Effects of alloying elements on cohesion and brittleness of grain boundary of iron

First-principles calculation is performed to systematically investigate the effects of alloying elements (Cr, Mo, Ni, Pb, and Bi) on stability, cohesion strength, Young's modulus, and fracture toughness of the n-ary sumation 3(111)[110] grain boundary (GB) of BCC Fe. It is found that compared with Cr, Mo, and Ni, both Pb and Bi are energetically more favorable to segregate to GB and decrease the GB energy of Fe. Calculations also reveal that Pb and Bi have an important effect to significantly reduce the cohesion strength, Young's modulus, and fracture toughness of GB of Fe, and that such an effect of Bi seems bigger than that of Pb. The derived results are discussed in terms of electronic structure and are in good agreement with experimental and theoretical results in the literature, which could provide a deep understanding of the intrinsic mechanism of the effects of Pb and Bi on embrittlement of BCC Fe.

Automated summary

First-principles calculation was used to investigate the effects of alloying elements on the properties of BCC Fe grain boundaries. It was found that Pb and Bi are more favorable for segregation to the grain boundary, but significantly reduce its properties.