The Influence of Alloying Segregation on Zinc-Induced Embrittlement at the α/γ-Fe Interface

Zinc-assisted liquid metal embrittlement (LME) crack propagation is often intergranular and occurs following the interphase (alpha/gamma) boundaries. In this work, the influence of alloying element X (Al, Cr, Mn, Mo, Nb and Ti) in steel segregation on zinc-induced embrittlement at the alpha/gamma-Fe interface was investigated using first principles methods. The calculations predict that Nb and Mn (Mo, Al and Ti) atoms from the gamma bulk allow energetically favorable segregation to the gamma(alpha) side of the interfacial site, while the Cr atom tends to partition to the alpha-Fe matrix. Compared to Al, Ti, Mn and Cr, Zn has a stronger tendency to enrich at the alpha/gamma interphase boundaries and matrix. Our results demonstrate that the presence of Zn atoms weakens the bonding of iron atoms at the interface, while the segregation of Al, Mn, Mo, Nb and Ti atoms increases Zn-induced interface cohesion. It was also found that the segregation of X atoms changes the charge environment around the alpha/gamma-Fe interface and affects the bond characteristics among metal atoms, which reduces the detrimental effect of Zn. Based on the effect of segregation on the interfacial cohesion, Al, Mn, Mo and Ti atoms, which show a preferable tendency to segregate to the alpha/gamma interface, are considered beneficial elements to improve the thermodynamic stability at the zinc-induced alpha/gamma-Fe interface.