Atomic-scale investigation of the heterogeneous precipitation in the E (Al18Mg3Cr2) dispersoid of 7075 aluminum alloy

JOURNAL OF ALLOYS AND COMPOUNDS

卷:851

Article

Ding, Lipeng^1,2,3  Zhao, Lv⁴  Weng, Yaoyao⁵  Schryvers, Dominique³  Liu, Qing¹  Idrissi, Hosni^2,3 

[1] Nanjing Tech Univ, Key Lab Light Weight Mat, Nanjing 211816, Peoples R China

[2] UCLouvain, Inst Mech Mat & Civil Engn, IMAP, B-1348 Louvain La Neuve, Belgium

[3] Univ Antwerp, Dept Phys, Electron Microscopy Mat Sci EMAT, Groenenborgerlaan 171 B, B-2020 Antwerp, Belgium

[4] Huazhong Univ Sci & Technol, Dept Mech, Wuhan, Peoples R China

[5] Nanjing Inst Technol, Sch Mat Sci & Engn, Nanjing 211167, Peoples R China

关键词: Aluminum alloys;    Heterogeneous precipitation;    Dispersoid;    HAADF-STEM;   

DOI  :  10.1016/j.jallcom.2020.156890

来源: Elsevier

【 摘 要 】

The heterogeneous precipitation of the eta (MgZn2) phase on the E (Al18Mg3Cr2) dispersoids of the 7075 aluminum alloy was systematically investigated by atomic resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and energy dispersive X-ray spectrometry (EDX). It is found that coarse B particles are heterogeneously precipitated at the E particle interface after water quenching and isothermal aging at 120 degrees C. The incoherent E/Al interface is responsible for the high tendency of heterogeneous precipitation of the B phase. Two different orientation relationships (ORs) between the eta, E and Al matrix are identified: OR1 [2 (11) over bar0](eta)[011](E)//[(1) over bar 12](Al), (01 (1) over bar0)(eta)//(13 (3) over bar)(E)//(201)(Al), OR2 [(1) over bar 12](E)//[0001](eta)//[011](Al), (01 (1) over bar0 )(eta)//(220)(E)//(34 (4) over bar)(Al). The eta phase is preferential to nucleate along the {111}(E) or the {220}(E) planes, depending on its OR. The heterogeneous nucleation of B phase on the E particle could stabilize the E/Al interface by introducing a coherent E/eta interface, which increases the drive force of heterogeneous precipitation. The reorientation of eta phase and mutual diffusion of solute atoms could assist the coherency of the E/eta interface. The present results suggest that increasing the coherency of the E/Al interface is a promising method to suppress the heterogeneous precipitation of the eta phase. (C) 2020 Elsevier B.V. All rights reserved.

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