Abstract
The dendritic morphologies of hot-dip galvanized Zn-0.2 wt pct Al coatings on steel sheets with two different surface roughness conditions were systematically examined as functions of the inclination angle and axis of the Zn basal plane with respect to the sheet surface by using electron backscattered diffraction. When the inclination axis of the basal plane was ⟨ 1 2 ¯ 10 ⟩ , the dendrite changed its morphology by following the sequence of six-fold → eight-fold → elongated X → elongated X + C patterns with increasing inclination angle. When the inclination axis was ⟨ 10 1 ¯ 0 ⟩ , the sequence of morphological patterns on the mirror-polished steel substrate was six-fold → eight-fold → two-fold → four-fold, whereas, for the steel substrate with a rough surface, the eight-fold pattern was missing in the sequence. These sequences of morphological changes indicated the presence of a third family of preferred dendritic growth directions, in addition to the two previously known families of ⟨ 10 1 ¯ 0 ⟩ and ⟨ 0001 ⟩. The third growth direction family is proposed to be those normal to the { 1 2 ¯ 11 } planes. The absence of the eight-fold pattern on the rough steel surface was attributed to the surface undulation that perturbed the growth in the six weakly preferred directions toward the two strongly preferred ⟨ 10 1 ¯ 0 ⟩ directions.
Original language | English |
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Pages (from-to) | 3186-3200 |
Number of pages | 15 |
Journal | Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science |
Volume | 50 |
Issue number | 7 |
DOIs | |
Publication status | Published - 2019 Jul 15 |
Bibliographical note
Funding Information:The authors are grateful for the technical and financial supports by POSCO.
Publisher Copyright:
© 2019, The Minerals, Metals & Materials Society and ASM International.
ASJC Scopus subject areas
- Condensed Matter Physics
- Mechanics of Materials
- Metals and Alloys