The effect of heavy deformation on the precipitation in an Al-1.3Cu-1.0Mg-0.4Si wt.% alloy

• Published in: Materials & design Vol. 186; p. 108203
• Main Authors: Thronsen, Elisabeth, Marioara, Calin D., Sunde, Jonas K., Minakuchi, Kazuhiro, Katsumi, Tetsuya, Erga, Iven, Andersen, Sigmund J., Friis, Jesper, Marthinsen, Knut, Matsuda, Kenji, Holmestad, Randi
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15.01.2020; Elsevier
• Subjects: Al-Mg-Si-Cu alloys; High angle annular dark-field scanning transmission electron microscopy; Natural ageing; Pre-deformation; Precipitation; Scanning precession electron diffraction; Precipitation; High angle annular dark-field scanning transmission electron microscopy; Pre-deformation; Natural ageing; Scanning precession electron diffraction; Al-Mg-Si-Cu alloys
• ISSN: 0264-1275; 1873-4197
• DOI: 10.1016/j.matdes.2019.108203

This work has investigated the effect of the combination of natural ageing and 80% pre-deformation after solution heat treatment on precipitation during subsequent artificial ageing in an Al-1.3Cu-1.0Mg-0.4Si wt.% alloy. It was found that a combined use of atomic resolution aberration corrected high-angle annular dark-field scanning transmission electron microscopy and scanning precession electron diffraction enabled a detailed characterisation of precipitates in heavy pre-deformed materials. The dominant phase in the undeformed condition was the L phase. L was also found to be nucleated in the undistorted regions of the Al matrix in the pre-deformed conditions. Two phases with high aspect ratios were nucleated on dislocations: The C phase and a previously reported phase, which we named here the ‘E phase’. The crystal structure of E was solved experimentally as monoclinic with core composition Mg6Al2Si2Cu4, supported by density functional theory calculations. It was determined that the order of pre-deformation and natural ageing had an influence on the relative fractions of the aforementioned phases formed during artificial ageing. An increased fraction of C+E relative to L was found in the condition where the pre-deformation was applied after natural ageing as compared to the condition where the pre-deformation was applied before natural ageing. [Display omitted] •An advanced TEM for detailed characterisation of precipitates in pre-deformed materials is presented.•The effect of natural ageing and pre-deformation on precipitation in terms of type and distribution is investigated.•The crystal structure of a previously reported phase in pre-deformed Al-Mg-Si(-Cu) alloys is presented.