The main damping peaks near 275K, in Mn-20at%Cu alloy, were compared for water-quenched, 10h- and 100h-cooled conditions. Upon assuming a simple relaxation process for the damping behavior, the main damping peaks could be characterized by the peak temperature, the maximum damping capacity and the activation energy. Coherent (101) twin boundaries in the matrix of face-centered tetragonal-structured Mn-rich regions caused a relative tilting of the axes in the 2 twinned fractions. An optimum damping behavior with a lower activation energy was obtained when a suitable Mn concentration was maintained in the Mn-rich regions. Secondary twinning plates were observed in the room temperature microstructure of 100h-treated alloy, and those plates could appreciably decrease the mobility of primary twin boundaries. Discontinuous fringe images were observed; thus indicating the occurrence of structural modulations in the <110> direction.

Tetragonal Distortion-Induced {101} Twinning and Structural Modulation of γMn Phase in a Mn-20%Cu Alloy. F.Yin, Y.Ohsawa, A.Sato, K.Kawahara: Zeitschrift für Metallkunde, 2000, 87[6], .749-54