Evolution of nanoheterogeneities and correlative influence on magnetostriction in FeGa-based magnetostrictive alloys

Abstract

Enhanced magnetostriction in FeGa-based alloys has been attributed to the tetragonal modified-D0 3 nanoinclusions. However, the dependence of the magnetostricitive properties on the size and volume fraction of the modified-D0 3 phase remains unclear. Here, the morphology evolution and density change of modified-D0 3 nanoinclusions in (Fe 81 Ga 19 ) 99.9 Tb 0.1 single crystal were characterized by transmission electron microscopy upon in-situ heating process (298 K to 773 K), and their correlative influence on magnetostriction behavior was revealed. The morphology and density of modified-D0 3 nanoinclusions vary slightly when heating temperature is lower than 473 K, leading to the almost unchanged magnetostriction in (Fe 81 Ga 19 ) 99.9 Tb 0.1 alloys. When heating from 473 K to 773 K, modified-D0 3 nanoinclusions evolve into a band-like distribution rather than being randomly distributed in A2 matrix at lower temperature, and the magnetostrictive properties decrease with the increased size of modified-D0 3 nanoinclusions from ~5 nm to ~25 nm during the heating process. The decreased density of modified-D0 3 nanoinclusions caused by phase transition from modified-D0 3 to A2 results in further reduction of magnetostrictive properties when heating at 773 K. The magnetostriction of (Fe 81 Ga 19 ) 99.9 Tb 0.1 single crystal can recover to 325 ppm by quenching from 973 K, which results from the re-precipitation of modified-D0 3 nanoinclusions with small size. The results provide a basis for optimizing the magnetostrictive performance of Fe 81 Ga 19 (Tb) alloys. The enhanced magnetostriction of Fe 81 Ga 19 (Tb) alloys could be obtained by quenching from temperature higher than 773 K. • Evolution of nanoheterogeneities in Fe 81 Ga 19 Tb alloys were investigated by TEM. • The correlation betweenmagnetostriction andevolution of nanoheterogeneities in Fe 81 Ga 19 Tb alloys was established. • It is proposed that quenching from temperature higher than 773 K could optimize the magnetostriction of Fe 81 Ga 19 Tb alloys.