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

Abstract

Retrogression characteristics of a novel Al-Cu-Li-X alloy of 2A97 were studied by hardness testing, transmission electron microscopy (TEM), and differential scanning calorimetry (DSC). The retrogression treatments of aging at 155°C for 12 h followed by aging at 220 and 240°C were chosen by determining the peak temperature of δ' precipitation at 230°C by DSC. The retrogression treatment at a lower temperature of 220°C causes the precipitation and coarsening of δ' and θ' phases in the matrix, resulting in an increase in hardness. Retrogression at a higher temperature of 240°C causes the dissolution and coarsening of δ' and θ' precipitates in the matrix and on the grain boundaries, resulting in a decrease in hardness. Microstructural changes upon retrogression including the appearance of equilibrium precipitates such as T 1 , T 2 , δ', and θ are confirmed by the selected area electron diffraction and the bright and dark field image analysis.

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

“…Although laser beam welding of Al-Li alloy has been documented by a number of papers, most of them have been limited to certain types including 8090, 1420, 2090, etc. [6,7,[9][10][11][12], and up to now, many researches on 2A97 Al-Li alloy are primarily focused on the effects of heat treatments on the microstructure and mechanical properties [13,14]. Some information is available regarding friction stir welding of 2A97 [15,16], however, there are few reports published in the open literature on laser beam welding of 2A97 Al-Li alloy.…”