Evaluation of Fatigue Properties under Four-point Bending and Fatigue Crack Propagation in Austenitic Stainless Steel with a Bimodal Harmonic Structure

Austenitic stainless steel (JIS-SUS304L) with a bimodal harmonic structure, which is defined as a coarse-grained structure surrounded by a network of fine grains, was fabricated using powder metallurgy to improve both the strength and ductility. Four-point bending fatigue tests and K-decreasing test...

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Published inFrattura ed integritá strutturale Vol. 13; no. 48; pp. 545 - 553
Main Authors Kikuchi, Shoichi, Nakatsuka, Yuta, Nakai, Yoshikazu, Nakatani, Masashi, Kawabata, Mie, Ameyama, Kei
Format Journal Article
LanguageEnglish
Italian
Published Cassino Gruppo Italiano Frattura 01.04.2019
Subjects
Air temperature
Austenitic stainless steels
Bend strength
Bending fatigue
Crack closure
Crack propagation
Ductility
Ductility tests
Fatigue
Fatigue failure
Fatigue limit
Fatigue tests
Fracture mechanics
Grain refinement
Growth rate
Mechanical milling
Metal fatigue
Metallurgy
Pore formation
Powder
Powder metallurgy
Stainless steel
Steel structures
Stress intensity
Stress propagation
Stress ratio
Threshold stress
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Summary:Austenitic stainless steel (JIS-SUS304L) with a bimodal harmonic structure, which is defined as a coarse-grained structure surrounded by a network of fine grains, was fabricated using powder metallurgy to improve both the strength and ductility. Four-point bending fatigue tests and K-decreasing tests were conducted in air at room temperature under a stress ratio R of 0.1 to investigate fatigue crack propagation in SUS304L. The fatigue limit of this harmonic-structured material was higher than that of the material with a homogeneous coarse-grained structure. This is attributable to the formation of fine grains by mechanical milling and to the suppression of pore formation. In contrast, the threshold stress intensity range, DKth, for the harmonic-structured material was lower than that for the homogeneous coarse-grained material, while the crack growth rates, da/dN, were higher at comparable DK. These results can be attributed to a reduction in the effective threshold stress intensity range, DKeff,th, due to the presence of fine grains in the harmonic structure.
ISSN:1971-8993
1971-8993
DOI:10.3221/IGF-ESIS.48.52