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Al–Cl Aluminum–Chlorine system
245
Al-Cl Aluminum-Chlorine system Chlorine, either as gas or as an easily decomposed compound (ZnCl2, A1C13, BC13, hexachloroethane, etc.) is used extensively to cleanse melts of aluminum and its alloys. Mixtures of chlorine with argon, helium, nitrogen and carbon monoxide are also used to obtain equivalent cleansing with less atmospheric pollution. The solid impurities in the melt are removed by a floating action and dissolved hydrogen diffuses into the chlorine bubble and is carried to the surface. Appreciable degassing also results from oxide removal, because the porous oxide may entrap large amounts of gas [1-29]. In this way melts containing only limited amounts of hydrogen (<0.1ml/100gr) can be produced [19,30-34]. Magnesium removal [13, 19, 23, 33, 35-36] is accomplished through the reaction 136b]: 6Mg + 3C12 + A 1 2 0 3 ^ 3(MgCl2. MgO) + Al If the amount of magnesium to be removed is relatively large (> 0.3% Mg), most nucleating impurities are also removed and the subsequent castings have a very coarse grain size. When S2C12 is used the reaction is [37]: 3Mg + S2C12— 2MgS + MgCl2 Cleansing of melts is also obtained with molten mixtures of chlorides such as NaCl, KC1, usually together with fluorides. A1203 readily dissolves in the molten salt mixture and is washed out of the melt. The gas entrapped in the oxide is also removed. Methods for the continuous cleansing have been devised [29]. The use of the reaction 3AlCl ^ 2A1 + A1C13 has been investigated repeatedly as a means of producing or refining aluminum [38—47b]. The use of A1C13 as a component of fused salts of electrolytic baths for the deposition and refining of aluminum has been investigated [48-50]. Additions of chlorine to inert gases used for the shielding in arc welding is claimed to produce better welds through oxide removal [51]. Absorption of chlorine on clean surfaces was investigated by [5 lb]. The monochloride AlCl (56.8% Cl) is stable in the vapor phase; upon cooling it decomposes into Al and A1C13 [52]. Values for the heat of formation of AlCl range from —20kJ/mole to —67kJ/mole [53-55], with a selected value of —49kJ/mole [56]. A value of 185kJ/mole was reported for the heat of sublimation [57]. Table 2.2 PROPERTIES OF A1C13 A N D A12C16
Property Boiling point Sublimation temp. Critical temp. Triple point Heat of formation A1C13 A2C16 A1C13 Heat of fusion A12C16 Heat of dissociation A12C16 Heat of vaporisation A12C16 Heat of sublimation A12C16
Value 432-437°K 453 °K 630 °K f 463 °K 1 \ 0.235 MN/m 2 J 700kJ/mole 1 300kJ/mole 37kJ/mole 72 kJ/mole 120kJ/mole 40kJ/mole HOkJ/mole
Ref. 61,62 58,61 63 61 54, 64, 65, 66 54, 65, 67 61 58,61 58,61 61 58,61,62
246 The existence of A1C12 (72.4% Cl) is not considered likely at low temperatures; its calculated heat of formation is — 330kJ/mole [56, 57]. A1C13 (79.8% Cl) is mostly dimeric in the vapor state, the percentage of the monomeric form in the vapor near the boiling point of 450 °K being 0.02% [58]. For data on its thermal properties see Table 2.2. A1C13 is monoclinic; lattice parameters a = 5.92 x 10- 1 0 m, b= 10.22 x 10- 1 0 m, c = 6.16 x 10- 1 0 m, ß= 1 0 8 ° ; 16 atoms to the unit cell; space group C2/m [59, 60].
REFERENCES
1.
2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 28b. 28c. 28d. 28e. 28f. 29. 30. 31. 32. 33. 34. 35. 35b. 36. 36b. 37. 38. 39. 40. 41.
D.R.Tullis,//M39,510
W. Rosenhain, etc., /. Inst. Metals, 1930,44, 305 W. Koch, Metallwirtschaft, 1931,10,69 D. R. Tullis, JIM 47, 604; JIMMA 3, 570 E.Zielinski, 0 4 28,437 H. Bohner, Metall Erz, 1933, 30, 334 L. I. Dmitriev, JIMMA 5, 837; 7, 266 W. O. Kroenig, etc., JIMMA 5, 224 R. De Fleury, JIMMA 16, 88 G. W. Birdsall, CA 41, 5828 L. M. Grand, JIMMA 16, 85, 169 W. Kotte, etc., JIMMA 17, 949 W.Dautzenberg,.//MM4 18,439; 19, 227; 20, 911; 21, 55 T. Morinaga, etc., JIMMA 22, 701 A. W. Brace, JIMMA 20, 653, 903 W. Buchen, JIMMA 21, 639 K. E. Mann, JIMMA 21, 639 G. S. Enikeev, JIMMA 25, 625 G. D. Denyer, JIMMA 30, 753 V. P. Ivanov, etc., JIMMA 31, 757, 762 H. Ginsberg, etc., MA 1, 131; 2, 1290 K. O. Hornung, MA 2, 296 B. Lagowski, Met A 3, 510247 A. A. Ostapenko, etc., Met A 2, 510842 G. A. Deryagin, etc., Met A 3,430111 G. M. Kinstach, etc., Met A 4,430025 J. T. Olea, Met A 4,430036 G. Bracale, etc., Met A 3,460068 A. J. Copeland, etc., Met A 5,430193 R. J. Adamo, etc., Met A 5,430192; 6,460006 W. Thury, etc., Met A 6, 460021 P. Presche, Met A 6, 560276 L. C. Blayden, etc., WAA 7, 310042 M. V. Brant, etc., Met A 3,430139 W. Bunk, etc., Met A 2, 130301 H. Yamada,etc.,MeM 3,430126 L. Szabo, Met A 4, 510071 K. O. Hornung, Met A 3,430185 Y. P. Pimenov, etc., Met A 4,440264 Schneider, etc., JIMMA 18, 52 E. Gerdes, etc., Met A 6,430104 H. Scheuten, JIMMA 26, 1092 F. A. Crossley, Thesis, 111. Inst. Tech., Chicago, 1947 A. Domony, etc., JIMMA 20, 361 W. Klemm, etc., Z. Anorg. Allgem. Chem., 1943, 251, 233 P. Weiss, etc., JIMMA 18, 382 L. M. Foster, etc., JIMMA 18, 2 R. Heimgartner, JIMMA 21, 91
247
42. 43. 44. 45. 46. 47. 47b. 48. 49. 50. 51. 51b. 52. 53. 54. 55. 56. 57. 58. 59. 60. 61. 62. 63. 64. 65. 66. 67.
P. Gross, etc., JIMMA 23,474 W. Hirschwald, etc., CA 52,9730 A. I. Belyaev, etc., JIMMA 26, 865 L. A. Yerkes, etc., JIMMA 29, 847 H. Mitani, etc., Met A 1, 150488; 4,430030 T. Kikuchi, etc., Met A 2,440225; 6,440198, 440199, 440200 H. Nagai, etc., WAA 6, 240006, 240007 V. A. Plotnikov, etc., JIMMA 2,451 ; 3, 249; 5,299 K. M. Gorbunova, etc., CA 28,4984 J. Czochralski, etc., JIMMA 3, 557 M. B. Kasen, etc., JIMMA 26, 725 T. Smith, Met A 6, 340201 P. Gross, etc., JIMMA 17, 517; 18, 146 M. Heise, etc., CA 46, 7874 D. Rossini, etc., US Nat. Bur. Stds., Circ. 500, 1952 S. A. Semenkovich, CA 54, 19252 JANAF, Thermochemical Tables, Dow Chemical Co., Midland, Michigan, 1960 F. Irmann, CA 44,430 W. Fisher, etc., Z. Anorg. Allgem. Chem., 1932, 205, 37 J. A. A. Ketelaar, etc., CA 42,434 J. D. Corbett, etc., /. Am. Chem. Soc, 1953, 75, 5238 A. Smits, etc., CA 33, 69 T. G. Dunne, etc., CA 52, 13352 Z. Rotinjanz, etc., Z. Physik. Chem., 1914,87, 635 A. Roth, etc., Z. Elektrochem., 1934,40, 89 R. R. Bichowsky, etc., The Thermochemistry of the Chemical Substances, Reinhold, 1936 H. Siemonsen, CA 45, 7864 W. D. Treadwell, etc., CA 29, 2065
Al-Co Aluminum-Cobalt system In alloys containing more than 5% Si, cobalt is superior to other iron correctors such as manganese and chromium because it does not form compounds with silicon; but present practice has been to reduce the iron content rather than correct it. The unidirectionally solidified eutectic as a fiber reinforced material has been investigated by [1-2]. At the aluminum end there is a eutectic, liq.—> Al + Co2Al9, at approximately 1% Co, 930 °K; the solid solubility is less than 0.02% Co at eutectic temperature, and probably decreases with decreasing temperature [3, 4] (Figure 2.15). By fast quenching from the liquid up to 6.5% Co can be held in solution and the lattice parameter decreases to 4.024 x l 0 ~ 1 0 m [5-7]. For thermodynamic properties see [7b]. Co2Al9 (32.7% Co) is monoclinic; space group P2jc\ 22 atoms in the unit cell; parameters a = 6.213xl0- 1 0 m, 6 = 6.29xl0- 1 0 m, c=8.556 5x 10- 10 m, ß = 94° 16' [7c, 8]. The crystal structure fits the accepted formula but crystals separated from aluminum-rich alloys average 33.25% Co, closer to Co3Al13 [9, 9b]. Co2Al9 has a density of 3 670kg/m3 [10]; Vickers hardness at room temperature of 6 500-7 500MN/m 2 [11], which does not change appreciably up to 700°K [12]. The heat of formation is 30kJ/gr-at [13]. For data on the electronic structure of Co2Al9 see also [13b, 14], and for optical properties see [15, 16]. AASP—9
Al-Cl Aluminum-Chlorine system Chlorine, either as gas or as an easily decomposed compound (ZnCl2, A1C13, BC13, hexachloroethane, etc.) is used extensively to cleanse melts of aluminum and its alloys. Mixtures of chlorine with argon, helium, nitrogen and carbon monoxide are also used to obtain equivalent cleansing with less atmospheric pollution. The solid impurities in the melt are removed by a floating action and dissolved hydrogen diffuses into the chlorine bubble and is carried to the surface. Appreciable degassing also results from oxide removal, because the porous oxide may entrap large amounts of gas [1-29]. In this way melts containing only limited amounts of hydrogen (<0.1ml/100gr) can be produced [19,30-34]. Magnesium removal [13, 19, 23, 33, 35-36] is accomplished through the reaction 136b]: 6Mg + 3C12 + A 1 2 0 3 ^ 3(MgCl2. MgO) + Al If the amount of magnesium to be removed is relatively large (> 0.3% Mg), most nucleating impurities are also removed and the subsequent castings have a very coarse grain size. When S2C12 is used the reaction is [37]: 3Mg + S2C12— 2MgS + MgCl2 Cleansing of melts is also obtained with molten mixtures of chlorides such as NaCl, KC1, usually together with fluorides. A1203 readily dissolves in the molten salt mixture and is washed out of the melt. The gas entrapped in the oxide is also removed. Methods for the continuous cleansing have been devised [29]. The use of the reaction 3AlCl ^ 2A1 + A1C13 has been investigated repeatedly as a means of producing or refining aluminum [38—47b]. The use of A1C13 as a component of fused salts of electrolytic baths for the deposition and refining of aluminum has been investigated [48-50]. Additions of chlorine to inert gases used for the shielding in arc welding is claimed to produce better welds through oxide removal [51]. Absorption of chlorine on clean surfaces was investigated by [5 lb]. The monochloride AlCl (56.8% Cl) is stable in the vapor phase; upon cooling it decomposes into Al and A1C13 [52]. Values for the heat of formation of AlCl range from —20kJ/mole to —67kJ/mole [53-55], with a selected value of —49kJ/mole [56]. A value of 185kJ/mole was reported for the heat of sublimation [57]. Table 2.2 PROPERTIES OF A1C13 A N D A12C16
Property Boiling point Sublimation temp. Critical temp. Triple point Heat of formation A1C13 A2C16 A1C13 Heat of fusion A12C16 Heat of dissociation A12C16 Heat of vaporisation A12C16 Heat of sublimation A12C16
Value 432-437°K 453 °K 630 °K f 463 °K 1 \ 0.235 MN/m 2 J 700kJ/mole 1 300kJ/mole 37kJ/mole 72 kJ/mole 120kJ/mole 40kJ/mole HOkJ/mole
Ref. 61,62 58,61 63 61 54, 64, 65, 66 54, 65, 67 61 58,61 58,61 61 58,61,62
246 The existence of A1C12 (72.4% Cl) is not considered likely at low temperatures; its calculated heat of formation is — 330kJ/mole [56, 57]. A1C13 (79.8% Cl) is mostly dimeric in the vapor state, the percentage of the monomeric form in the vapor near the boiling point of 450 °K being 0.02% [58]. For data on its thermal properties see Table 2.2. A1C13 is monoclinic; lattice parameters a = 5.92 x 10- 1 0 m, b= 10.22 x 10- 1 0 m, c = 6.16 x 10- 1 0 m, ß= 1 0 8 ° ; 16 atoms to the unit cell; space group C2/m [59, 60].
REFERENCES
1.
2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 28b. 28c. 28d. 28e. 28f. 29. 30. 31. 32. 33. 34. 35. 35b. 36. 36b. 37. 38. 39. 40. 41.
D.R.Tullis,//M39,510
W. Rosenhain, etc., /. Inst. Metals, 1930,44, 305 W. Koch, Metallwirtschaft, 1931,10,69 D. R. Tullis, JIM 47, 604; JIMMA 3, 570 E.Zielinski, 0 4 28,437 H. Bohner, Metall Erz, 1933, 30, 334 L. I. Dmitriev, JIMMA 5, 837; 7, 266 W. O. Kroenig, etc., JIMMA 5, 224 R. De Fleury, JIMMA 16, 88 G. W. Birdsall, CA 41, 5828 L. M. Grand, JIMMA 16, 85, 169 W. Kotte, etc., JIMMA 17, 949 W.Dautzenberg,.//MM4 18,439; 19, 227; 20, 911; 21, 55 T. Morinaga, etc., JIMMA 22, 701 A. W. Brace, JIMMA 20, 653, 903 W. Buchen, JIMMA 21, 639 K. E. Mann, JIMMA 21, 639 G. S. Enikeev, JIMMA 25, 625 G. D. Denyer, JIMMA 30, 753 V. P. Ivanov, etc., JIMMA 31, 757, 762 H. Ginsberg, etc., MA 1, 131; 2, 1290 K. O. Hornung, MA 2, 296 B. Lagowski, Met A 3, 510247 A. A. Ostapenko, etc., Met A 2, 510842 G. A. Deryagin, etc., Met A 3,430111 G. M. Kinstach, etc., Met A 4,430025 J. T. Olea, Met A 4,430036 G. Bracale, etc., Met A 3,460068 A. J. Copeland, etc., Met A 5,430193 R. J. Adamo, etc., Met A 5,430192; 6,460006 W. Thury, etc., Met A 6, 460021 P. Presche, Met A 6, 560276 L. C. Blayden, etc., WAA 7, 310042 M. V. Brant, etc., Met A 3,430139 W. Bunk, etc., Met A 2, 130301 H. Yamada,etc.,MeM 3,430126 L. Szabo, Met A 4, 510071 K. O. Hornung, Met A 3,430185 Y. P. Pimenov, etc., Met A 4,440264 Schneider, etc., JIMMA 18, 52 E. Gerdes, etc., Met A 6,430104 H. Scheuten, JIMMA 26, 1092 F. A. Crossley, Thesis, 111. Inst. Tech., Chicago, 1947 A. Domony, etc., JIMMA 20, 361 W. Klemm, etc., Z. Anorg. Allgem. Chem., 1943, 251, 233 P. Weiss, etc., JIMMA 18, 382 L. M. Foster, etc., JIMMA 18, 2 R. Heimgartner, JIMMA 21, 91
247
42. 43. 44. 45. 46. 47. 47b. 48. 49. 50. 51. 51b. 52. 53. 54. 55. 56. 57. 58. 59. 60. 61. 62. 63. 64. 65. 66. 67.
P. Gross, etc., JIMMA 23,474 W. Hirschwald, etc., CA 52,9730 A. I. Belyaev, etc., JIMMA 26, 865 L. A. Yerkes, etc., JIMMA 29, 847 H. Mitani, etc., Met A 1, 150488; 4,430030 T. Kikuchi, etc., Met A 2,440225; 6,440198, 440199, 440200 H. Nagai, etc., WAA 6, 240006, 240007 V. A. Plotnikov, etc., JIMMA 2,451 ; 3, 249; 5,299 K. M. Gorbunova, etc., CA 28,4984 J. Czochralski, etc., JIMMA 3, 557 M. B. Kasen, etc., JIMMA 26, 725 T. Smith, Met A 6, 340201 P. Gross, etc., JIMMA 17, 517; 18, 146 M. Heise, etc., CA 46, 7874 D. Rossini, etc., US Nat. Bur. Stds., Circ. 500, 1952 S. A. Semenkovich, CA 54, 19252 JANAF, Thermochemical Tables, Dow Chemical Co., Midland, Michigan, 1960 F. Irmann, CA 44,430 W. Fisher, etc., Z. Anorg. Allgem. Chem., 1932, 205, 37 J. A. A. Ketelaar, etc., CA 42,434 J. D. Corbett, etc., /. Am. Chem. Soc, 1953, 75, 5238 A. Smits, etc., CA 33, 69 T. G. Dunne, etc., CA 52, 13352 Z. Rotinjanz, etc., Z. Physik. Chem., 1914,87, 635 A. Roth, etc., Z. Elektrochem., 1934,40, 89 R. R. Bichowsky, etc., The Thermochemistry of the Chemical Substances, Reinhold, 1936 H. Siemonsen, CA 45, 7864 W. D. Treadwell, etc., CA 29, 2065
Al-Co Aluminum-Cobalt system In alloys containing more than 5% Si, cobalt is superior to other iron correctors such as manganese and chromium because it does not form compounds with silicon; but present practice has been to reduce the iron content rather than correct it. The unidirectionally solidified eutectic as a fiber reinforced material has been investigated by [1-2]. At the aluminum end there is a eutectic, liq.—> Al + Co2Al9, at approximately 1% Co, 930 °K; the solid solubility is less than 0.02% Co at eutectic temperature, and probably decreases with decreasing temperature [3, 4] (Figure 2.15). By fast quenching from the liquid up to 6.5% Co can be held in solution and the lattice parameter decreases to 4.024 x l 0 ~ 1 0 m [5-7]. For thermodynamic properties see [7b]. Co2Al9 (32.7% Co) is monoclinic; space group P2jc\ 22 atoms in the unit cell; parameters a = 6.213xl0- 1 0 m, 6 = 6.29xl0- 1 0 m, c=8.556 5x 10- 10 m, ß = 94° 16' [7c, 8]. The crystal structure fits the accepted formula but crystals separated from aluminum-rich alloys average 33.25% Co, closer to Co3Al13 [9, 9b]. Co2Al9 has a density of 3 670kg/m3 [10]; Vickers hardness at room temperature of 6 500-7 500MN/m 2 [11], which does not change appreciably up to 700°K [12]. The heat of formation is 30kJ/gr-at [13]. For data on the electronic structure of Co2Al9 see also [13b, 14], and for optical properties see [15, 16]. AASP—9