Microstructure and tensile properties of Zr-containing ODS-FeCrAl alloy fabricated by laser additive manufacturing

Oxide dispersion strengthened (ODS) FeCrAl alloys have been considered as the promising candidate fuel cladding materials for the Gen-IV fission reactors due to excellent radiation tolerance, mechanical properties and corrosion resistance , but their manufacturing is complex process. Laser engineered net shaped (LENS) technology followed by post-build heat treatment was employed successfully to fabricate Zr-containing ODS-FeCrAl alloy. The microstructure of as-deposited and heat-treated alloys was characterized by optical microscope (OM), electron backscatter diffraction (EBSD), scanning electron microscope (SEM) and high-resolution transmission electron microscope (HRTEM). The tensile tests were carried out at room temperature. The results show that the coarse columnar grains with preferred orientation ([001] fibre texture) are obtained after LENS deposit and are remained after post-build heat treatment. The average width of columnar grains for both as-deposited and heat-treated samples is ~180–190 μm. A slag-like layer which is made up of Y 3 Al 5 O 12 , ZrO 2 and Al 2 O 3 is observed at the surface of deposited sample. Some coarse appendage oxides which consist of Al 2 O 3 and Y 4 Zr 3 O 12 are distributed in the matrix of as-deposited sample. Post-build heat treatment produces high-density nanoscale Y 4 Zr 3 O 12 oxides in the matrix. The formation mechanism of different type oxides is explained. Both as-deposited and heat-treated samples present anisotropic tensile properties . After post-build heat treatment, the tensile strength is improved significantly by the formation of high-density nanoscale Y 4 Zr 3 O 12 .