Abstract
This study investigates the hydrogen embrittlement (HE) behavior of Nickel-201 alloy using the oligocrystal approach. To comprehend the influence of microstructure toward HE, various types of tensile oligocrystals (True-oligocrystals, Quasi-oligocrystals, Identical-oligocrystals, and Bi-crystal type oligocrystals) with diverse microstructure (in terms of Schmid factor distribution and grain boundary types) are generated using a combination of heat treatment and slicing method. The electron backscatter diffraction (EBSD) analysis is used to validate the development of the desired tensile oligocrystal samples. Identical oligocrystal samples established the transition in fracture mode from ductile transgranular (TG) to brittle intergranular (IG), solely driven by hydrogen uptake. Post-tensile deformation analysis validated the hydrogen-induced IG fracture initiation and propagation along the random high-angle grain boundaries (RHAGBs) only. Bi-crystal type oligocrystals with low angle grain boundaries (LAGBs) and coincident-site lattice (CSL) Σ3 grain boundaries exhibited resistance to hydrogen-induced intergranular fracture, thus establishing the ‘special’ nature of these grain boundaries against the HE under current testing conditions.
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