5 Hydrogen Effects on the Brittleness Transition in BCC Iron Available to Purchase

Recent works on small scales affecting the ductility of single crystal silicon are making an impact on the studies of other brittle materials. At the atomistic and mesoscopic levels, the basic building blocks of plasticity and fracture, as controlled by activation volumes and activation energies, are being used to predict the brittle to ductile transition (DBTT). A unique opportunity produced a first order prediction of how such a transition might be affected by hydrogen in body-centered cubic iron structures. A model derived from observations and analysis of silicon fracture is applied and modified to account for observations of the fracture toughness shift in the transition temperature as affected by hydrogen. For toughness values in the 20 – 60 MPa-m^1/2 range, hydrogen shifts the DBTT by nearly 100K. This is reasonably consistent with a model strongly suggesting it is the average dislocation velocity, as affected by the local stress that controls crack growth kinetics. This affects both crack-tip shielding and bond-breaking which governs the ultimate condition for brittle fracture.