Observation of FCC-Zr phase in as-cast Zircaloy-4 alloy

[Display omitted] •Face-centered cubic (FCC) phase was firstly reported in as-cast zirconium based alloy.•FCC-Zr phase was successfully indexed both in TEM and TKD.•The formation mechanism of FCC-Zr in as-cast zirconium based alloy was discussed. Face-centered cubic (FCC) phase was firstly reported in cold-rolled Zirconium two years ago, and believed to be introduced by sever plastic deformations. The present study introduces the FCC-Zr phase observed in an as-cast Zirconium alloy. The identification of the FCC-Zr phase was carried out using Transmission Kikuchi Diffraction (TKD) as well as TEM methods. It was found that FCC-Zr in the as-cast Zirconium alloy strictly obeyed the orientation relationship with the HCP-Zr matrix: hcp∥〈1 1 0〉fcc, {0001}hcp∥{11¯1}fcc. In addition, FCC-Zr phases in the as-cast alloy were preferentially precipitated at grain boundaries, due to the intergranular thermal residual stresses among HCP-Zr grains.