Tetsu-to-Hagane
Online ISSN : 1883-2954
Print ISSN : 0021-1575
ISSN-L : 0021-1575
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Improvement of Powdering Resistance of Zn-Fe Galvannealed Coating by Controlling of Its Composition and Microstructure: Verification with Sputtering Method
Aimi UchiyamaKohei KawasakiYuji Sutou Daisuke AndoJunichi Koike
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2019 Volume 105 Issue 7 Pages 724-732

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Abstract

Improvement of the powdering resistance of galvannealed (GA) coatings is a key issue in automotive GA steel sheets. To make the relationship between powdering resistance and microstructure of GA layer, sputtering fabrication process was used to prepare Zn-Fe intermetallic films with various composition and microstructure in this study. Zn-Fe films with 1500 nm in thickness were deposited on an iron substrate by RF magnetron sputtering. Г+Г1 two-phase film (17.2~24.4 at.%Fe) was found to show a severe powdering by 3-point bending test, while Г1 (16.2 at.%Fe) or Г (34.3 at.%Fe) single-phase films showed much better powdering resistance. These results indicate that Г/Г1 interfaces boundaries have a low interfacial strength compared to that of Г/iron or Г1/iron interfaces. To improve the low powdering resistance of the Г+Г1 two-phase film, we investigated the effect of grain size refinement by B addition on the powdering resistance. It was found that the grain size refinement by B addition drastically improves the powdering resistance of Г+Г1 two-phase film. The decrease in the fracture toughness of Г+Г1 two-phase film by grain refinement was suggested to cause the improvement of its powdering resistance.

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© 2019 The Iron and Steel Institute of Japan

This article is licensed under a Creative Commons [Attribution-NonCommercial-NoDerivatives 4.0 International] license.
https://creativecommons.org/licenses/by-nc-nd/4.0/
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