article · Alexandria Engineering Journal
Equal channel angular pressing at room temperature was applied to an AA7075 aluminium alloy for up to six passes to investigate changes in microstructure, hardness, and dry sliding wear behaviour. Successive passes refined the alloy grain structure, generated high-density dislocations, dispersed nanoparticles, and progressively enhanced microhardness up to 223 HV at six passes. Morphological evaluation revealed a shift in the primary wear mechanisms. Untreated samples exhibited delamination, adhesion, and plastic deformation, which transformed into ploughing bands at five passes and abrasive wear after six passes, while oxidation affected all specimens. Although the coefficient of friction rose with more passes as the lubricating effect of delamination debris diminished, the wear rate declined because of the substantial matrix hardening. These findings established an inverse relationship between the friction coefficient and wear rate in the processed alloy.
Understanding how severe plastic deformation alters the mechanical properties of aluminium alloys enables better prediction of surface degradation. Demonstrating that increased matrix hardness reduces overall material loss, despite an increase in friction, gives engineers useful criteria for evaluating structural alloys subject to dry sliding contact.
This early-stage research provides material property data that could inform developers and metallurgists working on high-strength aluminium components subjected to sliding contact. However, the abstract does not indicate an explicit commercial application pathway, presenting only laboratory-scale testing and microstructural analysis.
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Equal channel angular pressing (ECAP) of AA7075 alloy, at room temperature, with six numbers of passes, has been successfully processed. Microstructure observations, microhardness experiment, wear test, and worn surface morphology examination were performed to investigate the increasing passes number’s effect on wear behaviors. Increasing the number of passes leads to the observation of refined grains, high-density dislocations, dispersed nanoparticles, and continuous improvement of microhardness to 223 HV at six passes. The SEM results of the specimens after the wear test showed that delamination, plastic deformation, and adhesion mechanism were dominated wear mechanisms in the before-ECAP sample. However, with the increased pass number, the delamination gradually transformed into the ploughing bands, which were the dominant wear mechanism in 5 passes because of the hardened aluminum matrix. After six passes of ECAP, the abrasion wear was founded to start work as a significantly important wear mechanism. Besides, the oxidation plays a remarkable role in the wear mechanism in all the tested samples. The coefficient of friction increased as the increase of passes number due to the deceased lubricant effect acted by delamination, which was gradual shrank from aggregation to debris. Nevertheless, the wear rate decreased with the increased passes number owing to the low applied wear load and increased hardness after ECAP. Based on the study of the inverse correlation between the coefficient of friction and the wear rate, a relation between them was introduced for the ECAPed aluminum alloy.
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DOI: 10.1016/j.aej.2020.10.021
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