Examination of Barkhausen noise parameters for characterisation of strain-induced martensitic transformation in AISI 304 stainless steel

In this study, the strain-induced martensitic transformation in AISI 304 stainless steel after tensile deformation was investigated using different magnetic Barkhausen noise (MBN) parameters. For this purpose, different amounts of martensite phase were formed in AISI 304 stainless steel by different amounts of tensile deformation. The amount of strain-induced martensite phase in the steel samples was quantified by XRD patterns. The MBN profile and the RMS voltage of the MBN parameters were employed in order to evaluate the microstructural changes. The MBN parameters (RMS and peak height) increased with the amount of deformation and this was attributed to the volume fraction of magnetic domains and pinning sites increasing with the increase in martensite content. It was suggested that the growth of martensite laths provided wider areas for the motion of domain walls and their interaction with obstacles within the martensite, resulting in an increasing rate of change in the RMS values and the width of the MBN profile with martensite content. However, the coalescence of martensite packets decreased the number of Barkhausen signals being emitted from the austenite-martensite interface areas, resulting in a decrease in the slope of the peak height curve with increasing martensite content.