Effect of Ni Doping on Strength and Damping Capacity of Fe-Al Alloys

Strength and damping capacity of Fe-Al alloys doped with different amounts of Ni were examined. Fe-Al alloys with an appropriate amount of Ni doping exhibited yield stress higher than 1 GPa and internal friction of above 0.032. In these alloys, the NiAl phase with the B2 structure densely precipitated in the Fe-Al matrix, satisfying the cube-on-cube orientation relationship. The precipitation of NiAl resulted in high strength, which was associated with the difference in primary slip systems between the NiAl precipitates and the Fe-Al matrix. Moreover, the internal friction measured under an external magnetic field showed low values, suggesting that Fe-Al alloys with the NiAl precipitates demonstrated magneto-mechanical damping caused by the irreversible motion of magnetic domain walls. The Al concentration in the Fe-Al matrix became appropriate for damping properties by the precipitation of NiAl, resulting in an increase in the internal friction of the alloy.