Cryogenic S–N Fatigue and Fatigue Crack Propagation Behaviors of High Manganese Austenitic Steels

Comparative studies on near-threshold fatigue crack propagation behavior of high manganese steels at room and cryogenic temperatures

“…The previous studies on the fractographic observation of FCP-tested high-Mn steels showed that the near-threshold FCP behavior of single phase austenitic steels was greatly influenced by the degree of slip planarity [2,23,24]. High slip planarity would encourage the reversibility of slip at the tip of a crack under fatigue loading, decreasing the FCP rates by reducing the accumulation of fatigue damage [25,26].…”

“…4(c) were obtained from stress-strain curves and may have typical range of error in measurement. These graphs clearly indicate that the nearthreshold FCP behavior of high-Mn steels cannot be understood by tensile properties, unlike the S-N fatigue behavior which shows a strong dependency on tensile strength [2,[21][22][23][24]. No direct correlation was observed between the ΔKth values and yield strength, tensile strength and elastic modulus in the FCP-tested high-Mn steels.…”

“…It has been proposed that the slip planarity of austenitic single phase steels is largely determined by the stacking fault energy (SFE), as well as the grain size [27][28][29]. The slip reversibility for the fatigued specimen with cleavage faceting as dominant fracture mode may roughly be expressed by the ratio between cleavage facet size and grain size [2,[22][23][24]. considerable difference in ΔKth values, the fracture mode of transgranular cleavage faceting was similar for the austenitic steels, including high-Mn and STS304 steels.…”

“…As shown in Table 2, the ΔKth values of 24Mn4Cr and 22Mn3Cr steels at 113 K were similar to those at 173 K. Unlike high-Mn steels, the near-threshold FCP resistance of STS304 steel was further improved at 113 K over the entire ΔK regime. Resultantly, STS304 showed the higher ΔKth value compared to that of high-Mn steels and 9% Ni steel at 113 K. It has been well established that the martensitic transformation during fatigue loading at cryogenic temperatures is responsible for the enhancement in FCP resistance of some austenitic stainless steels, such as STS304 steel [2,30]. The transformation of ε′ martensite from austenite causes volume expansion, inducing compressive stress at the tip of the crack [30].…”

“…Large research efforts have been conducted on developing high manganese (Mn) steels with an excellent strength-ductility combination at ambient and cryogenic temperatures utilizing transformationinduced plasticity (TRIP) and twining-induced plasticity (TWIP) effects [1][2][3]. High-Mn steels with Mn content ranging from 15 to 30 wt.% are to be used in a variety of applications requiring high strength-ductility combination at room and cryogenic temperatures.…”