Ca-Fe (Calcium-Iron)
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ection III: Supplemental Literature Review
Ca-Fe (Calcium-Iron) H. Okamoto
The Ca-Fe phase diagram in [Massalski2] was redrawn from [1992Kah]. The Ca-Fe phase diagram near the Fe corner was reported by [1993Gla] partly based on [1960Kre] for the solubility of Ca in liquid Fe, as reviewed by [1994Oka]. This phase diagram is shown in Fig. 1. Formation of a c loop was concluded in this study. Solid lines in Fig. 2 show the Ca-Fe phase diagram reported by [1987Sch]. The Ca corner of this phase diagram is enlarged in Fig. 3. The (cFe) phase was not shown in the diagram of [1987Sch]. This can be explained by assuming that the c loop is so narrow that it is located within the line width of the pure Fe line. This is quantitatively consistent with the diagram of [1993Gla] (Fig. 1). However, the quantitative scale of Fig. 1 is questionable, as discussed below. Figure 4 shows the Fe corner of the Ca-Fe phase diagram calculated by [1994Ang]. The L1 + L2/L2 boundary was calculated based on the data of [1964Spo] and [1985Koh]. When Fig. 1 and 4 are compared, it is found
that discrepancy in the solubility of Ca in liquid Fe is about 100 times. It is more reasonable to assume that the scale in Fig. 1 is questionable because the six 9 purity in the horizontal axis is very uncommon. The (cFe) phase was missing in the diagram of [1987Sch], as described above. However, the van’t Hoff relationship demands certain initial angle for the (aFe)/ (aFe) + (cFe) boundary away from the 100% Fe line at both highest and lowest temperature limits (1394 and 912 °C). Because the L1 + (aFe)/(aFe) boundary is located very close to the 100% Fe line, the c loop must cross this boundary. The temperatures at the crossing should not be much different from the allotropic transformation temperatures of cFe. Two dashed lines have been added in Fig. 2 to reflect this situation. After all, the overall Ca-Fe phase diagram looks like the one proposed by [1992Kah], but the behavior of the (cFe) phase must be clarified (tends to form a c loop or not). Ca-Fe crystal structure data are given in Table 1.
Weight Percent Iron 99.9996
99.9997
99.9998
100
99.9999
1700
L2
1600 1500
Temperature, °C
1400 1300 1200
( Fe)
1100
L1 + ( Fe)
( Fe)
1000 900 800
( Ca) + ( Fe) 700 99.9994
99.9995
99.9996
99.9997
99.9998
99.9999
Atomic Percent Iron
Fig. 1 Fe corner of the Ca-Fe phase diagram [1993Gla] (composition scale may be wrong)
88
Journal of Phase Equilibria and Diffusion Vol. 31 No. 1 2010
100
Fe
Supplemental Literature Review: Section III Weight Percent Iron 2400
0
10
20
30
40
50
60
70
80
100
90
2200 2000
L2
1800
Temperature, °C
1600
( Fe)
1400 1200
L1
1538°C 1394°C
( Fe)
1000
912°C
842°C 800
( Fe)
( Ca)
600 443°C 400
( Ca)
200 0
10
0
20
30
40
50
60
70
80
90
Atomic % Iron
Ca
100
Fe
Fig. 2 Ca-Fe phase diagram [1987Sch]
Weight Percent Iron 0.05
0
0.10
0.15
0.20
0.25
0.30
1800 1700
L1 + L2
1600 1538°C
L1
Temperature, °C
1500
L1 + ( Fe) 1394°C
1400 1300 1200
L1 + ( Fe) 1100 1000 912°C
900 842
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