Dresden 2017 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 3: Topical Session: Interface-Controlled Microstructures: Mechanical Properties and Mechano-Chemical Coupling - Segregation and Embrittlement I

MM 3.4: Talk

Monday, March 20, 2017, 11:15–11:30, BAR 205

Effects of alloying elements on H embrittlement of C segregated grain boundaries in bcc Fe — •Aparna P. A. Subramanyam, Abril Azocar Guzman, Xiang Huang, Rebecca Janisch, and Alexander Hartmaier — ICAMS, Ruhr University-Bochum, Bochum, Germany

The cohesion of grain boundaries (GBs) is dependent on their chemical composition and structure and greatly influences the mechanical properties of the material. It is well known that H prefers segregating to the GBs (and other defects). H enhanced decohesion is one important mechanism of H embrittlement. Therefore it is necessary to understand the effects of alloying additions on the segregation behaviour of H and on the embrittling mechanism.

The embrittling effects of H in the presence of alloying elements Mn, Cr, V and C at the Σ5(310)[001]36.9^∘ STGB and for selected cases, Σ3(112)[110] STGB in α-Fe was investigated by performing spin polarized DFT calculations with respect to a varying number of alloying elements and H atoms at different segregation sites of the GBs. The impact of co-segregation of Mn-C-H, Cr-C-H, V-C-H on GB energy, work of separation and theoretical strength has been studied. Uni-axial tensile tests were performed perpendicular to the GB and theoretical strength was determined from energy-displacement data fitted using the universal binding energy relationship. The thermodynamic model of Rice and Wang was used to determine the (cohesion enhancing or weakening) nature of the segregated elements. Based on our results, we discuss the alloying strategy to prevent H embrittlement of GBs.