Piezomagnetic and magnetostrictive properties and structure of Fe-Cu-Nb-Ta-Si-B alloys annealed in vacuum

Magnetic field dependences of magnetomechanical coupling coefficient and moduli of elasticity in Fe73.5Cu1Nb1Ta2Si15.5B7 alloy in as-quenched state and annealed in vacuum for 1 h at temperatures from 300 to 650 degrees C were investigated. The maximum changes of the E (Delta E effect), from 102 to 170 GPa, were observed after annealing at 440 degrees C and from 100 to 165 GPa after annealing at 460 degrees C. The magnetomechanical coupling coefficient after these heat treatments in the temperature range 440-480 degrees C was equal to 0.45-0.47. For the nanocrystalline sample annealed at 560 degrees C, Delta E was equal to zero, i.e., magnetomechanical coupling vanished. The magnetostriction responsible for these phenomena decreased from about 24 x 10(-6) after annealing for 1 h at temperatures of 400-450 degrees C, to 17 x 10(-6), 6 x 10(-6), about 2 x 10(-6) and nearly zero after annealings at 475, 500, 525 and 550 degrees C, respectively. The decrease of the magnetostriction is connected with the formation of the nanocrystalline structure. (C) 1997 Elsevier Science S.A.