Influence of Magnetic Pretreatment on the Thermoplastic Effect in Aluminum Alloys Containing Ferromagnetic Inclusions

We report our findings on how a magnetic pretreatment influences the thermoplastic effect in aluminum alloys containing ferromagnetic inclusions. The alloys were exposed to a static magnetic field and then tested in creep under uniaxial tension. The morphology of the alloys was studied by scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction. Their specific heat and the work done in plastic deformation were calculated using thermomechanical data. The results demonstrate that there is a relation between magnetostriction, mechanical stress on the matrix–inclusion interface, and energy dissipation during deformation. Magnetic pretreatment of the material has been shown to increase its specific heat by five times (from 0.05 to 0.26 J/m3) and the work done in its deformation by 44% (from 0.72 to 1.04 J/m3). The observed increase in Taylor coefficient (from 0.07 to 0.25) and latent energy (from 0.67 to 0.78 J/m3) is due to the stress redistribution on the matrix–inclusion interface as a consequence of magnetostriction. The estimated magnetostriction-induced mechanical stress exceeds the creep limit of the matrix, which accounts for the increase in energy dissipation. The results of this study can be useful in designing “smart” materials with programmable properties that can be controlled by varying the composition, particle size, and percentage of a magnetically active filler in a nonmagnetic matrix.