Direct observation of beta″ precipitate with a three-dimensional periodic structure in binary Mg–La alloy. (5th November 2019)

• Record Type: Journal Article
• Authors: Sun, Benzhe; Dong, Yu; Tan, Jun; Zhang, Haixiao; Sun, Yonghui
• Is Part Of: Materials & design. Volume 181(2019)
• Publication Date: 2019-11-05
• Subjects: Magnesium alloy -- Scanning transmission electron microscopy -- Metastable precipitate -- Three-dimensional periodic structure -- Stacking fault; Materials -- Periodicals; Engineering design -- Periodicals; Matériaux -- Périodiques; Conception technique -- Périodiques; Electronic journals; 620.11
• DOI: 10.1016/j.matdes.2019.107939
• Languages: English
• ISSNs: 0264-1275

Abstract

Abstract: It is a long-debated issue whether or not β ′′ forms in magnesium-rare earth alloys. In this study, after solid solution and aging treatment, the binary Mg-3.0 wt% La alloys were characterized using atomic-resolution scanning transmission electron microscopy. A large number of β ′′ metastable precipitate was captured successfully along [0001]α and 11 2 ¯ 0 α directions. The [0001]α observation reveals that the inchoate β ′′ is composed of single row of linked hexagonal rings. Under further aging, the expansion direction of the hexagonal ring is not limited to 11 2 ¯ 0 α direction and the β ′′ can reach a thickness of 5 c β ′′ along [0001]α, demonstrating that the β ′′ forms a three-dimensional periodic structure and the β ′′ phase can form in binary MgLa alloy. Meanwhile, a planar defect with an ABCBA stacking fault can be formed usually in the interface between β ′′ phase and α-Mg matrix, which contributes to alleviate the distortion of adjacent α-Mg matrix. Graphical abstract: Along [0001] α and 11 2 ¯ 0 α directions, the direct imaging of the β ′′ reveals that the β ′′ is characteristic of a three-dimensional periodic structure and the β ′′ phase can form in binary MgLa alloy.Unlabelled Image Highlights: A large number of β ′′ precipitate was observed in MgLa alloy by atomic-resolution STEM. The β ′′ precipitate with a three-dimensional periodic structure can form in MgLa alloy. An ABCBA stacking fault can be formed in the interface between β ′′ phase and α-Mg matrix.