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AM: Magnetismus

AM 8: Dauermagnetische Werkstoffe und Legierungen

AM 8.6: Talk

Tuesday, March 27, 2001, 12:45–13:00, S 5.4

Effect of Preparation on Amorphization and Magnetic Properties in Nd-Fe-Co-Al-B Alloys — •G. Kumar, J. Eckert, S. Roth, W. Loser, and L. Schultz — Institute of Metallic Materials, IFW Dresden, 01069 Dresden.

We studied the effect of alternative preparation methods (copper mold casting, melt spinning, and mechanical attrition) on properties of Nd₅₇Fe₂₀Co₅Al₁₀B₈ and Nd₄₀Fe₄₀Co₅Al₈B₇ alloys. All differently prepared samples exhibit different thermal, and magnetic properties, irrespective of similar diffraction patterns. The cast Nd₅₇Fe₂₀Co₅Al₁₀B₈ rod exhibits crystallization at 790 K followed by melting at 810 K. Mechanically alloyed powders and ball-milled prealloys reveal two exothermic DSC peaks in the range of 650-850 K. The J-H hysteresis loops of samples synthesized by different routes show that the unique atomic order responsible for hard magnetic properties can only be accessed at moderate cooling rate of the melt as realized in copper mold casting. Rapidly quenched ribbons, mechanically alloyed powders, and ball-milled ingots do not show hard magnetic properties at room temperature. These results indicate that amorphous samples with different local atomic order can be prepared by different processing routes.