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- Banijamali, S. M., et al.
(författare)
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Effect of Ce Addition on the Tribological Behavior of ZK60 Mg-Alloy
- 2021
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Ingår i: Metals and Materials International. - : Springer. - 1598-9623 .- 2005-4149. ; 27:8, s. 2732-2742
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Tidskriftsartikel (refereegranskat)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.
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| 2. |
- Najafi, Soroush, et al.
(författare)
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The Effect of Y Addition on the Microstructure and Work Hardening Behavior of Mg-Zn-Zr Alloys
- 2021
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Ingår i: Journal of materials engineering and performance (Print). - : Springer. - 1059-9495 .- 1544-1024. ; 30:4, s. 2574-2585
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Tidskriftsartikel (refereegranskat)abstract
- The effect of adding different amounts of Y on the microstructure, mechanical properties, texture and work hardening behavior of the extruded Mg-6Zn-0.5Zr-xY alloys (x = 0, 1, 2, 3 wt.%) was investigated. According to the results, the microstructure of all alloys is composed of α-Mg grains and Mg7Zn3 particles. By adding Y, in addition to grain refinement, Mg24Y5 and Mg3Y2Zn3 particles are formed in the microstructure. Among the alloys studied, the ZK60-3Y alloy has the highest strengths, as the yield stress and ultimate tensile strength of 318 and 366 MPa, respectively, were obtained for that alloy. This is due to the finer grains and higher volume fraction of the particles in the ZK60-3Y alloy. Meanwhile, reducing the grain size by Y addition affects the work hardening behavior; Y addition reduces the saturation stress, hardening capacity, and work hardening exponent by increasing the dynamic recovery; i.e., the more Y is added, the greater is the drop in the work hardening parameters. The effects of Y addition on work hardening behavior and dynamic recovery were investigated by examining microstructural developments, the volume fraction of particles and texture evaluation. The results of the texture evaluations showed that the addition of Y changes the texture component and intensity of the basal planes and can cause work hardening loss by activating slip on the non-basal planes.
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