Structure of melt-spun Fe-Ga-based magnetostrictive alloys

Fe1-xGax (x = 0.17, 0.21, 0.25 and 0.3) alloys were rapidly quenched by the melt-spinning technique to determine the maximumGa concentration that retains the disordered bcc (alpha-Fe) phase at room temperature. The texture of the ribbons as a function of melt-spinning parameters and annealing was also extensively studied. All of the as-spun samples were found to be crystalline. For x = 0.17, only the disordered bcc phase was found and for x = 0.25 and 0.3, primarily DO3 phase was found, while for x = 0.21, the phase is bcc at high wheel speed and DO3 at low speed. For the free side of the as-spun ribbons, the easy growth axis (100) of alpha-Fe or of DO3 tilts about 10degrees to 20degrees from the ribbon normal and (011) is along the ribbon length. This texture does not change significantly with wheel speed. The texture on the wheel side of the ribbon is close to random at high speed but increases with slower speed. For Fe83Ga17, 900 degreesC annealing reduces the tilt angle while 1100 degreesC annealing recrystallizes the grains and produces strong (100) out of plane texture but randomizes the directionality in the plane. Annealing with sulfur addition was found to enhance the [100] texture but did not produce the desired (100) along the longitudinal direction of the ribbon. The saturation magnetostriction, lambda(s) of as-spun Fe79Ga21 and Fe83Ga17 both having a disordered bcc structure and strong (100)(011) texture was measured as 98 and 130 ppm, respectively, along the ribbon length.