Softening of the Al-Mg-Si-Fe alloy under magnetostriction of FeAl microinclusions

The physical origin of the magnetoplastic effect was experimentally identified in Al polycrystalline alloy. Exposure of the nominally pure industrial Al-Mg-Si-Fe alloy to magnetic field 0.7 T induces residual changes that provide a creep rate increase up to 25% and microhardness decrease down to 30%. FeAl inclusions of ∼1 μm size were revealed in the alloy. Magnetostriction of the ferromagnetic inclusions providing local mechanical stresses and generation of fresh dislocations in the vicinity of the inclusions is the main reason for magnetoplasticity. Ferro-, antiferro-, and paramagnetic contributions of the inclusions and/or Fe atoms distributed in the Al matrix have been distinguished. The chemical composition of FeAl inclusions determined by transition electron microscopy and local field probed by the Mossbauer technique are in good agreement with saturation magnetization of the FeAl alloys.