| Summary: | In this work, the feasibility of using “grain boundary engineering” to reduce the susceptibility to hydrogen embrittlement in a low carbon low alloy steel was examined. By adding Cu element, the fraction of random grain boundary (RGB) exhibited the highest value in the steel with 1%Cu, while the fraction of special grain boundary (SGB) showed a monotonical decline. The slow strain rate tensile (SSRT) test revealed that the elongation loss presented an increase with Cu addition increasing from 1 % to 3 %. This can be explained in terms of hydrogen diffusion, hydrogen trap and crack propagation. The steel with 1%Cu had a higher fraction of high angle grain boundary (HAGB), which contributed to a higher density of hydrogen traps and a lower hydrogen diffusion rate. Moreover, the steel with 1%Cu had the highest fraction of SGB (∑3, ∑5, ∑7 and ∑≥9), which was beneficial to the resistance to crack propagation. Under the combined effect of RGB and SGB, a higher resistance to hydrogen embrittlement was achieved in the steel with 1%Cu.
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