Magnetic Barkhausen noise for the study of magnetic anisotropy in stainless steels

ABSTRACT The magnetic Barkhausen noise (MBN) is a phenomenon that occurs in ferromagnetic materials when they are exposed to slowly varying magnetic fields, generating discrete jumps in their magnetization. These jumps are produced by the movement of the magnetic domain walls. They can be detected by a small coil allocated on the sample surface. The movement of the domain wall is regulated by the microstructure of the material (precipitates, grain size, residual stresses, etc.). Through this indirect way it is possible to characterize the material. In this work MBN measurements to study magnetic anisotropy induced by rolling processes and uniaxial strain tests are shown for ferritic stainless steels AISI: 409, 430 and 441A. The measurements were made at different strain percentages. The objective was to follow the changes in the MBN signals. The metallographic and hardness studies are presented. The results show a clear trend related with the direction of the principal stresses.