Ordering and phase separation in the b.c.c. phase of the Fe-Al-Ti system

I. Ohnuma; C. G. Schön; R. Kainuma; G. Inden; K. Ishida

doi:10.1016/S1359-6454(97)00376-5

Ordering and phase separation in the b.c.c. phase of the Fe-Al-Ti system

I. Ohnuma, C. G. Schön, R. Kainuma, G. Inden, K. Ishida

ENG - Metallurgy

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Abstract

Ordering and phase separation in α-Fe alloys of the Fe-Al-Ti system have been investigated by differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and electron-probe microanalysis (EPMA). The results indicate that the partial replacement of Fe with Ti in the Fe-rich Fe-Al binary alloys results in drastically stabilizing the B2 (FeAl) and D0₃ (Fe₃Al) phases and increasing the A2-B2-D0₃ successive order-disorder transition temperatures. It is confirmed that there are two kinds of phase separations of the BCC phase, (A2 + D0₃) and (B2 + D0₃) in the composition range below 25 at.%Al. The width of the two-phase region drastically increases with decreasing Al composition. The two-phase regions close at ternary tricritical points. Calculations of BCC phase equilibria have been performed with the cluster variation method (CVM) using the irregular tetrahedron approximation. First and second nearest pair interactions as well as tetrahedron interactions are taken into account. Starting from binary and ternary phase equilibria the numerical values of these interactions have been determined and an excellent agreement between calculation and experiments was obtained.

Original language	English
Pages (from-to)	2083-2094
Number of pages	12
Journal	Acta Materialia
Volume	46
Issue number	6
DOIs	https://doi.org/10.1016/S1359-6454(97)00376-5
Publication status	Published - 1998 Mar 23

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title = "Ordering and phase separation in the b.c.c. phase of the Fe-Al-Ti system",

abstract = "Ordering and phase separation in α-Fe alloys of the Fe-Al-Ti system have been investigated by differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and electron-probe microanalysis (EPMA). The results indicate that the partial replacement of Fe with Ti in the Fe-rich Fe-Al binary alloys results in drastically stabilizing the B2 (FeAl) and D03 (Fe3Al) phases and increasing the A2-B2-D03 successive order-disorder transition temperatures. It is confirmed that there are two kinds of phase separations of the BCC phase, (A2 + D03) and (B2 + D03) in the composition range below 25 at.%Al. The width of the two-phase region drastically increases with decreasing Al composition. The two-phase regions close at ternary tricritical points. Calculations of BCC phase equilibria have been performed with the cluster variation method (CVM) using the irregular tetrahedron approximation. First and second nearest pair interactions as well as tetrahedron interactions are taken into account. Starting from binary and ternary phase equilibria the numerical values of these interactions have been determined and an excellent agreement between calculation and experiments was obtained.",

author = "I. Ohnuma and Sch{\"o}n, {C. G.} and R. Kainuma and G. Inden and K. Ishida",

note = "Funding Information: This work was supported by the Grant-in-Aids for Scientific Research from the Ministry of Education, Science, Sports and Culture, Japan. The authors acknowledge the support from the TEPCO Research Foundation. C. G. S. gratefully acknowledges the support of the German Academic Exchange Office (DAAD) under grant no. A/93/17173.",

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T1 - Ordering and phase separation in the b.c.c. phase of the Fe-Al-Ti system

AU - Ohnuma, I.

AU - Schön, C. G.

AU - Kainuma, R.

AU - Inden, G.

AU - Ishida, K.

N1 - Funding Information: This work was supported by the Grant-in-Aids for Scientific Research from the Ministry of Education, Science, Sports and Culture, Japan. The authors acknowledge the support from the TEPCO Research Foundation. C. G. S. gratefully acknowledges the support of the German Academic Exchange Office (DAAD) under grant no. A/93/17173.

PY - 1998/3/23

Y1 - 1998/3/23

N2 - Ordering and phase separation in α-Fe alloys of the Fe-Al-Ti system have been investigated by differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and electron-probe microanalysis (EPMA). The results indicate that the partial replacement of Fe with Ti in the Fe-rich Fe-Al binary alloys results in drastically stabilizing the B2 (FeAl) and D03 (Fe3Al) phases and increasing the A2-B2-D03 successive order-disorder transition temperatures. It is confirmed that there are two kinds of phase separations of the BCC phase, (A2 + D03) and (B2 + D03) in the composition range below 25 at.%Al. The width of the two-phase region drastically increases with decreasing Al composition. The two-phase regions close at ternary tricritical points. Calculations of BCC phase equilibria have been performed with the cluster variation method (CVM) using the irregular tetrahedron approximation. First and second nearest pair interactions as well as tetrahedron interactions are taken into account. Starting from binary and ternary phase equilibria the numerical values of these interactions have been determined and an excellent agreement between calculation and experiments was obtained.

AB - Ordering and phase separation in α-Fe alloys of the Fe-Al-Ti system have been investigated by differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and electron-probe microanalysis (EPMA). The results indicate that the partial replacement of Fe with Ti in the Fe-rich Fe-Al binary alloys results in drastically stabilizing the B2 (FeAl) and D03 (Fe3Al) phases and increasing the A2-B2-D03 successive order-disorder transition temperatures. It is confirmed that there are two kinds of phase separations of the BCC phase, (A2 + D03) and (B2 + D03) in the composition range below 25 at.%Al. The width of the two-phase region drastically increases with decreasing Al composition. The two-phase regions close at ternary tricritical points. Calculations of BCC phase equilibria have been performed with the cluster variation method (CVM) using the irregular tetrahedron approximation. First and second nearest pair interactions as well as tetrahedron interactions are taken into account. Starting from binary and ternary phase equilibria the numerical values of these interactions have been determined and an excellent agreement between calculation and experiments was obtained.

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Ordering and phase separation in the b.c.c. phase of the Fe-Al-Ti system

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