Novel cast-aged MnCuNiFeZnAl alloy with good damping capacity and high usage temperature toward engineering application

Novel cast-aged Mn-26.0Cu-2.0Ni-2.0Fe-2.0Zn-3.0Al (wt.%) alloy with good damping capacity and high usage temperature has been well designed and developed in this work, which can act as a promising candidate toward engineering applications. The microstructure, damping capacity and usage temperature were investigated systematically by X-ray diffraction, optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, and dynamic mechanical analyzer. The results show that heat treatment has a significant influence on the damping capacity and usage temperature of as-cast MnCuNiFeZnAl alloy. Compared to the original as-cast alloy with internal friction (Q^-1) of 3.0 × 10^-2 at a strain amplitude ε = 2 × 10^-4 and usage temperature of 43 °C, the largest Q^-1 (5.0 × 10^-2) and highest usage temperature (70 °C) can be obtained simultaneously by ageing treatment at 435 °C for 2 h, while homogenization-ageing, solution-ageing and overageing can just result in the limited improvement of damping capacity and usage temperature. This is because the highest nanoscale Mn segregation in Mn dendrites can be formed by spinodal decomposition during ageing, while carrying out the homogenization or solution treatment prior to the ageing, as well as overageing treatment can cause the weakening of Mn segregation at the macro/nano-scale and even the precipitation of α-Mn, thus leading to the undesirable damping capacity and usage temperature.