Nondestructive Testing of Dislocations by Magnetic Measurements in the Intermetallic Compounds and the Atomically Ordered Alloys

摘要

The magnetic transition due to plastic deformation was discovered in atomically ordered alloys and intermetallic compounds. The mechanism of magnetic transition due to plastic deformation is explained from the view point of the dislocation theory in the intermetallic compounds. The magnetic transition is caused by the rearrangement of atom pairs in the vicinity of the antiphase boundary between superpartial dislocations. The spontaneous magnetization, M_s, and the induced magnetic anisotropy, K#sigma#, are expressed by a simple function of the dislocation density, #rho#; when superlattice dislocations are distributed making a pair, M_s and K#sigma# change in proportion to #rho#, and when they are distributed independently, M_s and K#sigma# change in proportion to the square root of #rho#. The theoretical results are compared with the experimental and they agree well, if the long range influence is supposed. The relation is applied to the nondestructive tests for the metal fatigue. The values of M_s and K#sigma# give #rho# induced by the external stress ad we can get the exact information of dislocations. The information about the metal fatigue before the cracks appear can be obtained by the magnetic measurements.