Effects of RRA Treatments on Microstructures and Properties of a New High-strength Aluminum-Lithium Alloy-2A97

Retrogression characteristics of a novel Al-Cu-Li-X alloy

“…At 220°C, the rate of precipitation and coarsening of δ' phase is greater than the dissolution rate, but it is adversely different from that at 240°C. This has been confirmed by the response of tensile properties to the retrogression treatment, which shows a higher strength at a lower temperature [14]. In the present experiment, a higher retrogression treatment temperature is employed, and a larger drop in hardness occurs.…”

“…The endothermic effect shows that the dissolution temperature of δ' phase ranges from 195.4 to 249.9°C with an endothermic peak temperature at 230°C [14]. Based on this result, retrogression temperatures were chosen at 220 and 240°C, at which the precipitation and coarsening of δ' phase occurs accompanied by the dissolution of δ' phase during high-temperature retrogression treatment [15][16][17].…”

“…When the retrogressed alloy was reaged at high temperature, the restoration of strength and ductility occurred because of the reprecipitation of δ' phase in the matrix and the resegregation of lithium on grain boundaries. Since the coherent ordered dispersoids of δ' in 2A97 alloy are prone to dissolve into the matrix, the effect of retrogression and reaging treatment on the microstructures and properties was investigated [14]. In this work, the microstructural changes and hardness evolutions during retrogression treatment in the high-strength 2A97 alloy were identified.…”

Microstructure and mechanical properties of newly developed aluminum–lithium alloy 2A97 welded by fiber laser

“…The endothermic peak A corresponds to the partial dissolution of δ 0 and GP zones, and the exothermic peak B has resulted from the precipitation of GP zones, δ 0 and θ″, the second endothermic peak C is ascribed to the dissolution of residual δ 0 and GP zones or other precipitates formed during the DSC scan, the second and third exothermic peaks D and E are due to the precipitation and growth of T 1 , T 2 , θ 0 , δ, etc. Finally, a wide dissolution peak F of all the precipitates forms [28]. The DSC curve for FZ is less fluctuant than that of BM with decreasing reaction enthalpies for all the thermic effects, which clearly indicates the reduction of precipitates after laser beam welding and a weak ability of re-precipitation due to solute segregation.…”

Influence of Pre-deformation on Aging Precipitation Behavior of Three Al–Cu–Li Alloys

“…Most references contributed the strength enhancement to the refinement of T1 precipitates caused by plastic deformation prior to artificial aging. The plastic deformation introduces dislocations into the matrix, which act as preferential matrix nucleation sites of strengthening precipitate T1 [12][13][14][15][16][17][18]. Increasing the amount of introduced plastic deformation leads to a greater number of matrix dislocations, and therefore increases the population density of T1 precipitates and decreases their size [19,20].…”