Crystalline Transformations in Amorphous Fe73.5Cu1Nb3Si16.5B6 Alloy

The crystallization behavior of the amorphous Fe73.5Cu1Nb3Si16.5B6 alloy has been investigated by Mössbauer spectroscopy and X-ray diffractometry. Fine crystalline grains of about 10 nm diameter are produced uniformly by annealing at 550°C for 1 hour in nitrogen atmosphere. The predominant crystalline phase is assigned to the Fe-Si alloy with DO3 structure and neither intermetallic compounds nor an amorphous phase can be recognized in the Mössbauer spectrum. The addition of 1 at% Cu to amorphous Fe-Si-B merely brings about a lowering of the crystallization temperature, while that of 3 at% Nb leads to a rise in the crystallization temperature and simultaneous formation of Fe-Si alloy and Fe3(Si, B). Their effects simultaneously influence the crystallization behavior in the amorphous Fe73.5Cu1Nb3Si16.5B6 alloy, and lead to the production of Fe-Si alloy with uniform ultrafine grains. Annealing at 720°C for 1 hour gives rise to the growth of the fine grains and the formation of Fe3(Si, B).