A first principles investigation of zinc induced embrittlement at grain boundaries in bcc iron

Using density-functional theory calculations we study the embrittling behaviour of liquid Zn in the Σ 3 [ 1 1 1 ] 60 ° and the Σ 5 [ 1 0 0 ] 36.8 ° symmetric tilt grain boundaries in bcc iron (ferrite). Investigating Zn induced changes in energetics of the grain boundaries and their associated free surfaces we utilise both a canonical and a grand-canonical thermodynamic model to discuss the embrittling behaviour of liquid zinc. Our results show that Zn wetting significantly destabilises the grain boundaries, but the conclusion which GB is more susceptible to embrittlement depends on the mechanism, as well as on the concentration.