A composition includes a metal alloy matrix comprising iron and a plurality of nanoparticles dispersed within the metal alloy matrix. Each nanoparticle of the plurality comprises an oxide of a rare-earth metal and at least one metal selected from the group consisting of tantalum, niobium, vanadium, and titanium. Some compositions include a metal alloy matrix comprising iron and a plurality of nanoparticles comprising at least two different oxides of rare-earth metals dispersed within the metal alloy matrix. Some methods include mixing an oxide of a rare-earth metal with a first metal and a second metal. Other methods include mixing a plurality of particles comprising at least one oxide of a rare-earth metal with a molten metal comprising iron. Each particle of the plurality may exhibit a density between about 6.9 g/cm3 and about 9.0 g/cm3.
