Maturation, Revenu et Réversion des alliages Al-Cu 4 %, Al-Cu-Mg et Al-Cu-Mg-Si de haute pureté

Precipitation in original Duralumin A-U4G versus modern 2017A alloy

“…Currently, 2017A contains some zinc whereas old version of this alloy does not. The ratios Mg:Si are 1.1 and 1.16 for 2017A and A-U4G, respectively, which correspond to reported values for Duralumin [7] .…”

“…This phase is expected at equilibrium state, in alloys of Mg/Si ratios lower than 1.73 [12] . Two years later, Saulnier and Syre [7] identified in a similar industrial Duralumin, thanks to electron microscopy (using oxide replicas), the presence of the so-called phase X (renamed '' later) after aging at 260 °C evolving into the '-Al 2 Cu phase at 290 °C, confirming the findings of Lambot. Another phase was evidenced with thermal dilatometry.…”

“…The microstructure of the A-U4G and 2017A in different states, asreceived and after artificial aging, will be reported hereafter by combining different techniques: conventional bright and dark field TEM, selected area diffraction patterns (SADP), scanning transmission electron microscopy coupled with energy dispersive X-ray spectroscopy (STEM-EDS), with high angle annular dark field (HAADF) imaging or with electron energy loss spectroscopy (EELS), differential scanning calorimetry (DSC) and small angle X-ray scattering (SAXS) experiments. It is shown that, compared to what could be expected from the literature on quaternary Al-Cu-Mg-Si alloys [15,16] with a range of 2.5-4.5 wt% of copper, and a ratio of Mg:Si close to 1 or what was observed in the 1950s and 1960s on Duralumin [7,13] , a complex and specific precipitation sequence occurs in these alloys.…”

“…In literature on Al-Cu-Mg-Si alloys, these peaks were attributed to different phases. It was first observed by Saulnier and Syre [7] that an exothermic peak at 290 °C coincided with the presence of the '-Al 2 Cu phase whereas the peak at 350 °C was marked by the apparition of a needle shape precipitation, supposedly Mg 2 Si. More recent works [20][21][22] report a peak around 250 °C as the growth of the quaternary (Q' or ')-AlCuMgSi phase and a peak around 280 °C as the apparition of the '-Al 2 Cu phase.…”

“…The discovery of coherent copper-rich zones in the Al-Cu 4% alloy was achieved independently by Guinier [5] and Preston [6] with X-ray experiments in 1938. It took even longer to be able to observe directly the nanoprecipitates responsible for the hardening: first observations were made on oxide replicas in France in 1952 by Saulnier and Syre [7] .…”