Barkhausen noise analysis of friction stir processed steel plate

This work investigates the variation in material properties of steel upon friction stir processing through its magneticresponse. The steel plate of grade IS 2062 having a thickness of 3 mm have been friction stir processed (FSPed) using a toolof tungsten carbide with a 15 mm shoulder diameter along with 3 mm pin diameter with traverse of 150 mm/minute and a800 RPM revolving speed. Magnetic response of these processed plate and base metal has been recorded using Barkhausennoise (BN) analyzer in terms of BN signal parameters i.e. the rms value and pulse count or number of pulses. Barkhausennoise analysis results have been validated with micro-hardness testing and metallographic study of as received metal and theprocessed samples. Higher microhardness has been found in processed sample in comparison to the as received metal due tograin refinement owing to the combined effect of plastic flow of material during stirring action of the rotating tool and thefrictional heat. Barkhausen noise analysis has been performed in a wide range of magnetic field intensity (MFI) andexcitation frequencies to study their effect on variation in rms value and the number of pulses.