Effect of zinc-doping on tensile strength of Σ5 bcc Fe symmetric tilt grain boundary

Abstract

Liquid-zinc-induced embrittlement in the Σ5 [1 0 0] 36.8° symmetric tilt grain boundary (STGB) of bcc Fe is investigated using the first-principles computational tensile test (FPCTT). The result reveals that the strength and ductility of the grain boundary (GB) decrease after zinc doping. In addition, the effect of zinc on the chemical bond and electronic structure of the GB is investigated, and the result shows that Zn segregation either breaks or weakens the surrounding interface of the Fe (2)–Fe (−2) bond, reducing the bond strength. The reasons for the this reduction include both physical and electrochemical factors: The physical factor involves the expansion of the bcc Fe GB, the increase of the Fe (2)–Fe (−2) bond length, and the weakening of the Fe (2)–Fe (−2) bond strength by Zn, while the electrochemical factor involves the formation of a covalent bond between the Zn (1) and Fe (2) atoms, which reduces the charge density between the Fe (2) and Fe (−2) atoms and weakens the Fe (2)–Fe (−2) bond strength.