Towards theoretical connection between tensile strength of a grain boundary and segregated impurity concentration: Helium in iron as an example

A theoretical method is proposed to investigate the tensile strength dependence on the impurity concentration in metals using a first-principles method in combination with the classical thermodynamics models. In the present study, helium (He) in an iron (Fe) grain boundary (GB) is taken as an example. The theoretical tensile strength of an FeΣ5(310)/[001] GB with different amounts of He impurity is determined using first-principles computational tensile tests (FPCTT) and the He concentration is derived depending on the solution energy and temperature using thermodynamics models. Thus, the dependence of the tensile strength of an Fe GB on He concentration is established, and a critical He concentration is defined using the amount of the tensile strength reduction compared with that of a clean GB. Such a method is expected to be quite useful in predicting the impurity-induced degradation of the mechanical properties of metals.