Rapid solidification; amorphous; nanocrystalline; glass forming ability; Finemet; soft magnetic properties.
The investigation has dealt with the structure and magnetic properties of rapidly solidified and annealed Fe73.5−𝑥Si13.5B9Nb3Cu1Al𝑥 (𝑥 = 0, 2, 4, 6 at%) ribbons prepared by melt spinning. Complete amorphous structure was obtained in as-spun ribbons of 𝑥 = 0 and 2 at% compositions, whereas structure of ribbons containing higher Al was found to be partially crystalline. Detailed thermal analyses of the alloys and the melt spun ribbons revealed that the glass forming ability in the form of 𝑇x/𝑇l (ratio between crystallization and liquidus temperature) is the highest for 2 at% Al alloys and decreases with further addition of Al. Annealing of all as spun ribbons resulted in the precipitation of nanocrystalline phase embedded in amorphous matrix in the form of either 𝐷𝑂3 phase or 𝑏𝑐𝑐 𝛼-Fe(Si/Al) solid solution depending on the initial composition of the alloy. Only 𝑏𝑐𝑐 𝛼-Fe(Si/Al) solid solution was formed in 2 at% Al ribbons whereas ordered DO3 structure was found to be stabilized in other ribbons including 0 at% Al. A detailed study on determination of precision lattice parameter of nanocrystalline phase revealed that the lattice parameter increases with the addition of Al indicating the partitioning behaviour of Al in nanocrystalline phase.