Effects of H segregation on shear-coupled motion of 〈110〉 grain boundaries in α-fe
RIS ID
136278
Abstract
By using large-scale molecular dynamics (MD) simulations, the influence of solute hydrogen (H) segregation into several typical [11¯0] symmetric tilt grain boundaries (STGBs) on the shear response and coupled grain boundary (GB) migration of bicrystals in α-Fe is systematically examined. Depending on our geometric model of coupling for [11¯0] STGBs in body-centred cubic (BCC) metals, two different coupling branches (〈100〉 and 〈111〉) are predicted and further validated by the MD results. Our atomistic simulations show that solute H atoms impede coupled GB motion irrespective of the GB structure, which mainly stems from the fact that H considerably modifies the local atomic structures of the GBs. At high H concentrations, the response of GBs to shear deformation changes from GB coupling to pure GB sliding. In addition, it is found that H can facilitate the vacancy generation via enhancing the interaction of GB dislocations within the framework of the H-enhanced localized plasticity (HELP) mechanism. Although H-vacancy clusters are formed by solute H combining with nucleated vacancies, they cannot grow larger owing to the migration of GBs with extensive dislocation plasticity. This directly prevents the occurrence of H embrittlement (HE). These findings deepen our overall understanding of the role of solute H in GB-mediated plasticity process (GB migration) of metallic materials and provide a possible path to designing new materials with high resistance to HE.
Grant Number
ARC/DP170103092
Publication Details
Li, J., Lu, C., Pei, L., Zhang, C., Wang, R. & Tieu, K. (2019). Effects of H segregation on shear-coupled motion of 〈110〉 grain boundaries in α-fe. International Journal of Hydrogen Energy, 44 (33), 18616-18627.