Abstract
The magnetic properties of steels are affected by plastic deformation, because the domain wall processes magnetoelastically interact with the dislocations and the residual stresses. The evolution of the magnetic hysteresis loop and its parameters with the type and degree of straining can thus provide a macroscopic signature of the underlying the mechanical and structural properties. Additional information can be achieved at a microscopic level through analysis of the Barkhausen noise, the signal generated by the stochastic flux variations associated with the discontinuous motion of the domain walls. Nondestructive methods for the structural evaluation of magnetic steels, devoted, in particular, to the investigation of work-hardening and state of internal stress following plastic straining, have therefore been developed in the literature, either through magnetic hysteresis or Barkhausen noise measurements. In this paper, we summarize significant results regarding the relationship between magnetic properties and plastic deformation in steel samples and the related experimental methods. Attention will be devoted, in particular, to the measurement and analysis of the Barkhausen noise spectral density and the way it relates to the macroscopic magnetic behavior and the structural properties.
Highlights
Iron and iron-based alloys spontaneously expand when ferromagnetism sets in below the Curie temperature
The energy of interaction between uniaxial stress σ and magnetization M forming an angle θ is obtained, per unit volume, as Eσ = (3/2)λs σsin2 θ. It is precisely this energy term that enters the magnetic phenomenology of the plastically deformed steels. Investigating such a phenomenology has obvious direct interest for steel sheets applied as magnetic cores of electrical devices, like transformers and motors, but it has great appeal for the nondestructive assessment of the mechanical properties of the structural steels
The previously discussed dependence of the macroscopic magnetic properties on type and magnitude of plastic deformation has an obvious counterpart in the evolution of the magnetization process at a microscopic/mesoscopic level,ofwhere pinning and magnetic unpinning properties of the domain walls (DWs)
Summary
Iron and iron-based alloys spontaneously expand when ferromagnetism sets in below the Curie temperature. The energy of interaction between uniaxial stress σ and magnetization M forming an angle θ is obtained, per unit volume, as Eσ = (3/2)λs σsin θ It is precisely this energy term that enters the magnetic phenomenology of the plastically deformed steels. Investigating such a phenomenology has obvious direct interest for steel sheets applied as magnetic cores of electrical devices, like transformers and motors, but it has great appeal for the nondestructive assessment of the mechanical properties of the structural steels. We shall consider both the macroscopic material response, in terms of hysteresis loop and coercivity, and the microscopic aspects of the magnetization reversal, through analysis of the Barkhausen noise This work contains both unpublished results by the authors and results from the literature. The latter are duly mentioned and tuned to this presentation by fully original figures
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