This study investigated the relationship between Mn segregation, damping capacity, and mechanical properties of a Mn–Cu damping alloy after aging at different temperatures. The results showed that after aging, the alloy underwent spinodal decomposition, forming Mn-segregated regions, while α-Mn precipitates appeared at the grain boundaries. The microstructure resulting from spinodal decomposition promoted martensitic transformation, created twin boundaries, and enhanced damping capacity. As the aging temperature increased, the Mn content in the Mn-rich regions gradually rose, thereby raising the martensitic transformation temperature. The twin density first increased and then decreased, which may be attributed to the precipitation and broadening of the α-Mn phase along the grain boundaries of the Mn-rich regions when the aging temperature was too high. At an aging temperature of 425 °C, the tanδ reaches a maximum of 0.05, and the martensitic transformation temperature reaches 100 °C, at which point the tanδ remains 0.04. After aging at 425 °C, a preferred orientation along develops. The [001] orientation has the largest Schmid factor, which is most favorable for the reversible motion of twin boundaries under external stress, thus achieving the highest energy dissipation. To summarize, by promoting the creation of fine {011} twins by means of spinodal decomposition and by increasing the [001] oriented grain fraction through texture development, aging enhances the damping properties of the Mn–Cu alloy. In particular, the aging at 425 °C can provide the best combination of the microstructure and texture conditions, providing the highest damping performance in a wide temperature range.

This study investigated the influence of Mn content (70 wt.%, 75 wt.%, and 80 wt.%) on the microstructure, mechanical properties and damping capacity of Mn-Cu alloys using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), mechanical testing and dynamic mechanical analysis (DMA). The results indicate that during cooling after aging, the Mn-Cu alloy undergoes martensitic transformation, resulting in a dual-phase structure of fcc and fct. The 70 wt.% Mn alloy exhibits a mixed-grain structure with mostly long, straight twin bands, while the 75 wt.% and 80 wt.% Mn alloys consist of fine equiaxed grains with mostly intersecting twin bands. The microstructure determines the properties of the alloy. As the Mn content increases, the mechanical properties initially increase and then decrease, and the 75 wt.% Mn alloy has the best mechanical performance (UTS = 534 MPa, YS = 263 MPa). In contrast, the damping capacity shows a decreasing trend, and the 70 wt.% Mn alloy exhibits the best damping capacity (tanδ = 0.064). The main damping peak of tanδ in Mn-Cu alloys is derived from the relaxation of the twin boundaries, and the less obvious secondary peak is the internal friction peak of martensitic transformation.

The L6 ₀ tetragonal nanoprecipitate phase is crucial for the simultaneous optimization of high magnetostriction and damping in Fe–Ga alloys. However, their widespread industrial application is limited by the high cost of Ga. The fundamental mechanisms governing magnetostriction and damping in the more economical ternary Fe–Ga–Al system, where Al partially substitutes for Ga, remain incompletely understood. This study investigates a -oriented Fe ₈₃ Ga ₁₄ Al ₃ alloy, systematically examining the evolution of its phase structure and functional properties through controlled heat treatments. The directionally solidified state consists of A2, L6 ₀ , and D0 ₁₉ phases, exhibiting a saturation magnetostriction ( λ _s ) of 53 × 10 ⁻⁶ and a total damping capacity of 0.039. Quenching from 730 °C eliminates the D0 ₁₉ phase, resulting in a dual-phase A2 + L6 ₀ microstructure. This treatment increases λ _s to 212 × 10 ⁻⁶ and raises damping to 0.064. Subsequent aging reduces residual stresses, further enhancing total damping to 0.068 while maintaining a high λ _s of 198 × 10 ⁻⁶ . The observed magneto-mechanical hysteresis damping is well described by the Smith–Birchak model. The role of the L6 ₀ phase in the ternary alloy parallels that in its binary counterpart: it induces a tetragonal lattice distortion in the matrix and reduces magnetocrystalline anisotropy, enabling the synergistic enhancement of both magnetostriction and damping. These findings provide a theoretical foundation for designing cost-effective, high-performance Fe–Ga-based functional devices.