[SY-K5] Symposium K-5

[SY-K5] Combined analysis of first-principles calculations and fracture mechanics experiments on intergranular embrittlement of an alloy steel

^○Masatake Yamaguchi (Center for Computational Science and e-Systems, Japan Atomic Energy Agency, Japan)

A significant loss of fracture toughness (K_Ic) is induced by intergranular (grain boundary; GB) segregation of metalloid solute (Sb, Sn, and P) in a Ni-Cr steel. However, the atomistic mechanism has not been clarified from a multiscale point of view. From first-principles calculations, it is shown that segregated solute with higher energetic stability on fracture surfaces causes a larger linear reduction in the ideal work to intergranular fracture (2γ_int ); i.e. the energy difference between a GB and its two fracture surfaces. The combined analysis with first-principles calculations and fracture mechanics experiments found several orders of magnitude more energy loss in K_Ic for a specific range in the 2γ_int within only a few tenths of J/m². These results illustrate that the GB of steel has the threshold energy of atomic cohesion under which catastrophic failure occurs [1]. [1] M. Yamaguchi and J. Kameda: Phil. Mag. 94, 2131-2149 (2014).