Two types of S phase precipitates in Al–Cu–Mg alloys

• Published in: Acta materialia Vol. 55; no. 3; pp. 933 - 941
• Main Authors: Wang, S.C., Starink, M.J.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-02-2007; Elsevier Science
• Subjects: Al–Cu–Mg alloy; Applied sciences; DSC; Exact sciences and technology; Metals. Metallurgy; Orientation relationship; S precipitate; TEM; S precipitate; Orientation relationship; Al–Cu–Mg alloy; DSC; TEM; Differential scanning calorimetry; Precipitation; Transmission electron microscopy; Precipitate; Al-Cu-Mg alloy; Copper alloy
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2006.09.015

Transmission electron microscopy (TEM) and differential scanning calorimetry (DSC) have been used to study S phase precipitation in an Al–4.2 Cu–1.5 Mg–0.6 Mn–0.5 Si (AA2024) and an Al–4.2 Cu–1.5 Mg–0.6 Mn–0.08 Si (AA2324) (wt.%) alloy. In DSC experiments on as solution treated samples two distinct exothermic peaks are observed in the range 250–350°C, whereas only one peak is observed in solution treated and subsequently stretched or cold worked samples. Samples heated to 270 and 400°C at a rate of 10°C/min in the DSC have been studied by TEM. The selected area diffraction patterns show that S phase precipitates with the classic orientation relationship form during the lower temperature peak, and for the solution treated samples, the higher temperature peak is caused by the formation of a second type of S phase precipitates which has an orientation relationship that is rotated by ∼4° to the classic one. The effects of Si and cold work on the formation of the second type of S precipitates have been discussed.