Influence of the α–α′ phase separation on the tensile properties of Fe-base ODS PM 2000 alloy

The yield and ultimate tensile strengths of an ultrafine grained, oxide dispersion strengthened (ODS) PM 2000 alloy increased during aging at 475 °C. Atom probe tomography and X-ray diffraction analysis revealed that the decrease in lattice parameter and the increases in the yield and ultimate tensile strengths were correlated with phase separation into Fe-rich α and Cr-enriched α′ phases. The lattice misfit between the emerging α and α′ domains and the resulting elastic strain, and the increment of the elastic modulus with aging time due to the corresponding decrease of lattice parameter during α–α′ phase separation, can be regarded as the main causes of hardening.

Research highlights▶ The main cause of hardening is the lattice misfit between α and α′ domains. ▶ Elastic modulus rises since lattice parameter decreases during α–α′ process. ▶ X-ray diffraction analysis revealed the decrease in lattice parameter. ▶ Atom probe tomography reveals a nanometer-scaled α–α′ phase separation. ▶ The modulus effect contributes to 75% of the hardening of PM 2000 alloy.