In order to suppress the formation of large Y-Al-O particles in the Al-containing oxide dispersion strengthened (ODS) steels, spherical Zr/Hf hydride nanoparticles (NPs) of 21 +/- 6 nm and 16 +/- 4 nm were prepared by the hydrogen plasma metal reaction (HPMR) method and added as raw particles to produce the ODS Fe-14Cr-3Al-2 W-0.35Y(2)O(3 )steels using mechanical alloying (MA) and hot isostatic pressing (HIP). Zr/Hf hydride NPs gave rise to the formation of fine complex oxide NPs, Y(4)Zr(3)O(12 )of 14.2 +/- 8.1 nm and Y(2)Hf(2)O(7 )of 9.1 +/- 6.9 nm. These oxide NPs were semi-coherent with the matrix, (4 (32) over bar)(Y4Zr3O12)//D = 2.57 x 10(-17)m(2)/s)(alpha-Fe). and (D = 1.54 x 10(-17)m(2)/s)(Y4Zr3O12)//D = 6.25 x 10(-12)m(2)/s)(alpha-Fe) With the increasing atomic number of IVB group element (from Ti to Hf), the addition of its hydride NPs can create finer complex oxide nanoparticles in the Alcontaining ODS steels and bring about higher mechanical properties. The tensile strength of the 14Cr-3Al ODS steel added with 0.1 wt% Hf hydride NPs exhibited a tensile strength of 1067 MPa at 25 degrees C and 284 MPa at 700 degrees C, higher than those ODS steels added with 0.1 wt% Zr/Ti hydride NPs. Furthermore, the ODS steel added with Hf hydride showed a large uniform elongation of 11.5% at 25 degrees C. The addition of Hf hydride NPs is promising to develop high performance Al-containing ODS steels. (C) 2018 Elsevier B.V. All rights reserved.