Structural and Magnetic Properties of Unidirectionally Solidified Fe-Fe₂Ti Eutectic Alloys

Abstract

Structures and magnetic properties of Fe-Fe₂Ti eutectic alloys containing 11, 16 and 18 wt%Ti respectively and those of unidirectionally solidified Fe-16 wt%Ti alloy have been investigated.
As the result of magnetic analysis, Fe-Fe₂Ti eutectic alloys consists of two ferromagnetic α-Fe andFe_2+xTi_1-x phases (λ>0). The Curie temperature of the former is 780°C and that of the latter is around 100-135°C, depending on Ti content in alloys and heat treatment condition. It seems that the Ti content of Fe_2+xTi_1-x; in Fe-Fe_2+xTi_1-x eutectic alloys, annealed at 1 000°C for 1 hour, is around 29 at% by magnetic measurement.
The structure of unidirectionally solidified Fe-16 wt%Ti alloy has the lamellar or rod-like Fe_2+xTi_1-x phase in matrix of α-Fe phase. The results of metallography, X-ray diffraction and powder patterns indicate that a great part of ‹0001› of Fe_2+x, Ti_1-x phase and ‹100› of α-Fe phase are parallel to the crystal growth direction on the crystallographic orientations of both phases. Similarly, the magnetic properties of unidirectionally solidified alloy show anisotropy depending on solidification rates. The magnetic anisotropy for this unidirectionally solidified eutectic alloy may be mainly caused by crystal anisotropy of Fe_2+xTi_1-x phase and shape anisotropy of α-Fe phase by magnetic torque measurement up to 285°C.