Particle induced visible light absorption enhancement on Al–Cu–Mg alloy fatigue fracture surfaces

Junfeng Zhao,Wenwen Liu,Dandan Shi,Xianli Shi,Caiqiong Li,Han Dai,Xiaoyan Dong,Wencheng Song,Xinxiang Yu

doi:10.1063/5.0074130

Junfeng Zhao, Wenwen Liu + Show 7 more

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https://doi.org/10.1063/5.0074130

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Abstract

Particle induced visible light absorption enhancement on Al–Cu–Mg alloy fatigue fracture surfaces has been studied. By the calculations of three possible structures in optical dark areas (ODAs) in Al–Cu–Mg alloys, the light absorption abilities of Cu nanoparticles and Cu/Al2O3 particles are clearly revealed. Based on the calculations, the formation mechanism of ODA can be mainly attributed to the formation of Cu nanoparticles and Cu/Al2O3 particles, which lead to strong light absorption enhancement in the visible spectrum. In detail, Cu nanoparticles with larger radii exhibit higher light absorption. In addition, the formation of Cu/Al2O3 particles can further enhance the light absorption of Cu nanoparticles in ODA, which coincide well with the experimental results. The cathodic protection method is proved as an efficient way for avoiding the formation of ODA, and thus, the fatigue life of Al–Cu–Mg alloys is also greatly improved. This work should provide deeper insights into the formation mechanism of ODA in Al–Cu–Mg and other Cu contained Al alloys with high-cycle loadings.

Highlights

Al–Cu–Mg alloys in engineering are mainly used in the condition of cyclic loading owing to their application in fuselage constructions, truck hubs, propeller components, etc.1 Notably, optical dark areas (ODAs) found in the fatigue fracture surfaces of Al–Cu–Mg alloys under high-cycle loadings (105–107), especially in the 2024-T3 Al alloy, have been troubling the engineering fields for many years.2 Generally, the formation mechanisms of ODA in Al–Cu–Mg alloys are mainly transplanted from that in the steels, such as decohesion of spherical carbides,3 hydrogen-assisted crack growth,4 and formation and debonding of fine granular layers.5 Obviously, there are huge differences, such as chemical activity and strength, microstructure, between Al alloys and steels
The light absorption of three most possible structures in Al–Cu–Mg alloys, Cu layers with various thicknesses adhered to the Al2O3/Al flat substrate, Cu nanoparticles with various radius adhered to Al2O3/Al flat substrate, and Cu/Al2O3 mixed particles with various radii, have been calculated
The light absorption enhancement in ODA caused by the high roughness of the fatigue fracture surfaces can be ignored it will lead to multiple light absorption

Summary

INTRODUCTION

Al–Cu–Mg alloys in engineering are mainly used in the condition of cyclic loading owing to their application in fuselage constructions, truck hubs, propeller components, etc. Notably, optical dark areas (ODAs) found in the fatigue fracture surfaces of Al–Cu–Mg alloys under high-cycle loadings (105–107), especially in the 2024-T3 Al alloy, have been troubling the engineering fields for many years. Generally, the formation mechanisms of ODA in Al–Cu–Mg alloys are mainly transplanted from that in the steels, such as decohesion of spherical carbides, hydrogen-assisted crack growth, and formation and debonding of fine granular layers. Obviously, there are huge differences, such as chemical activity and strength, microstructure, between Al alloys and steels. Many distinctive phenomena in Al–Cu–Mg alloys, such as no carbon and the formation of mixed Cu, Al2O3, and MgO nano/microparticles in ODA, have no clear explanations yet.. It is well known that the radius and surrounding-medium refractive index of metal nanoparticles have significant influences on their absorption abilities.10–12 Many of these factors such as the radius of Cu nanoparticles, the influences of Al2O3 and MgO mixed nano/microparticles, and the natural oxide layer of Al2O3 to the actual light absorption capacity in ODA have not been studied yet. The light absorption of three most possible structures in Al–Cu–Mg alloys, Cu layers with various thicknesses adhered to the Al2O3/Al flat substrate, Cu nanoparticles with various radius adhered to Al2O3/Al flat substrate, and Cu/Al2O3 mixed particles with various radii, have been calculated. A cathodic protection method has been carried out to avoid the formation of mixed nano/microparticles, thereby successfully preventing the formation of ODA in Al–Cu–Mg alloys

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RESULTS AND DISCUSSION

CONCLUSION