The damping Behavior of Ni added Mn-Cu damping alloys

The temperature and frequency dependent damping behavior of Ni added Mn-Cu alloys were investigated. Ni addition not only increased the magnitude of the phase-transformation damping peak, but also decreased its frequency dependence. A decreased transformation temperature was found in the Ni added Mn-Cu alloys under the same treating condition, which suggested a retarding effect of Ni on the decomposition of gamma(Mn) phase during the slow-cooling process. The characteristic twin-boundary damping peak of Mn-Cu alloys was enlarged and broadened with the addition of Ni. According to the relaxation damping models the twin-boundaries in Ni added alloys had the larger activation energy, and also exhibited a broader distribution of relaxation time during the stress induced movement. In Ni added Mn-Cu alloys, the FCT gamma(Mn) phase showed a larger axis ratio. c/a and the Cu-rich gamma(Mn) phase coexisting with the FCT phase showed the similar lattice constants at ambient temperature. These microstructural features in Ni added Mn-Cu alloys might contribute to the improved damping behavior of the twin-boundary damping peak.