Flow stress behavior of polycrystalline Ni under combined magneto- and acousto-plastic effects

The effects of an alternating magnetic field (50 Hz, 6.4 × 104 A/m) and an ultrasonic deformation (2 × 104 Hz, 5 × 10−5) on the flow stress of polycrystalline nickel during unidirectional tension at 290 K have been investigated in detail. Special attention is paid to clarify the mechanism of the magneto-plastic (MPE) and acousto-plastic (APE) joint effects. The combined MPE + APE effect is found to be smaller than the sum of the individual ones. An experimental procedure allowed synchronization and consecutive shifts in phase between beginning of the application of the magnetic field period and the initiation of the ultrasonic deformation. The combined MPE + APE is found to be dependent on the phase shift with extremes at 170° and 350°. Considering both magnetically and thermally activated dislocation motion, a differential equation is proposed describing the deformation process in magnetically and ultrasonically induced stress fields. Calculated dependencies of stress on time and strain correlate well with experimental results and clarify the revealed extremes.