61 research outputs found
Exchange Effects in the Invar Hardening: as a test case
An increase of the critical resolved shear stress of Invar alloys (Invar
hardening) with a lowering temperature is explained. The effect is caused by a
growth of the exchange interaction between dangling -electron states of
dislocation cores and paramagnetic obstacles (e.g., Ni atoms in FeNi alloys)
which occurs below the Curie temperature. The spins of the two electrons align
along the magnetization due to the exchange interaction with the surrounding
atoms of the ferromagnetic. The exchange interaction between the dislocations
and obstacles is enhanced in Invars due to a strong growth of the magnetic
moments of atoms under the action of elastic strains near the dislocation
cores. Parameters characterizing the exchange interaction are determined for
the case of the FeNi Invar. The influence of the internal
magnetic field on the dislocation detachment from the obstacles is taken into
account. The obtained temperature dependence of the critical resolved shear
stress in the FeNi Invar agrees well with the available
experimental data. Experiments facilitating a further check of the theoretical
model are suggested.Comment: 8 pages, 2 figure
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