Magnetism and internal stresses : Concept of magneto-plastic anisotropy

Abstract
This paper deals with the influence of plastic strains and correlated internal stresses on the magnetic properties of a nonoriented 3%Si-Fe alloy. We first studied the mechanical behaviour of the material and evaluated the internal stresses which occur with the strengthening. The alloy exhibits an isotropic mechanical behaviour and three stages of straining. The internal stresses are evidenced thanks to tensile / compressive tests : a high initial increase followed by a gradual one is observed. The internal stresses are linked to the drop of stress at the first stages of the deformation and to the heterogeneous structures of dislocations at higher plastic strain levels. The effect of the internal stresses on the magnetic properties is then discussed. A suitable magnetic frame has been manufactured. Magnetic characteristics are investigated along either the tensile or cross directions. The magnetic properties strongly decrease from the beginning of the plastic strain. Crossing experiments indicate an attenuated effect of the plastic strain on the magnetic properties compared to the colinear measurements. This directionnal effect, called "magnetoplastic anisotropy" seems to be directly linked to the internal stresses.