Abstract:The effects of melt overheating degree on the undercooling degree and resultant solidification structures of Nd₉Fe_85-xTi₄C₂B_x (x=10, 12) glass-forming alloys were studied by differential thermal analysis combining with solidification structure analysis. The results indicate that the undercooling degree of Nd₉Fe_85-xTi₄C₂B_x (x=10, 12) alloys significantly increases with the rise of melt overheating degree, and two overheating degree thresholds corresponding to the drastic increase of the mean undercooling degree are found for each of the alloys. The existence of two turning points of the mean undercooling degrees can be linked to the structure transitions inside the overheated melts, which result in the evident increase of volume fraction of amorphous phase in the solidified structures.

Key words: magnetic alloy; melt overheating; undercooling degree; structure transition; glass formability