Study on the Effect of Elastic Stress and Microstructure of Low Carbon Steels on Barkhausen Noise

The present study investigates the effect of elastic stress and microstructure on Barkhausen noise in low carbon steels subjected to different heat treatments. Barkhausen noise in an as-received test piece and a test piece heated at 450 ^∘C for 1.5 hours was found to increase with increasing elastic stress. However, in a test piece heated at 700 ^∘C for 10 hours, Barkhausen noise was observed to saturate with increasing elastic stress following an initial increase. To clarify the reason for this saturation behavior, magnetization measurements were carried out and the microstructure and texture of the test pieces were evaluated using microscopy and electron backscatter diffraction. The results indicated that for the test piece heated at 700 ^∘C for 10 hours, a drastic change in the microstructure occurred compared to that for the other test pieces. From the experimental and analytical results, it was concluded that for the former test piece, Barkhausen noise saturated under a low elastic stress due to the globularization of pearlite, which caused 90^∘ domain walls to become 180^∘ domain walls when a low elastic stress is applied.