Achieving well-balanced mechanical properties and oxidation resistance of an oxide dispersion strengthened nickel-based alloy via in-situ solid-state reaction

Abstract

An oxide dispersion strengthened nickel-based alloy with balanced mechanical strength, ductility and oxidation resistance was prepared. Ni20Cr3Al and nano Ti powders were mechanically milled in an atmosphere of Ar+20%Air. Ti powder was partly oxidized to be TiO2 during the milling and spark plasma sintering. The others are dissolved into the nickel-based alloy and form coherent intermetallic phase of Ni3Ti. Owing to the higher affinity of Al than Ti to O, most TiO2 particles were transformed to be in-situ nano Al2O3 dispersoids with good coherency to the alloy matrix as well. Grain refinement and precipitates strengthening contribute largely to the greatly improvement of mechanical strength of the NiCrAl–2Ti alloy, of which the yield strength reaches 884 MPa and ductility is 10.72%. Besides, the refined grains promote the selective oxidation of Al, ensuring an extremely high oxidation resistance. Its oxidation rate constant (kp) is as low as 9.7 × 10−8 mg2 cm−4 s−1 at 900 °C.