INTERNAL-FRICTION IN A MAGNETICALLY TREATED MATERIAL WITH DISLOCATIONS

Internal friction of magnetically treated tin-bronze has been investig ated as a function of the degree of dislocation pinning caused by an i mpurity-defect atmosphere. It is found that pulsed magnetic field trea tment of this material can affect its internal friction in different w ays, After pulsed magnetic field treatment the level of internal frict ion can be higher than in the untreated material if, as a result of ag ing processes preceding this treatment, a dislocation impurity-defect atmosphere is formed, and can be lower if a qualitatively new impurity -defect atmosphere is formed on the dislocations as a result of earlie r treatment, or it can remain unchanged in the absence of atmospheres at the dislocations. The observed character of of internal friction in pulsed magnetic field treated material is linked with the presence of localized magnetically active centers excited by such treatment, whic h can lead to a change in the interaction energy of the atmosphere wit h a dislocation. (C) 1997 American Institute of Physics.