Phase transformations and microstructure evolutions during depressurization of hydrogenated Fe–Mn–Si–Cr alloy. (29th March 2023)

• Record Type: Journal Article
• Authors: Varanasi, Rama Srinivas; Koyama, Motomichi; Saitoh, Hiroyuki; Utsumi, Reina; Sato, Toyoto; Orimo, Shin-ichi; Akiyama, Eiji
• Is Part Of: International journal of hydrogen energy. Volume 48:Number 27(2023)
• Page Start: 10081
• Page End: 10088
• Publication Date: 2023-03-29
• Subjects: High pressure -- Phase transformation -- Epsilon martensite -- Hydride -- Synchrotron radiation X-ray diffraction; Hydrogen as fuel -- Periodicals; Hydrogène (Combustible) -- Périodiques; Hydrogen as fuel; Periodicals; 665.81
• DOI: 10.1016/j.ijhydene.2022.11.274
• Languages: English
• ISSNs: 0360-3199

Abstract

Abstract: Hydride formation and associated phase transformations have been extensively studied in pure Fe. However, the understanding of hydrogenation in Fe-based alloy systems is still lacking. Such an investigation is particularly important in the case of austenitic (face-centered cubic) steels given that hydrogen has been reported to alter the austenite phase stability. In the current work, we investigate the phase transformations associated with depressurization of non-hydrogenated and hydrogenated Fe–Mn–Si–Cr alloy (FMS) (Fe-28.84Mn-7.04Cr-6.14Si, in mass %) using in-situ x-ray diffraction technique. Additionally, we study the change in microstructure using electron backscatter diffraction (EBSD) and electron channeling contrast imagining (ECCI). Highlights: We report phase transformations during depressurization of non-hydrogenated (FMS) and hydrogenated (FMS H ) Fe–Mn–Si–Cr alloy. Constituent phase of FMS at 9 GPa, 973 K is HCP. Cooling and depressurization resulted in the formation of FCC + HCP phases. Cooling and depressurization of FMS H (from 9 GPa, 973 K) caused the transformation from DHCP + HCP → DCHP + HCP + FCC. Extensive microscopic and nanoscopic cracking have been observed in the depressurized FMS H . 3 microstructural morphologies in the depressurized FMS H : (1) Ultra-fine globular (2) Coarse lamellar (3) 'Fingerprint' like.