Microstructure Characterization and Mechanical Properties of Al Alloyed 9Cr ODS Steels with Different Al Contents

Abstract

The microstructural evolution of different Al contained (0.4, 2.5, and 4.5 wt%) Fe-9wt%Cr ODS steels (hereinafter referred to as 0.4Al-ODS, 2.5Al-ODS, and 4.5Al-ODS) is investigated using XRD and TEM. The XRD analysis shows that the addition of Al into the Fe-9wt%Cr ODS steels leads to the formation of substitutional solid solutions, and the interplanar spacing increases with the increase of Al content. According to TEM bright field image observation, the 0.4Al-ODS steel shows ferrite/martensite duplex microstructure, while 2.5Al-ODS and 4.5Al-ODS steels show a single-phase of ferrite, which is in agreement with the thermodynamic phase diagram calculation. The dispersed particles is mainly Y-Al-O oxide according to EDS analysis, and the Y/Al ratio of most of dispersed particles is less than 1 in all Al alloyed ODS steels. The dislocation density of the three steels is calculated by the residual strain of XRD. The results show that, compared to 2.5Al-ODS and 4.5Al-ODS steels, the 0.4Al-ODS steel contains more dislocations. The strengthening mechanism analysis shows that the modified theoretical hardening models fit well with experimental data of yield strength for 2.5Al-ODS and 4.5Al-ODS steels.

Fabrication of Oxide‐Dispersion‐Strengthened Ferritic Alloys by Mechanical Alloying Using Pre‐Alloyed Powder

“…This usually brings about serious contamination and impairs the efficiency of mass production. [8,9] Thereby, it is a significant issue to reduce the milling time of MA. In the present study, instead of the commonly used Y 2 O 3 (Δ f Hº¼ À1905.31 kJ mol À1 ), the less stabilized TiO 2 (Δ f Hº¼ À944.0 kJ mol À1 ) was selected as one of the starting powders.…”

“…Oxide-dispersion-strengthened (ODS) steel is one of the most promising candidate structural materials for the next-generation fusion reactors due to its excellent resistance to high-temperature creep, corrosion, and neutron radiation. [7][8][9][10][11][12] ODS steels are mainly based on the reduced activated alloys such as Fe-Cr-W system. These alloys can be divided as reduced activated ferritic martensitic (RAFM) steels with a lower Cr (9-12 wt%) content and reduced activated ferritic (RAF) ones with a higher Cr (>12 wt%) content.…”

Strengthening Effect of Multiscale Second Phases in Reduced Activation Ferrite/Martensitic Steel

“…[ 1,2 ] The excellent properties of ODS RAFM steel can be attributed to the fine grain size of the steel and the dispersed nano strengthening phases, such as Y 2 O 3 , MX (M = Ta, V, X = C, N), and M 23 C 6 (M = Fe, Cr). [ 3,4 ] Dispersed Y 2 O 3 particles can not only effectively block dislocation movements but also absorb the vacancies produced by irradiation and the helium generated by transmutation in the nuclear fusion reactor, thereby improving the radiation resistance of the alloy. [ 5 ] Y 2 O 3 particles could be refined by the addition of Ti and Zr to the Fe matrix to form Y–Ti–O and Y–Zr–O clusters.…”

Effect of Thermo-Mechanical Treatment on the Microstructure and Tensile Properties of the Fe-22Cr-5Al-0.1Y Alloy

“…The Ti addition was expected to react with Y and O to form Y-Ti-O oxides within alloys (Y 2 Ti 2 O 7 , Y 2 TiO 5 ) [ 15 ]. The addition of Al in the ODS steel was not only expected to form Y-Al-O oxides [ 16 , 17 , 18 , 19 , 20 ] but also to improve the corrosion resistance by forming dense Al 2 O 3 scales on the surface of the alloy, which limited further corrosion of the matrix under the oxide layer. In addition, the presence of Al can suppress embrittlement at 475 °C by suppressing the phase separation of the ferritic phase into the two phases, Fe-rich ferrite and Cr-rich ferrite in high Cr steel [ 21 , 22 , 23 ].…”