Role of deformation twins in magnetic heterogeneity of MC 1100 and Barkhausen noise emission

This paper deals with the surface heterogeneity in the near-surface region of the high strength low alloyed steel MC 1100. The remarkable surface thermal softening takes place due to decarburization during hot rolling, which in turn avoids very fine short twins within the grain interior during the accelerated cooling. The depth and extent of this twin-free region strongly vary along the sheet width, whereas this effect only fringes along the sheet length. The high sensitivity of the Barkhausen noise technique against the variable depth extent of short twins free region originates from the interaction among the domain walls in motion and lattice imperfection in which very fine short twins play a strong role due to their high pinning strength. The study demonstrates that the influence of residual stresses can be neglected. On the other hand, evolution between the tensile stress and Barkhausen noise is strongly altered as a function of microstructure heterogeneity. For this reason, employing the Barkhausen noise technique to monitor the stress state of components made of MC 1100 in real operation can be a quite complex task.