Uncovering the Zr segregation behavior and its effect on the fracture strength of Al Σ5 (210) [100] symmetrical tilt grain boundary: Insight from first principles calculation

Abstract

Segregation behavior of Zr solute and its effect on the Al Σ5 (210) [100] symmetrical tilt grain boundary (GB) were investigated through first-principles calculations. Preferential sites and sequence for the replacement of Al by Zr in the GB were determined, so were the fracture energy and tensile strength of the GBs with the varied number of segregated Zr atoms. Segregation energies indicates the GB can accommodate no more than three Zr atoms. The calculation results about grain boundary and strengthening/embrittling energies suggest the strengthening effect of Zr solute on the GB, confirmed by higher fracture energy and peak theoretical tensile stress of the Zr-doped GBs than that of the clean GB, which is the result of the shorter length of the bond that holds the GB together, the contraction of the GB region and the shrink of charge depletion after the segregation of Zr. The conclusions of this investigation shed light on the design of aluminum alloys with high performance GB.