Effect of Al addition on low-cycle fatigue properties of hydrogen-charged high-Mn TWIP steels

This study was performed to clarify the effect of Al addition on low-cycle fatigue (LCF) properties of high-Mn twinning induced plasticity (TWIP) steels, which were electrochemically charged by hydrogen. For this purpose, two alloys, Fe-17Mn-0.8C (0Al), and Fe-17Mn-0.8C-2Al (2Al) were used. It was clearly shown that internal hydrogen degraded the resistance to fatigue fracture in both steels. At high strain amplitude, Al addition effectively improved the resistance to hydrogen embrittlement (HE) by preventing intergranular cracking. In contrast, at low strain amplitude, LCF life was reduced more in 2Al than in 0Al, because large-size inclusions in 2Al promoted initiation of fatigue cracks. These results demonstrate that Al addition does not always provide beneficial effect on LCF behavior of TWIP steels in a hydrogen environment, but that the behavior depends strongly on the strain mode or amplitude.