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Effect of Al content on the δ→γ transformation and M23C6 precipitation behavior in 18Cr-xAl-Si ferritic heat-resistant stainless steel during solidification process

Aimed at clarifying δ→γ transformation and M23C6 precipitation behavior in18Cr-xAl-Si (x = 0, 0.43wt.%, 0.91wt.% and 1.82wt.%) ferritic heat-resistant stainless steel (FHSS), high temperature confocal scanning laser microscopy (CSLM) was used for in-situ observation during solidification. The result...

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Bibliographic Details
Published in:Journal of materials research and technology 2022-05, Vol.18, p.3104-3114
Main Authors: Zhang, Yingbo, Zou, Dening, Wang, Xiaoqiao, Li, Yunong, Li, Miaomiao, Wang, Fan, Zhang, Wei, Tong, Libo
Format: Article
Language:English
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Summary:Aimed at clarifying δ→γ transformation and M23C6 precipitation behavior in18Cr-xAl-Si (x = 0, 0.43wt.%, 0.91wt.% and 1.82wt.%) ferritic heat-resistant stainless steel (FHSS), high temperature confocal scanning laser microscopy (CSLM) was used for in-situ observation during solidification. The results demonstrated that increasing of Al content reduced the nucleation temperature of δ-ferrite, and at the same time reduced the free energy difference between δ-ferrite and γ-austenite, which increased the difficulty of δ→γ transformation, in turn reduced the temperature of δ→γ transformation. The γ-austenite preferentially precipitated at the δ-ferrite phase boundaries and gradually along the sides of the δ-ferrite phase boundaries as the temperature decreased, and part of the martensite transformed inside the γ-austenite phases. M23C6 carbides mainly precipitated at the phase boundaries between δ-ferrite and γ-austenite/martensite. With the increase of Al content, the amount of γ-austenite/martensite and M23C6 carbides decreased. In addition, the solidification mechanism of the complex nucleus was also discussed.
ISSN:2238-7854
DOI:10.1016/j.jmrt.2022.03.188