Fatigue crack growth in two TWIP steels with different stacking fault energies

Yang H.K. (1) , Véronique Doquet (2) , Zhang Z.F. (1)

1 Shenyang National Laboratory for Materials Science
2 LMS - Laboratoire de mécanique des solides

Fatigue crack growth tests with R=0 and 0.4 were carried out on Fe-22Mn-0.6C and Fe-22Mn-0.6C-3Al (wt. %) Twinning-Induced Plasticity (TWIP) steels with stacking fault energies around 21.5 and 37 mJ/m2, respectively. The former exhibits more crack closure effects, partly due to stronger asperity-induced closure. Strain-controlled push-pull tests followed by scanning electron microscope observations show that both steels are prone to mechanical twinning under low-cycle fatigue, associated with an increasing kinematic hardening. Twinning is however more profuse in Fe-22Mn-0.6C steel. Elastic-plastic finite elements simulations of crack growth, using specific constitutive equations able to capture the increasing kinematic hardening suggest that plasticity-induced crack closure is lower in Fe-22Mn-0.6C steel. Even after closure corrections, the Al-free steel, exhibits a lower resistance to fatigue crack growth, which is attributed to a pronounced strain localisation at the crack tip, and maybe also to environment effects.

Mots clés: TWIP steel; Fatigue crack growth; Crack closure; Mechanical twinning; kinematic hardening

Domaines: Mécanique des matériaux [physics.class-ph]

Yang H.K., Véronique Doquet, Zhang Z.F.. Fatigue crack growth in two TWIP steels with different stacking fault energies. International Journal of Fatigue, 2017, ⟨10.1016/j.ijfatigue.2017.01.034⟩. ⟨hal-01449918⟩