Mossbauer effect and its applications in materials research

It is generally recognized that in any well behaved metal fatigue failure, the following sequence of events occurs. The application of stress causes the movement of defects already present in the specimen, besides producing new defects. These defects concentrate in the regions of stress concentration. This defect concentration, which precedes crack nucleation and its eventual growth, actually amounts to environmental changes for Mossbauer atoms located in these regions. Changes in the atomic composition of the Mossbauer absorber atom environment are sensed by examining changes in the sensitive parameters of the Mossbauer spectra. A preliminary study of changes in the isomer shift and line width of commercial nonmagnetic steel specimen is reported.