Fatigue crack growth in two TWIP steels with different stacking fault energies. (May 2017)

• Record Type: Journal Article
• Authors: Yang, H.K.; Doquet, V.; Zhang, Z.F.
• Is Part Of: International journal of fatigue. Volume 98(2017)
• Page Start: 247
• Page End: 258
• Publication Date: 2017-05
• Subjects: TWIP steel -- Fatigue crack growth -- Crack closure -- Mechanical twinning -- Kinematic hardening; Materials -- Fatigue -- Periodicals; Materials -- Fatigue; Periodicals; 620.1122
• DOI: 10.1016/j.ijfatigue.2017.01.034
• Languages: English
• ISSNs: 0142-1123

Abstract

Highlights: Twinning leads to an increasing kinematic cyclic hardening in TWIP steels. Specific constitutive equations capture the change in shape of stress-strain loops. Fe22Mn0.6C steel exhibits more closure effects than Fe22Mn0.6C3Al steel. This is mainly attributed to stronger roughness-induced closure. Fe22Mn0.6C steel however exhibits a lower resistance to fatigue crack growth. Abstract: 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/m 2, 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.