2003 Volume 44 Issue 9 Pages 1671-1674
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 γMn 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 γMn phase showed a larger axis ratio, c⁄a and the Cu-rich γMn 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.