MECHANICALLY ALLOYED FE-ZR-(B,CU) ALLOYS - EFFECT OF COMPOSITION AND HEAT-TREATMENT ON THE MICROSTRUCTURE AND THE MAGNETIC-PROPERTIES

Nanocrystalline Fe86Zr7(B,Cu)(7) alloys were prepared by mechanical al loying of elemental powders, and investigated by X-ray diffraction, di fferential scanning calorimetry and electron microscopy. The as-milled powders consist of supersaturated bcc solid solutions with grain size s of typically 5-10 nm and a small amount of amorphous phase, which de pends on the overall composition of the alloy. The refinement of the c rystal size to the nanometer range is accompanied by an increase in at omic-level strain. Heat treatment at elevated temperatures leads to ch emical redistribution, strain release and grain growth for the bcc sol id solutions prior to the crystallization of the amorphous phase. Both grain growth and strain release depend on the volume fraction of amor phous phase and the particular annealing treatment of the powders. The magnetic properties of the material are discussed with respect to the composition of the material, the deformation and recovery processes d uring milling, and the strain release and the phase transitions upon s ubsequent heating. The results are compared with data for rapidly quen ched materials.