Crystallographic relationships of T-/S-phase aggregates in an Al–Cu–Mg–Ag alloy. (March 2019)

• Record Type: Journal Article
• Authors: Sunde, Jonas K.; Johnstone, Duncan N.; Wenner, Sigurd; van Helvoort, Antonius T.J.; Midgley, Paul A.; Holmestad, Randi
• Is Part Of: Acta materialia. Volume 166(2019)
• Page Start: 587
• Page End: 596
• Publication Date: 2019-03
• Subjects: Aluminium alloy -- Orientation relationships -- Dispersoid-precipitate aggregate -- ACOM-TEM -- Scanning precession electron diffraction; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2018.12.036
• Languages: English
• ISSNs: 1359-6454

Abstract

Abstract: T-(Al20 Cu2 Mn3 ) phase dispersoids are important for limiting recovery and controlling grain growth in Al-Cu alloys. However, these dispersoids can also reduce precipitation hardening by acting as heterogeneous nucleation sites and may lead to increased susceptibility towards pitting corrosion when galvanically coupled with S-(Al2 CuMg) phase precipitates. The interplay between T- and S-phases is therefore important for understanding their effect on the mechanical and electrochemical properties of Al-Cu-Mg alloys. Here, the crystallographic relationships between the T-phase, S-phase, and surrounding Al matrix were investigated in an Al-1.31Cu-1.14Mg-0.13Ag-0.10Fe-0.28Mn (at.%) alloy by combining scanning precession electron diffraction with misorientation analysis in 3-dimensional axis-angle space and high-resolution transmission electron microscopy. Orientation relationships are identified between all three phases, revealing S-T orientation relationships for the first time. Differences in S-Al orientation relationships for precipitates formed at T-phase interfaces compared to their non-interfacial counterparts were also identified. These insights provide a comprehensive assessment of the crystallographic relationships in T-/S-phase aggregates, which may guide future alloy design. Graphical abstract: Image 1