Abstract
The magnetostriction constants, λ100 and λ111, of Sendust alloys (7∼11 wt%Si, 4∼7 wt%Al, bal. Fe) were determined as a function of temperature between -196°C and 120°C by means of the strain gauge method. For the central composition of Sendust alloy (9.6 wt%Si, 5.7 wt%Al, bal. Fe), the sign of λ100 is positive at -196°C and the magnitude of λ100 is fairly large (≅1.3 × 10-5). With increasing temperature, the magnitude of λ100 gradually becomes small and crosses zero at room temperature. With continued increasing temperature, λ100 again increases (-2 × 10-6 at 120°C). In λ111, however, no sign change took place for most of the alloys examined in this temperature range and the magnitude of λ111 is nearly constant (e.g.,-1 × 10-6 for the central composition of Sendust alloy). The composition at which λs=(2/5) λ100+(3/5)/λ111 becomes zero is strongly temperature dependent. With increasing temperature, the compositional line of λs=0 moves to the area with rich Fe and less Si concentration in the Fe-Si-AI ternary alloy system. The compositions at which λs=0 and K1=0 are both realized exist on the composition line of about 84 wt%Fe. These composition shift to lower Si concentration along this composition line with increasing temperature.
