Portal de Periódicos da CAPES

The effect of minor solute additions on the precipitation path of an Al Cu Li alloy

2016; Elsevier BV; Volume: 115; Linguagem: Inglês

10.1016/j.actamat.2016.05.050

1873-2453

Eva Gumbmann, Williams Lefebvre, Frédéric De Geuser, Christophe Sigli, A. Deschamps,

Magnesium Alloys: Properties and Applications

Minor solute additions of Mg, Ag or Zn to AlCuLi alloys are known to promote the formation of the T1-Al2CuLi phase and improve the strengthening of these alloys. In this paper, we use atomic resolution high angle annular dark field scanning transmission electron microscopy (STEM-HAADF) in conjunction with electron dispersive spectroscopy (EDS) mapping to elucidate the mechanisms by which these minor solute additions modify the precipitation path. The results show that the presence of Mg profoundly changes the nature of the precipitates formed, as early as the nucleation stage. In the presence of Mg, precursor phases containing Mg and Cu form at the dislocations, and later lead to a microstructure with GPB zones and S phase together with a high number density of T1 precipitates. In the absence of Mg, GPI zones form in the early stages of precipitation and later lead to a microstructure dominated by θ′ precipitates, with a low density of T1. Ag and Zn additions do not change the precipitation sequence, yet they are found in the T1 precipitates, Ag located at the precipitate/matrix interface, and Zn within the precipitate, probably substituting for Cu.