Effect of Microstructural Characteristics on Mechanical Properties of Austenitic, Ferritic, and γ-α Duplex Stainless Steels

Mitsuhiro Okayasu, Daiki Ishida

Research output: Contribution to journalArticle

Abstract

Materials properties of γ (austenite), α (ferrite), and γ-α duplex stainless steels were experimentally examined using samples with different grain sizes (8 to 1000 µm) and different ratios of the γ to α phase (γ proportion: 35 to 78 pct). The mechanical properties (hardness and tensile strength) of the duplex stainless steel were about 1.5 times higher than those of the austenitic and ferritic stainless steels. Two main reasons for the high strength of duplex stainless steel were identified as follows: (i) severe interruption of slip deformation in the γ phase on the α phase; (ii) a high misorientation angle around phase boundaries between the γ and α phases, caused by bonding of the different lattice structures: γ-fcc and α-bcc. The ultimate tensile strength of duplex stainless steel increased with increasing proportion of the γ phase to 50 pct, but decreased with a further increase in the amount of γ phase. The mechanical properties improved with decreasing grain size of the stainless steels, which follows the Hall–Petch relationship; however, the reverse relationship was obtained for ferritic stainless steel, especially with large grain sizes (100 to 1000 µm), in which the size of hard Cr23C6 precipitates increased with increasing grain size.

Original languageEnglish
JournalMetallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
DOIs
Publication statusAccepted/In press - Jan 1 2019

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Stainless Steel
stainless steels
Stainless steel
mechanical properties
Mechanical properties
grain size
ferritic stainless steels
tensile strength
proportion
Ferritic steel
Tensile strength
austenitic stainless steels
interruption
austenite
high strength
misalignment
ferrites
precipitates
slip
hardness

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Mechanics of Materials
  • Metals and Alloys

Cite this

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title = "Effect of Microstructural Characteristics on Mechanical Properties of Austenitic, Ferritic, and γ-α Duplex Stainless Steels",
abstract = "Materials properties of γ (austenite), α (ferrite), and γ-α duplex stainless steels were experimentally examined using samples with different grain sizes (8 to 1000 µm) and different ratios of the γ to α phase (γ proportion: 35 to 78 pct). The mechanical properties (hardness and tensile strength) of the duplex stainless steel were about 1.5 times higher than those of the austenitic and ferritic stainless steels. Two main reasons for the high strength of duplex stainless steel were identified as follows: (i) severe interruption of slip deformation in the γ phase on the α phase; (ii) a high misorientation angle around phase boundaries between the γ and α phases, caused by bonding of the different lattice structures: γ-fcc and α-bcc. The ultimate tensile strength of duplex stainless steel increased with increasing proportion of the γ phase to 50 pct, but decreased with a further increase in the amount of γ phase. The mechanical properties improved with decreasing grain size of the stainless steels, which follows the Hall–Petch relationship; however, the reverse relationship was obtained for ferritic stainless steel, especially with large grain sizes (100 to 1000 µm), in which the size of hard Cr23C6 precipitates increased with increasing grain size.",
author = "Mitsuhiro Okayasu and Daiki Ishida",
year = "2019",
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doi = "10.1007/s11661-018-5083-4",
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journal = "Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science",
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AB - Materials properties of γ (austenite), α (ferrite), and γ-α duplex stainless steels were experimentally examined using samples with different grain sizes (8 to 1000 µm) and different ratios of the γ to α phase (γ proportion: 35 to 78 pct). The mechanical properties (hardness and tensile strength) of the duplex stainless steel were about 1.5 times higher than those of the austenitic and ferritic stainless steels. Two main reasons for the high strength of duplex stainless steel were identified as follows: (i) severe interruption of slip deformation in the γ phase on the α phase; (ii) a high misorientation angle around phase boundaries between the γ and α phases, caused by bonding of the different lattice structures: γ-fcc and α-bcc. The ultimate tensile strength of duplex stainless steel increased with increasing proportion of the γ phase to 50 pct, but decreased with a further increase in the amount of γ phase. The mechanical properties improved with decreasing grain size of the stainless steels, which follows the Hall–Petch relationship; however, the reverse relationship was obtained for ferritic stainless steel, especially with large grain sizes (100 to 1000 µm), in which the size of hard Cr23C6 precipitates increased with increasing grain size.

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