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Open AccessArticle

Tensile Properties and Microstructural Evolution of an Al-Bearing Ferritic Stainless Steel at Elevated Temperatures

by Ying Han 1,*, Jiaqi Sun 1, Yu Sun 2, Jiapeng Sun 3 and Xu Ran 1,*
1
Key Laboratory of Advanced Structural Materials, Ministry of Education, Changchun University of Technology, Changchun 130012, China
2
National Key Laboratory for Precision Hot Processing of Metals, Harbin Institute of Technology, Harbin 150001, China
3
College of Mechanics and Materials, Hohai University, Nanjing 211100, China
*
Authors to whom correspondence should be addressed.
Metals 2020, 10(1), 86; https://doi.org/10.3390/met10010086
Received: 29 November 2019 / Revised: 24 December 2019 / Accepted: 27 December 2019 / Published: 4 January 2020
(This article belongs to the Special Issue Thermomechanical Processing of Steels)
The influence of temperature and strain rate on the hot tensile properties of 0Cr18AlSi ferritic stainless steel, a potential structural material in the ultra-supercritical generation industry, was investigated at temperatures ranging from 873 to 1123 K and strain rates of 1.7 × 10−4–1.7 × 10−2 s−1. The microstructural evolution linked to the hot deformation mechanism was characterized by electron backscatter diffraction (EBSD). At the same strain rate, the yield strength and ultimate tensile strength decrease rapidly from 873 K to 1023 K and then gradually to 1123 K. Meanwhile, both yield strength and ultimate tensile strength increase with the increase in strain rate. At high temperatures and low strain rates, the prolonged necking deformation can be observed, which determines the ductility of the steel to some extent. The maximum elongation is obtained at 1023 K for the strain rates of 1.7 × 10−3 and 1.7 × 10−2 s−1, while this temperature is postponed to 1073 K once decreasing the strain rate to 1.7 × 10−4 s−1. Dynamic recovery (DRV) and continuous dynamic recrystallization (CDRX) are found to be the main softening mechanisms during the hot tensile deformation. With the increase of temperature and the decrease of strain rate (i.e., 1123 K and 1.7 × 10−4 s−1), the sub-grain coalescence becomes the main mode of CDRX that evolved from the sub-grain rotation. The gradual decrease in strength above 1023 K is related to the limited increase of dynamic recrystallization and the sufficient DRV. The area around the new small recrystallized grains on the coarse grain boundaries provides the nucleation site for cavity, which generally results in a reduction in ductility. Constitutive analysis shows that the stress exponent and the deformation activation energy are 5.9 and 355 kJ·mol−1 respectively, indicating that the dominant deformation mechanism is the dislocations motion controlled by climb. This work makes a deeply understanding of the hot deformation behavior and its mechanism of the Al-bearing ferritic stainless steel and thus provides a basal design consideration for its extensive application. View Full-Text
Keywords: ferritic heat resistant stainless steel; hot tensile deformation; tensile property; dynamic recrystallization; flow behavior ferritic heat resistant stainless steel; hot tensile deformation; tensile property; dynamic recrystallization; flow behavior
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Han, Y.; Sun, J.; Sun, Y.; Sun, J.; Ran, X. Tensile Properties and Microstructural Evolution of an Al-Bearing Ferritic Stainless Steel at Elevated Temperatures. Metals 2020, 10, 86.

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