Magnetism and internal stresses: Concept of magneto-plastic anisotropy

This paper deals with the influence of plastic strains and correlated inter nal stresses on the magnetic properties of a nonoriented 3%Si-Fe alloy. Pie first studied the mechanical behaviour of the material and evaluated the i nternal 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 initia l 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 leve ls. The effect of the internal stresses on the magnetic properties is then discussed. A suitable magnetic frame has been manufactured. Magnetic charac teristics are investigated along either the tensile or cross directions. Th e magnetic properties strongly decrease from the beginning of the plastic s train. Crossing experiments indicate an attenuated effect of the plastic st rain on the magnetic properties compared to the colinear measurements. This directionnal effect, called "magnetoplastic anisotropy" seems to be direct ly linked to the internal stresses.