Factors influencing fatigue crack propagation behavior of austenitic steels

Critical assessment 19: Stacking fault energies of austenitic steels

“…[1][2][3][4][5][6][7][8][9][10][11] The strengthening mechanism of the fcc steels is strongly dependent upon the stacking fault energy (SFE) of γ austenite. 1,4,8,[10][11][12][13][14][15][16][17][18][19][20][21] It is known that whereas the mechanical stimulation of ε martensite is a dominant strengthening mechanism when the SFE value is less than approximately 20 mJ m −2 , TWIP begins to dominate as the SFE value ranges from 20 to 40 mJ m −2 . 1,2,8,9 For TWIP steels, the SFE influences a 'critical stress' for mechanical twinning, 13,[22][23][24][25][26] the twin fraction [27][28][29] and the twin thickness.…”

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

“…9, including the linear relationship between the ΔKth values and the cleavage facet size/grain size, indicate that slip planarity is an important variable determining the nearthreshold ΔKth value of high-Mn steel. This notion holds as long as the fatigue crack propagates crystallographically within a single grain, as such for austenitic steels in low ΔK regime [2,23,24]. As previously mentioned, the SFE has been proposed as a major factor in determining the sip reversibility during fatigue crack propagation [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.…”

“…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].…”

“…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.…”