimple formation. Therefore, the cleavage fracture and dimple rupture were considered as the dominant fracture mechanisms for developed Mg alloys. The cumulative volume loss of Mg alloys increased with sliding distance and applied load. The coefficient of friction decreased with sliding distance. The microscopic observation, analysis of the wear surface and coefficient of friction revealed that the wear mechanism of developed Mg alloys changes from abrasion oxidation to delamination wear.

中文翻译：

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合金元素和晶粒细化剂对Mg-Al-Zn合金显微组织、力学性能和磨损性能的影响

摘要 在本研究中，研究了合金元素（Sn、Pb）和晶粒细化剂（Ag、Zr）对铸态 Mg-Al-Zn 合金的显微组织、机械和磨损性能的影响。在保护气氛下通过熔铸工艺制备合金并浇铸到永久模具中。基体合金的显微组织由α-Mg、Mg17Al12 连续共晶相在晶界组成，Mg-Zn 相分布在晶粒内。Sn 和 Pb 的添加抑制了连续 Mg17Al12 共晶相的形成，并在晶界和晶粒内部形成了富含 Pb 的 Mg2Sn 析出物。添加到 Mg-Al-Zn-Sn-Pb 合金中的 Ag 和 Zr 抑制了 Mg17Al12 相的形成并细化了晶粒，从而提高了机械性能。添加 Sn、Pb 和晶粒细化剂（Ag、Zr) 显着提高了拉伸强度和伸长率，但降低了硬度。添加银赋予最佳拉伸性能，其中极限拉伸强度 (UTS) 和伸长率分别为 205 MPa 和 8.0%。在 SEM 下检查断裂表面，显示解理面和凹坑形成。因此，解理断裂和凹坑断裂被认为是开发镁合金的主要断裂机制。镁合金的累积体积损失随着滑动距离和施加载荷的增加而增加。摩擦系数随着滑动距离的增加而降低。显微观察、磨损表面和摩擦系数分析表明，发达镁合金的磨损机制由磨损氧化转变为分层磨损。