First-principles insights into micro-alloying roles of Zr in Cu–Cr–Zr alloys

Interface has been often neglected in exploring micro-alloying mechanisms in polycrystalline Cu–Cr–Zr alloys. In this study, interface structure modeling and first-principles calculations were carried out to explore the segregation behaviors of micro-alloying element Zr at nano-Cr particle interfaces and a series of low-Σ (Σ ≤ 11) Cu grain boundaries (GBs) in Cu–Cr–Zr alloys. The segregation effects on interface adhesion strength were also evaluated. Our results suggested that Zr can substitute the top-most Cu atoms at most nano-Cr particle interfaces (those with the Nishiyama–Wassermann orientation relation) with the maximal coverage of 1/3 ML. The segregation to other nano-Cr interfaces with the Kurdjumov–Sachs orientation relation is, however, energetically forbidden. At almost all the low-Σ GBs (except the Σ3 (111) only), Zr segregation can be consistently favored up to a full coverage (1 ML), which can improve the GB binding by ∼30%. Based on these results, the multi-fold benefits of Zr micro-alloying were discussed.