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

• DOI: 10.1016/j.jmrt.2022.03.188
• Publication Date: 2022-04-06T23:39:23Z
• Authors: Yingbo Zhang; Dening Zou; Xiaoqiao Wang; Yunong Li; Miaomiao Li; Fan Wang; Wei Zhang; Libo Tong
• Keywords: Diffusionless transformation

Aimed at clarifying δ→γ transformation and M23C6 precipitation behavior in18Cr-xAl-Si (x = 0, 0.43wt.%, 0.91wt.% 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 δ-ferrite, same time free energy difference between δ-ferrite γ-austenite, which increased difficulty transformation, in turn transformation. γ-austenite preferentially precipitated phase boundaries gradually along sides as decreased, part martensite transformed inside phases. carbides mainly γ-austenite/martensite. With increase content, amount γ-austenite/martensite decreased. In addition, solidification mechanism complex nucleus also discussed.