On the stress vs. Barkhausen noise relation in a duplex stainless steel

Various parameters of a Barkhausen noise burst were measured under applied stress in prestrained duplex stainless steel specimens. After quenching, the root mean square value of the Barkhausen noise amplitude was low because of the compressive macroscopic and interphase macrostresses in the ferrite phase. Prestraining increased the amplitude of the Barkhausen noise in all measuring directions due to reduction of macroscopic compressive residual stress and introduction of tensile interphase microstresses in the ferrite phase. Under applied stress, Barkhausen noise measured in the loading direction behaved similarly to ferritic steels: Barkhausen noise increased under tensile stress and decreased under compressive stress. In the direction transverse to the loading axis, the Barkhausen noise response was anomalous: Barkhausen noise increased or remained unchanged under macroscopic compressive strain in the transverse direction and decreased under tensile strain in the transverse direction. In unstrained specimens in the loading direction, applied stress vs. Barkhausen noise showed a linear relation under the applied stress range from −200 to 250 MPa. The stress sensitivity of the Barkhausen noise was, however, low. In the prestrained specimens, the stress sensitivity was higher than in the unstrained specimens, especially under applied compressive stress.