Evaluation of EB-PVD deposited Ni–Cr–Al alloy foil

Abstract

Ni–Cr–Al alloy foils were deposited at 900 °C from a target of Ni–Cr–Al alloy by EB-PVD, and then annealed at 760 °C in a high vacuum furnace for 16 h. Microstructure of as-deposited foil consisted of a large amount of fine grains with mean size of 90 nm. However, after annealing the grains grew obviously to an average size of 4 μm. In addition, long range chemical ordering of L1₂ type emerged in the annealed specimens, while no evidence of ordering structure were found in the deposited samples. The as-deposited foil exhibited a strong {111} texture on the evaporation side. Twin substructure was dominated within grains of as-deposited and annealed samples. The mechanical properties of the foils were examined using room tensile tests. The ultimate tensile strength of as-deposited and annealed samples is 780 and 767 MPa, respectively. Investigation of fracture surfaces from samples revealed that brittle fracture took place along boundaries of columnar crystals formed on the substrate side, while the equiaxed dimples were dominant on the evaporation side.