Microstructural evolution of ultrafine-grained NiCrCoAl foil after heat treatment at 1000°C

This research investigated the microstructural evolution of Ni-23·5Cr-2·66Co-1·44Al superalloy foil fabricated by electron-beam physical vapour deposition and annealed at 1000°C. The results showed that the deposited alloy mainly consisted of the γ-phase. After annealing at 1000°C, the peak moved to a lower 2è degree on the deposited side and to a higher 2è degree on the substrate side, which indicated that uniform strain existed at the deposited state and recovery occurred during annealing. With an increase in the annealing time, the (220) diffraction peak increased significantly. The average size of the grains increased and showed zigzag structures after being etched by a mixture of HNO₃, HCl and HF etchant. After being annealed at 1000°C for 4 hours, the ultimate tensile strength of the Ni-23·5Cr-2·66Co-1·44Al superalloy foil was improved from 641 to 800 MPa.