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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
Highlights
Magnesium alloys have attracted considerable attention due to their high specific buckling resistance, good castability, low density, and good damping capacity, making them suitable for some applications such as automotive industries, aircraft structures, and other lightweight structural components [1]
The results of grain size measurement show that the grain size of ZK60 alloy is reduced from 6.1 to 2.0 μm when 3 wt% of Ce has been added to the base alloy
This study investigated the effect of Ce addition (3 wt%) on the wear behavior of ZK60 extruded alloy under different normal loads
Summary
Magnesium alloys have attracted considerable attention due to their high specific buckling resistance, good castability, low density, and good damping capacity, making them suitable for some applications such as automotive industries, aircraft structures, and other lightweight structural components [1] Their relatively low strength and weak tribological behavior have limited the potential applications of these alloys. It has been reported elsewhere that the tensile behavior of Mg–Zn–Zr alloy is significantly improved by RE addition (Y and Ce), which is due to the grain refinement and formation of different intermetallic phases [12, 15]. It has been reported elsewhere that the addition of Ce-rich misch metal to AZ91 alloy results in the formation of an intermetallic phase, leading to enhancement of high temperature creep resistance and wear behavior of the alloy tested against a tool steel. Attempts have been made to unveil the link between the microstructural features and wear property in the developed Ce-added alloy
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