Masuo Hagiwara1, Jun-ichi Seki1 and Tomoo Suzuki2
1Graduate School, Tokyo Institute of Technology, Tokyo
The CsCl-type superlattice formation and the composition dependence of the order-disorder transition temperature (Tc) in V-Mn-Fe, Fe-V-Cr and V-Mn-Cr ternary alloys have been investigated by means of X-ray and differential thermal analysis. The results are summarized as follows.
(1) The Tc of the VMn superlattice is raised by the addition of Fe and is lowered by the addition of Cr.
(2) The Tc of the CsCl-type FeV superlattice is not known because of the intervention of the stable σ -phase. However, it has been found that the Tc can be detected by the addition of Cr which suppresses the formation of the σ -phase. The Tc decreases with the increase of Cr content.
(3) By extrapolating the measured Tc in V-Mn-Fe and Fe-V-Cr ternary alloys, the Tc of the equiatomic FeV superlattice has been estimated to be 850 ∼ 880°C.
(4) An anomaly similar to the ``550°C anomaly'' in α -FeCo and the ``730°C anomaly'' in δ -VMn has been considered to exist in the disordering process of the FeV superlattice.
(5) Based upon the measured Tc in the ternary alloys, a thermodynamic interaction parameter for the bcc phase of each binary system, constituting the ternary system, has been estimated, and this value has been compared with the existing data.
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