THE DEVELOPMENT OF THE PHASE COMPOSITION IN MELT-SPUN GD4FE77.5B18.5 ALLOYS WITH THERMAL TREATMENT - A COMBINED NMR AND MOSSBAUER STUDY

摘要

The types of atomic short-range orders (SROs) in the amorphous alloy Gd4Fe77.5B18.5 and its crystallization products under different thermal-treatment conditions were investigated by means of spin-echo nuclear magnetic resonance (NMR) and Mossbauer spectroscopy. it was found that there exist two kinds of SROs in the amorphous alloy: body-centred tetragonal (BCT) Fe3B- and orthorhombic (o) Fe3B-like SROs. The crystallization products differ at various annealing temperatures: the sample annealed at 670 degrees C for 10 min consists of BCT Fe3B containing Gd and alpha-Fe, without the Gd2Fe14B phase; the sample annealed at 860 degrees C for 60 min contains BCT Fe3B, Gd1.1Fe4B4 and alpha-Fe; and the sample crystallized at 1010 degrees C for 10 min consists of Fe2B, alpha-Fe, Gd2Fe14B and Gd1.1Fe4B4. The experimental results indicate that the B-11 NMR peak shifts from 34.7 MHz for pure BCT Fe3B in the sample annealed at 860 degrees C for 60 min to 36.0 MHz for the sample annealed at 670 degrees C for 10 min and the relative intensity of the third Mossbauer sub-spectrum, corresponding to the Fe-III(8g) site of BCT Fe3B, is about 6% less than those of the other two. These facts can be explained in terms of the entering of Gd atoms into the BCT Fe3B phase. [References: 24]