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Effect of Ce Addition on the Tribological Behavior of ZK60 Mg-Alloy
Metals and Materials International ( IF 3.5 ) Pub Date : 2020-08-06 , DOI: 10.1007/s12540-020-00832-4
S. M. Banijamali , Y. Palizdar , S. Najafi , A. Sheikhani , M. Soltan Ali Nezhad , P. Valizadeh Moghaddam , H. Torkamani

Abstract

The present work aims to study the tribological behavior of an extruded ZK60 alloy in the presence of Ce; in a previous study, among ZK60 alloys with different Ce addition rates, an alloy with 3 wt% of Ce was found to exhibit the most promising mechanical (e.g., hardness and strengths) properties, while its wear behavior remained unknown. The results of microstructural examinations by optical and electron microscopes show that Ce addition reduces the grain size from 6.1 to 2.0 μm. Besides, in addition to the precipitates already distributed in the base alloy (Mg7Zn3), Ce could promote the formation of a new precipitate (MgZn2Ce), increasing the total fraction of the precipitates. These microstructural evolutions enhance the strengths of the studied ZK60 alloy, as the yield and tensile strengths increase from 212 to 308 MPa and from 297 to 354 MPa, respectively. A pin on disc tribometer was employed to study the wear behavior of the developed alloy under different normal loads (5, 20, 40, and 60 N). The results show that the base and Ce-added alloys exhibit almost a similar frictional behavior, while the wear resistance of the Ce-added alloy is higher within the load ranges applied: (i) in low load conditions (5 and 20 N), where the abrasive wear is the active mechanism, the precipitates in the Ce-added alloy could enhance the wear resistance. (ii) Under the load of 40 N, oxidative wear is also an operative wear mechanism, leading to a sharp increase in the wear rate of the alloys. In this condition, Ce could provide a protective oxide layer, which could improve the wear resistance of the alloy. (iii) At a load of 60 N, both studied alloys exhibit a similar wear rate due to a severe oxidation condition. Therefore, beyond this loading condition, the microstructural evolutions (e.g., change in precipitation behavior) caused by Ce addition can no longer contribute to the enhancement of wear resistance.

Graphic Abstract



中文翻译:

铈对ZK60镁合金摩擦学行为的影响

摘要

本工作旨在研究在存在Ce的情况下挤压ZK60合金的摩擦学行为。在先前的研究中,在添加不同Ce的ZK60合金中,发现Ce含量为3 wt%的合金表现出最有希望的机械性能(例如硬度和强度),而其磨损行为仍然未知。光学和电子显微镜的显微结构检查结果表明,铈的添加将晶粒尺寸从6.1微米减小到2.0微米。此外,除了已经分布在基体合金(Mg 7 Zn 3)中的析出物外,铈还可以促进新的析出物(MgZn 2)的形成。Ce),增加沉淀物的总含量。随着屈服强度和拉伸强度分别从212 MPa升高到308 MPa和从297 MPa升高到354 MPa,这些微观结构的演变增强了所研究ZK60合金的强度。盘式摩擦计上的销钉用于研究已开发的合金在不同法向载荷(5、20、40和60 N)下的磨损行为。结果表明,基体合金和添加铈的合金表现出几乎相似的摩擦性能,而添加铈的合金的耐磨性在所施加的载荷范围内更高:(i)在低载荷条件(5和20 N)下,在磨料磨损是其主要作用机理的情况下,添加铈的合金中的析出物可以提高耐磨性。(ii)在40 N的负载下,氧化磨损也是一种有效的磨损机制,导致合金的磨损率急剧增加。在这种条件下,铈可以提供保护性氧化层,从而可以提高合金的耐磨性。(iii)在60 N的载荷下,两种研究的合金由于严重的氧化条件而表现出相似的磨损率。因此,超过此加载条件,由于添加铈引起的微观结构演变(例如,析出行为的变化)将不再有助​​于增强耐磨性。

图形摘要

更新日期:2020-08-06
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