Effect of impurity and alloying elements on Zr grain boundary strength from first-principles computations

Effects of twenty impurity and alloy elements on the strength of a Zr(0 0 0 1)/Zr(0 0 0 1) ∑7 twist grain boundary were studied using a first-principles density functional approach. A ranking in the order of most weakening to most strengthening was: Cs, I, He, Te, Sb, Li, O, Sn, Cd, H, Si, C, N, B, U, Ni, Hf, Nb, Cr, and Fe. Segregation energies for these elements to the grain boundary and the Zr(0 0 0 1) surface were also calculated. Calculations showed that the weakening grain boundary elements He, I, and Cs have a strong driving force for segregation to the grain boundary from bulk Zr. Zircaloy cladding failures (pellet-clad interactions) in commercial fuel systems and separate effects test results provide context for these computational results.