EFFECT OF DEFORMATION TEMPERATURE ON THE MICROSTRUCTURE OF HARD MAGNETIC FeCr22Co15 ALLOY SUBJECTED TO TENSION COMBINED WITH TORSION DEFORMATION MODES

The paper presents the results of microstructure evolution studies of hard magnetic FeCr22Co15 alloy deformed until destruction by tension and torsion in the temperature range 725-850 degrees C. The temperatures and deformation rates resulted from the condition of superplasticity occurrence in the Fe-Cr-Co alloys. Observations of the longitudinal sections of the deformed samples in the scanning electron microscope showed the formation of a weak gradient microstructure with the highest grain refinement in the surface layer of the material. Increasing the deformation temperature from 725 to 850 degrees C increased the homogeneity of the deformation along the tensile axis of the sample. It also brought about the increase of grain size and slight increase of the thickness of fine grains in the surface layer. The precipitation of the intermetallic sigma-phase was also observed with its maximum amount in the zones of the highest deformation.