The Mechanism of Damping in Manganese-Copper Alloys

AbstractBy obtaining a clearer understanding of the mechanism of damping operating in manganese-copper alloys it may be possible either to improve damping properties at elevated temperatures or to select alternative systems with better ancillary properties. Electron-microscope, X-ray, and neutron-diffraction techniques have been used to identify those microstructural features thought to be responsible for the high damping capacity of manganese-copper. Only those compositions that are tetragonal have a high damping capacity. The tetragonality is induced by an antiferromagnetic ordering of manganese ions and the Neel temperature is associated with the drastic fall in damping capacity as the temperature is raised. The structural distortion caused by the cubic → tetragonal transformation creates microtwins and it is the nucleation and growth of these twins that is thought to give rise to the vibrational energy absorption.