There is a growing interest in the use of ionic liquids to provide lubrication for challenging contacts. This study is an initial assessment of the application of two ionic liquids based on choline chloride cations to be used as ionic liquid lubricants for engineering contacts, in this case steel on steel. These ionic liquids, termed ethaline and reline, have anions of ethylene glycol and urea, respectively, and are available at relatively low costs and in high quantities. In order to assess the lubrication performance of the ionic liquids, lubricated reciprocating sliding wear tests were conducted between M2 tool steel samples and a steel stylus. Initial tests conducted at a sliding speed of 0.005 m s -1 and 30 N showed that ionic liquids could provide low friction lubrication, comparable to that of SAE 5W30 friction modifier free engine oil under the same test conditions; however, lubrication was lost after short sliding distances. Further testing with higher sliding speed/lower load and varying sample surface textures showed that ionic liquid lubrication could be better maintained in high-speed/ low-load testing and by increasing the roughness and therefore surface area of the sample. It was also observed that the choline chloride/urea ionic liquid formed a residual film when tested on iron silicate peened samples, and that this film may promote lubrication.
The effect of Fe and Mn on the microstructure and mechanical properties of a series of Al-5wt.%Mg alloys processed by high pressure die casting (HPDC) was investigated. The Calculation of Phase Diagrams modelling (CALPHAD) was also carried out to understand the phase formation in experimental alloys. The results show that Fe can be a beneficial element in the Al-Mg and Al-Mg-Mn alloys to improve the mechanical properties. Fe only exists in the form of equilibrium Al13Fe4 phase in Al-Mg-Fe alloys. While, the addition of 0.6wt.%Mn suppresses the formation of equilibrium Al13Fe4 phase. In Al-Mg-Mn-Fe alloys, all Fe-rich intermetallics is Al6(Fe, Mn) phase when Fe level is less than 2.5wt.%. When further increasing the Fe level, the primary non-equilibrium Al6(Fe, Mn) phase gradually evolves to form equilibrium Al13Fe4 phase, but the eutectic phase is still Al6(Fe, Mn). It was also found that both the eutectic Al13Fe4 in Al-Mg-Fe alloys and eutectic Al6(Fe, Mn) in Al-Mg-Mn-Fe alloys are divorced in the eutectic phases as the primary Fe-rich phases appear. The Fe-rich intermetallic significantly affect the mechanical properties of experimental alloys. Fe enhances the yield strength obviously but reduces the elongation significantly. The ultimate tensile strength is also improved by Fe addition when Fe level is less than 2.0wt.%, but it is significantly decreased with further increasing the Fe level. Moreover, the Mn addition is found to increase the volume of strengthening Fe-rich intermetallic and thus can further strengthen Al-Mg alloys.
This work aims to reveal the valuable role of Zr in cast Al-Si-Cu-Mg alloys utilised at elevated temperatures. The Al7Si2Cu0.2Zr alloy, subjected to well-tuned heat treatment process, was benchmarked against the conventional Al7Si0.5Cu alloy. Microstructural investigation showed that the main strengthening phases in the Al7Si2Cu0.2Zr alloy are θ´, Q´, Al-Si-Cu-Zr and Al-Si-Zr precipitates. Two Zr-containing precipitates (Al-Si-Cu-Zr and Al-Si-Zr) with the size of 80-200 nm are formed during solutionising at530 °C, which can be considered as the first ageing step. Other two Cu-containing precipitates (θ´and Q´) at the size of 20 nm are formed during ageing (170 °C). Nano-sized Zr-containing precipitates are mostly exhibited elliptical morphology with coherent/semi-coherent interfaces with the α-Al matrix, making them more stable at elevated temperatures. As a result, the yield strength is improved at room temperature from 261 to 291 MPa, and the ultimate tensile strength (UTS) is improved from 282 to 335 MPa for the Al7Si2Cu0.2Zr alloy, compared with the Al7Si0.5Cu alloy. Moreover, the mechanical properties are significantly improved at elevated temperatures. The yield strength and UTS at 200 °C are 177 and 186 MPa, respectively, for the Al7Si0.5Cu alloy. But these are224 and 246 MPa, respectively, for the Al7Si2Cu0.2Zr 2 alloy. The improvement of mechanical properties at elevated temperatures is mainly attributed to the refined microstructure and the precipitation of strengthening phases containing slow-diffused Zr element to retard the precipitation coarsening. Furthermore, the addition of Cu changes the precipitates from θ´ and β´´ in the Al7Si0.5Cu alloy to θ´ and Q´ in the Al7Si2Cu0.2Zr alloy which, in turn, induce a complementary effect on the improvement of mechanical properties.
The Zr-modified Al-Si-Cu-Mg alloy with 0.14wt%Zr addition was studied against the counterparts of commercially used EN-AC-42000 (Al7Si0.5Cu) baseline alloy for the effect of Zr on the high cycle fatigue (HCF) and mechanical properties at elevated temperatures of 150, 200, 250 o C. It was found that the fatigue life was significantly improved by 8-10 times at the high stress amplitude of 140 MPa in the Zr-modified alloy at all different temperatures. The
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.