Nucleation and growth crystallography of Al8Mn5 on B2-Al(Mn,Fe) in AZ91
magnesium alloys
magnesium alloys
File(s)
Accepted version
Author(s)
Zeng, Guang
Xian, Jingwei
Gourlay, C
Type
Journal Article
Abstract
Manganese is widely added to Mg-Al-based alloys to form Al-(Mn,Fe) intermetallics that combat impurity Fe. Here EBSD, deep etching and FIB-tomography are combined to study the nucleation and growth crystallography of Al-Mn-Fe particles in Mg-9Al-0.7Zn-0.15Mn-0.002Fe (wt%) solidified at 1 K⋅s−1. It is shown that Al8Mn5 nucleates on B2-Al(Mn,Fe) particles and an incomplete peritectic transformation results in a Fe-richer B2-Al(Mn,Fe) core enveloped by a low-Fe Al8Mn5 shell. A reproducible orientation relationship (OR) is measured, and the close lattice match and OR are discussed in terms of the group-subgroup relationship between these phases. It is found that most rhombohedral Al8Mn5 particles are twinned, consisting of four orientations related by ∼90° rotations around three common , which is discussed in terms of the pseudo-cubic <100> axes of the Al8Mn5 rhombohedral gamma brass. Al8Mn5 grew as equiaxed particles that are explained by polyhedron models based on {100}, {110} and {112} facets of the pseudo-cubic Al8Mn5 cell. The results indicate that, at low Fe:Mn ratio, most impurity Fe is dissolved in B2 particles that are encapsulated by low-Fe Al8Mn5 which may be important for corrosion resistance.
Date Issued
2018-07-01
Date Acceptance
2018-04-13
Citation
Acta Materialia, 2018, 153, pp.364-376
ISSN
1359-6454
Publisher
Elsevier
Start Page
364
End Page
376
Journal / Book Title
Acta Materialia
Volume
153
Copyright Statement
© 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. This manuscript is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/
Sponsor
Engineering & Physical Science Research Council (EPSRC)
Grant Number
EP/M002241/1
Subjects
Science & Technology
Technology
Materials Science, Multidisciplinary
Metallurgy & Metallurgical Engineering
Materials Science
Electron backscatter diffraction
Intermetallics
Crystal growth
PERCENT AL-MN
ELECTRON BACKSCATTER DIFFRACTION
ALUMINUM-MANGANESE
PHASE-DIAGRAM
ZN ALLOYS
SOLIDIFICATION
PARTICLES
CORROSION
SYSTEM
MICROSTRUCTURE
0912 Materials Engineering
0913 Mechanical Engineering
Materials
Publication Status
Published
Date Publish Online
2018-04-17