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 magnetic response. The steel plate of grade IS 2062 having a thickness of 3 mm have been friction stir processed (FSPed) using a tool of tungsten carbide with a 15 mm shoulder diameter along with 3 mm pin diameter with traverse of 150 mm/minute and a 800 RPM revolving speed. Magnetic response of these processed plate and base metal has been recorded using Barkhausen noise (BN) analyzer in terms of BN signal parameters i.e. the rms value and pulse count or number of pulses. Barkhausen noise analysis results have been validated with micro-hardness testing and metallographic study of as received metal and the processed samples. Higher microhardness has been found in processed sample in comparison to the as received metal due to grain refinement owing to the combined effect of plastic flow of material during stirring action of the rotating tool and the frictional heat. Barkhausen noise analysis has been performed in a wide range of magnetic field intensity (MFI) and excitation frequencies to study their effect on variation in rms value and the number of pulses.