Abstract
Stainless steels with harmonic-structure design have a great balance of high strength and high ductility. Therefore, it is imperative to investigate their fatigue properties for engineering applications. In the present work, the harmonic-structured SUS316L stainless steels were fabricated by mechanical milling (MM) and subsequent hot isostatic pressing (HIP) process. A series of ratcheting-fatigue tests were performed on the harmonic-structured SUS316L steels under stress-control mode at room temperature. Effects of grain structure and stress-loading conditions on ratcheting behavior and fatigue life were investigated. Results showed that grain size and applied mean stress had a significant influence on ratcheting-strain accumulation and fatigue life. Owing to the ultrafine grained structure, tensile strength of the harmonic-structured SUS316L steels could be enhanced, which restrained the ratcheting-strain accumulation, resulting in a prolonged fatigue life. A higher mean stress caused a faster ratcheting-strain accumulation, which led to the deterioration of fatigue life. Moreover, a modified model based on Smith–Watson–Topper (SWT) criterion predicted the ratcheting-fatigue life of the harmonic-structured SUS316L steels well. Most of the fatigue-life points were located in the 5 times error band.
Highlights
Austenitic stainless steels have excellent mechanical properties and corrosion resistance, and are often used as structural materials in petrochemical equipment, nuclear equipment, and medical equipment [1,2,3]
It is noted that the grain structure a great influence on ratcheting both ratcheting and fatigue life
Materials.the the ratchetratcheting-strain rates deformation, and steels were nearly stable in the ing-strain ratesofofthe theharmonic-structured harmonic-structured steels were nearly stable in secondary the sec- stage, which may indicate that the structure in the structure was stable under ondary stage, which may indicate thatdislocation the dislocation structure in harmonic the harmonic structure stress cycling was stable under stress cycling
Summary
Austenitic stainless steels have excellent mechanical properties and corrosion resistance, and are often used as structural materials in petrochemical equipment, nuclear equipment, and medical equipment [1,2,3]. It is imperative to realize high strength and high ductility in stainless steels for structural safety. These types of equipment are often subjected to cyclic loading in service. Structural materials with heterogenous microstructures have been proposed to achieve excellent mechanical properties and good fatigue resistance [7,8,9,10,11,12,13,14,15].
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