Abstract:

Three different Ni-Al foams were synthesized by vapor aluminizing with control of aluminizing time. Oxidation tests under 1100 °C and compression tests were conducted to evaluate the oxidation resistance and compression properties of the foams. X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS) tests were carried out to study the phase composition and microstructure of Ni-Al foams before and after oxidation. Results showed that vapor aluminizing process did not change the foam macro- and microstructure, and the phase composition became from β/γ′-phase to single β-phase as the aluminizing time extending. The Ni-Al foams possessed excellent oxidation resistance, and decreased Al content increased oxidation weight gain and altered oxidation products. Foams containing single β-phase presented obvious brittleness under compression tests, but the foam with β/γ′-phase exhibited elasticity and toughness to a certain extent. The elasticity and toughness of the foams significantly can be improved after oxidation because of the phase changing in matrix during oxidation, and the pre-oxidized high-Al-content Ni-Al foams exhibited good compression properties, as well as excellent oxidation resistance.

Key words: Ni-Al foams, Vapor aluminizing, Oxidation, Compression