Damping capacity, magnetic and mechanical properties of Fe-18Cr alloy

Iron-chromium based alloys are known as potentially high damping corrosion-resistance alloys with good mechanical properties and workability. The main structural mechanism of enhanced damping in the Fe-Cr alloys is magneto-mechanical coupling due to reversible and irreversible motion of magnetic domain walls, which is also linked with magnetostriction of the alloys. In order to create new complex alloyed materials with improved functional properties, it is important to study experimentally the basic relation between structure, mechanical and functional properties of binary Fe-Cr alloys. In this paper, we used cold-rolled sheets of a high-purity Fe-18Cr alloy to study the correlation between heat treatment, grain size, damping capacity and magnetostriction. Damping capacity of the samples was measured at bending using forced vibrations by means of dynamical mechanical analyzer Q800 TA Instruments and using free-decay of bending vibrations in different structural states after various annealing treatments. The results show that the optimal properties for Fe-18Cr binary alloy were achieved after annealing of cold-rolled sheets at 840 degrees C. Homogenizing by annealing at 1200 degrees C for 3 h before the final heat treatment shifts the annealing temperature for maximal damping capacity to 900 degrees C with approximately the same value of damping capacity and decreases mechanical properties due to the significant increase in the grain size. Slow cooling of the samples after high-temperature annealing causes a marked decrease of the impact toughness, reduction of damping capacity and an increase in the coercive force of the Fe-18Cr alloy. This effect can be explained by spinodal decomposition of the a-solid solution and formation of local zones enriched with Cr or Fe.