Role of Si concentration on the magnetic and mechanical behavior of rapidly solidified Fe-Si laminations

The magnetic and mechanical properties of rapidly solidified Fe-Si laminations have been investigated as a function of Si concentration in the range 3 wt% - 7.8 wt%. Magnetic loss (d.c. - 10 kHz) and tensile stress-strain experiments, carried out as a function of grain size, put in evidence the magnetic softening and the mechanical hardening following the increase of the Si concentration. In particular, when the concentration cSi = 6.7 wt% is attained, the total loss passes, at all frequencies, through a minimum value, which correlates with the vanishing of the magnetostriction constant. At the same time, mechanical hardening occurs, with monotonical increase of yield stress and work hardening rale with cSi. The magnetic analysis, while showing, on the one hand, a direct link between coercivity and magnetostriction, puts in evidence the relationship existing between the hysteresis and the excess loss components and leads to a quantitative assessment of the overall energy loss dependence on the Si content. A Hall-Petch law for the yield stress and the fracture stress vs. grain size is verified at all compositions. This permits one, in particular, to single out a direct contribution to material hardening coming from phase ordering when cSi >∼ 4 wt %.