Magnetic behaviour of low-carbon steel in parallel and perpendicular directions to tensile deformation

Degradation of a low-carbon steel with plastic tension has been investigated after unloading by magnetic methods (hysteresis and Barkhausen noise (BN) emission). The measurements were done with magnetization in parallel as well as in perpendicular direction to the previous elongation. The dislocation structure formation was checked by transmission electron microscopy (TEM). Evolution of magnetic parameters with applied strain was examined and applicability of magnetic methods for non-destructive testing (NDT) is discussed. It was concluded that the change of the two-peak profile of BN envelope and differential permeability (leading to hysteresis loop bulging) in the parallel direction to the one-peak profile in the perpendicular direction is due to the deformation-driven accumulation of residual stresses.