The effect of Si on hydrogen embrittlement of Fe-18Mn-0.6C-xSi twinning-induced plasticity steels. (15th January 2016)

• Record Type: Journal Article
• Authors: Lee, Sang-Min; Park, Il-Jeong; Jung, Jae-Gil; Lee, Young-Kook
• Is Part Of: Acta materialia. Volume 103(2016)
• Page Start: 264
• Page End: 272
• Publication Date: 2016-01-15
• Subjects: Twinning-induced plasticity steel -- Hydrogen embrittlement -- Brittle-ductile transition -- Deformation twinning -- Austenite-to-martensite phase transformation; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2015.10.015
• Languages: English
• ISSNs: 1359-6454

Abstract

Abstract: The hydrogen embrittlement (HE) of Fe-18Mn-0.6C-xSi (wt.%) twinning-induced plasticity (TWIP) steels was investigated through slow strain rate tensile tests (SSRTs) and thermal desorption analyses of electrochemically H-charged specimens. Whereas the H-charged Si-free steel showed only the (Fe, Mn)O layer with a fcc crystal structure on the surface, the Si-added steels had double oxide layers; the outer layer was a mixture of (Fe, Mn)O and (Fe, Mn)2 SiO4 with an orthorhombic crystal structure and the inner layer was only (Fe, Mn)2 SiO4 . When the Si concentration increased, the (Fe, Mn)2 SiO4 layer became thicker and the charged H concentration decreased. This result indicates that the (Fe, Mn)2 SiO4 layer is effective in suppressing the permeation of H. Both the elongation loss (Eloss ) and the area fraction of the brittle-fractured region increased with increasing Si concentration in the H-charged TWIP steels, particularly in the 3 wt.% Si steel, although the H concentration slightly decreased with increasing Si concentration. The H-charged Si-free and 1.5 wt.% Si steels underwent mechanical twinning and the migration of H atoms from lattices, dislocations and grain boundaries to mechanical twins during the SSRTs. The brittleness of both Si-free and 1.5 wt.% Si steels was caused by H-concentrated mechanical twins. The H-charged 3 wt.% Si steel underwent ε-martensitic transformation as well as mechanical twinning during the SSRT. H atoms migrated to mechanical twins until a strain of 0.24, and then inherited primarily into ε-martensite with further strain. The great Eloss of the H-charged 3 wt.% Si steel was caused mainly by H-concentrated ε-martensite. Graphical abstract: