Formation of giant atomic clusters in the β-Samson (β-Al3Mg2) phase of the Al-Mg alloy system. (15th April 2017)

• Record Type: Journal Article
• Authors: Nakayama, Kei; Tsuruta, Hijiri; Koyama, Yasumasa
• Is Part Of: Acta materialia. Volume 128(2017)
• Page Start: 249
• Page End: 257
• Publication Date: 2017-04-15
• Subjects: MgAl alloys -- Intermetallic compounds -- Samson cluster -- Transmission electron microscopy; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2017.02.019
• Languages: English
• ISSNs: 1359-6454

Abstract

Abstract: The crystallographic features of the (α-Mn → α-Mn + β-Samson) reaction in Al-Mg alloys around the composition of 48 at.% Mg have been investigated mainly by transmission electron microscopy to understand the formation of giant atomic clusters in the β-Samson structure. It was confirmed, for instance, that the state of an Al-48 at.% Mg alloy annealed at 573 K for 24 h could be identified as the (α-Mn + β-Samson) coexistence state, and that metastable states were found locally in α-Mn/β-Samson boundary regions. An analysis of electron diffraction patterns obtained from the coexistence state indicated that the orientation relationship of ( 3 ¯ 30)α //( 8 ¯ 80)β-S and [110]α //[110]β-S was established between α-Mn and β-Samson regions, together with a lattice contraction of about 10% along the [001]α direction and an expansion of about 0.4% along the [ 1 ¯ 10]α direction in the (α-Mn → β-Samson) structural change. High-resolution electron micrographs of the coexistence state also suggested that some atoms at the Mg (I) and Mg (II) sites in the distorted α-Mn structure could be converted to those at the Mg (23) site of the β-Samson structure as the center site of the Samson cluster. Furthermore, both the features of giant clusters in the β-Samson structure and their formation from the α-Mn structure were discussed on the basis of the experimental data obtained in this study. Graphical abstract: Image 1