Effect of lithium on mechanical and corrosion properties of friction stir back extruded Al-Cu-Mg alloy

Abstract

In this study, the effect of severe plastic deformation during friction stir back extrusion of Al-Cu-Mg alloy with different amounts of Li microalloying on microstructure, mechanical properties, and corrosion resistance was investigated. The Cu:Mg ratio in the Al-Cu-Mg alloy was 3.8. The results show that regardless of the amount of lithium microalloying added in the Al-Cu-Mg alloy, a significant change in the size of the dendrites, as well as the amount of secondary phase particles, and the eutectic structure formed in the inter-dendritic space, is not visible. Although with the increase of lithium percentage up to 0.5 wt.%, a slight decrease in grain size is observed in the central area and surface areas of the extruded wires, the difference in the average grain size in the three samples is not large. As the amount of lithium increases, the amount of lithium in the structure of S-Al2CuMg precipitates increases, and finer precipices are formed. By adding 0.5 wt.% of lithium, the evidence shows that the corrosion resistance has increased by 35 %. It is also observed that the corrosion potential decreases by 7 % with the increase of lithium percentage up to 0.5 wt.%.

Effect of Mn/Ag Ratio on Microstructure and Mechanical Properties of Heat-Resistant Al-Cu Alloys

“…This could be attributed to the segregation of Ag and Mn atoms at the Al/θ′-Al 2 Cu interface. Specifically, phase field simulations have suggested the synergistic roles of thermodynamic and kinetics effects in retarding the coarsening of θ′-Al 2 Cu precipitates [ 66 , 67 , 68 ]. In the thermodynamics aspect, the θ′-Al 2 Cu particles possess a plate-like morphology in the Al matrix with a coherent (001) Al ||(001) θ′ interface along the broad faces and a semi-coherent (001) Al ||(001) θ′ interface at the periphery of the plate.…”