Phase transformation of stainless steel during fatigue

Cyclic Deformation Behaviour of Three Austenitic Cast CrMnNi TRIP/TWIP Steels with Various Ni Content

“…The steel 16Cr‐6Mn‐3Ni with the highest tendency for a martensitic transformation shows the highest fatigue life times in the HCF regime. This crossover of the fatigue life curves depending on the austenite stability was found also by Franke et al 6 and Hennessy et al 18 and was explained by beneficial effects of an ongoing martensitic transformation at low strain amplitudes. A local martensitic transformation in advantageously oriented grains hinders dislocation movements and reduces thus the plastic deformation 6, 7.…”

“…Thus, it is concluded that the martensitic phase transformation in these alloys occurs via the ε‐martensite, i.e. γ → ε → α' as already observed in other metastable austenitic steels 5, 18. The low SFE in these steel variants favours initially the transformation into a hexagonal structure instead of mechanical twinning as observed in the variant 16Cr‐7Mn‐8Ni.…”

Connection between deformation-induced dislocation substructures and martensite formation in stainless steel

“…The saturation stress amplitude is mainly determined by the bowing stress of screw dislocation in the interior of dislocation cells. Generally, cyclic plasticity-induced martensite transformations considerably decreases fatigue lifetime under strain-controlled conditions, whereas the opposite is true for constant stress amplitude experiments, according to Hennessy et al [31]. Laird et al [32] and Winter et al [33] observed that high strain amplitudes induce multiple slip systems to facilitate the formation of dislocation cell substructures in LCF deformation.…”

Sensitivity of the magnetization curves of different austenitic stainless tube and pipe steels to mechanical fatigue

“…Some of these magnetic methods are based on measuring strain-induced martensite fractions formed in meta-stable austenitic stainless steels (ASS) since fatigue of ASS is accompanied by a transformation of the paramagnetic face centred cubic phase (cfcc) into body centred tetragonal martensitic phase (a 0 -bct) which is ferromagnetic [1][2][3]. The corresponding changes of magnetic properties can be detected by measuring the eddy current impedance, the magnetic permeability and the remanence field.…”