ODS alloy with ferritic-austenitic duplex matrix and NiAl precipitation prepared by master alloy approach

Abstract

A ferritic-austenitic duplex matrix alloy strengthened by NiAl and nanosized oxides was developed by the combination of computational-aided alloy design and the master alloy approach. The master alloy route promotes the solid solution and the diffusion-homogenization of Mo in the matrix. The small lattice misfit (0.42%) between α-Fe matrix and β' precipitates stabilizes the coherent interface by lowering the elastic strain energy, favouring near-spherical particle morphology and reducing the driving force for competitive coarsening. The duplex matrix microstructure contains mainly submicron-sized (0.2–0.8 μm) ferritic grains with a large volume fraction of β' precipitates and a small amount of coarse grained austenite. A high population of oxide dispersion with particle size of 10–30 nm distributed uniformly in the matrix. The alloy exhibits enhanced strength and improved ductility both at room temperature and elevated temperature. The compressive strength of the heat treated sample is as high as 2053 MPa, 964 MPa and 672 MPa at room temperature, 650 °C and 700 °C, respectively. The compressive ductility (strain to failure) of the alloy is about 12% at room temperature.