- Email: [email protected]
Al–Cu–Li Aluminum–Copper–Lithium system
495 width of the precipitate-free zone at the grain boundaries [7J. An acceleration of the 6 phase formation is reported by [8]. The sequence of structures during the aging is the same as in aluminum-copper-cadmium alloys: two unexplained structures are formed together with θ', which are then superseded by In' (intermediate phase in the precipitation of indium from aluminum) [1]. Heat evolution due to the formation of these structures has been detected [9]. REFERENCES 1. 2. 3. 4. 5. 6. 7. 8. 9.
V. M. Silcock, etc., JIMMÄ 23, 111; 27, 559 W. H. Fraenkel, JIMMA 9, 118 H. K. Hardy, JIMMA 21, 603; 23, 1081 K. M. Entwistle, etc., JIMMA 30, 373 A. J. Perry, etc., Met A 2, 140145 B. Noble, Met A 1, 140204, 140223 J. B. M. Nuyten, Met A 3, 140003 S. Matsuo, etc., Met A 2, 151237 T. Hirata, etc., Met A 5, 140116
Al-Cu-La Aluminum-Copper-Lanthanum system There are several ternary compounds in this system, two of which, Cu2LaAl10 and La(CuAl)4, are in equilibrium with aluminum. Cu2LaAl10 (23.4% Cu, 26.0% La) is body centered tetragonal; space group I4/mmm; 26 atoms to the unit cell; parameters a = 8.8 x 10~10m, c = 5.17 x 10 _10 m. La(CuAl)4, whose composition ranges from CuLa2Al7 (11.9% Cu, 52.5% La) to CuLaAl3 (22.4% Cu, 49.1% La), is also body centered tetragonal; space group I4/mmm; 10 atoms in the unit cell; parameters a = 4.326-4.294 xl0- 1 0 m, c= 10.80-10.53 x 10- 10 m [1]. REFERENCE 1. O. S. Zarechnyuk, etc., Met A 2, 121215
Al-Cu-Li Aluminum-Copper—Lithium system In the aluminum corner of the diagram there are three ternary compounds in equilibrium with aluminum, named TB, T1? T2. Two other phases lower in aluminum content were also discovered. The TB phase has a composition close to 55 - 57% Cu, 1.1-1.5% Li, corresponding to the formula Cu4LiAl7 (56.5% Cu, 1.5% Li). It is cubic; space group Fm3m; 12 atoms in the unit cell; parameter a = 5.83 x 10"10m; density
496 3 640-3 760kg/m3. Its structure is very similar to that of the 0'(CuAl2) intermediate phase formed in age hardening in aluminum-copper alloys [1], and could be a form of it, stabilised by replacement of some aluminum atoms by lithium. It has a Vickers hardness of 4 250-4 750MN/m 2 , which does not decrease substantially until above 600°K [2]. The Tj phase contains approximately 52.8% Cu,_5.4% Li, close to the formula CuLiAl2. It is hexagonal; possible space groups P6 2 2, P6m2, P6/mmm; lattice parameters a = 4.96-4.955 x 10- 10 m, c = 9.34-9.35 x 10- 10 m; Vickers hardness 4 250-5 200MN/m 2 [2]. The T2 phase has a composition close to that of the CuLi3Al6 (26.9% Cu, 8.8% Li) [1] and a Vickers hardness of 3 200-3 700MN/m 2 . This phase is more probably CuLi3Al5 (28.8% Cu, 9.6% Li); cubic; space group Im3\ 162 atoms to the unit cell; lattice parameter a= 13.914 x 10 _10 m; isomorphous with Mg32 (ZnAl)49 [3]. The LiAl compound can dissolve small amounts of copper, with a slight shrinkage of its lattice. The distribution of phases in the solid state is shown in Figure 3.18 at 800 and 600 °K.
Al
2
4 Wt.96Cu
6
8
Figure 3.18. Aluminum corner of the aluminum-copper-lithium diagram; phase distribution at 775 °K (solid lines) and 600 °K (dashed lines) Lithium reduces sharply the liquid-gas surface tension of aluminum-copper alloys [4]. Alloys containing 2% Cu and 1-2% Li have reasonably high mechanical properties (UTS = 350MN/m 2 , £ = 2 - 3 % ) in the fully aged condition, and cold working before aging raises the ultimate tensile strength to almost 500MN/m 2 , with E = 1% [5]. However, in the alloys containing 4-5% Cu with 0.5-1.5% Li and additions of manganese and cadmium, higher mechanical properties can be obtained. Corrosion resistance of the commercial alloys is comparable with that of the aluminum-copper-magnesium type alloys. As in most age hardenable alloys, susceptibility to stress corrosion is very low when aged slightly past peak strength, very high if under-aged [6]. In aging at temperatures below 325 °K the GP zones contain only copper atoms; at 350-400 °K, on the other hand, lithium atoms also collect into the zones [7]. Further aging produces the Θ" and θ' of the aluminum-copper alloys together with the δ' of the aluminum-lithium alloys. No intermediate phases for the ternary compounds were
497 detected 18, 9], possibly because they are very similar to the binary ones. At higher aging temperatures the Ύλ phase forms as hexagonal plates on (111) planes, with orientation relationship [7, 10]: (110) Tl ||(lll) A1 ,
(100)Tl||(110)A1
and
[110]Tl||[211]A1
At low supersaturation the Tl phase nucleates on stacking faults; at higher supersaturations probably on the GP zones [7]. The TTT curve for an alloy of 4.5% Cu, 0.8% Li, 0.6% Mn, 0.3% Cd shows activation energies of the order of 0.4eV for the beginning of aging and the attainment of the first peak and 1.2 eV for the start and attainment of the second peak [6]. Deformation by twinning was detected [10]. REFERENCES 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.
H. K. Hardy, etc., JIMMA 23, 1081 Z. A. Sviderskaya, etc., JIMMA 30,498 E. E. Cherkashin, etc., JIMMA 32, 1112 L. Kubichek, JIMMA 27, 629 W. R. D. Jones, etc., JIMMA 27, 715 K. Anderko, etc., JIMMA 30, 90 B. Noble, etc., Met A 3, 130737; 6, 140021, 330539 J. M. Silcock, JIMMA 27, 559 K. Schneider, etc., Met A 7, 140063, 140083 O. S. Bochvar, etc., CA 78, 7064t, 61293e
Al-Cu-Mg Aluminum-Copper-Magnesium system The aluminum end of the diagram has been repeatedly investigated and a good review of the literature is available [1]. The liquidus surfaces at the aluminum end are shown in Figure 3.19'; the invariant reactions in Table 3.17. The ternary reaction at the magnesium side is also given as liq. + CuMg4Al6—>Al + Mg5Al8, at 725 °K [2]. The eutectic Al-CuMgAl 2 is quasibinary, but the section Al-CuMgAl 2 cannot be considered a truly quasibinary one. Crystallisation of the alloys on the monovariant line from the eutectic Al-CuAl 2 to the Al-CuMgAl 2 has been investigated by [3]. Table 3.17 INVARIANT REACTIONS AT THE ALUMINUM CORNER OF THE ALUMINUM-COPPER-MAGNESIUM SYSTEM [1]
Reaction (A) liq.— Al + CuAl2 (B) liq.— Al + CuAl2 + CuMgAl2 (C) liq.—Al + CuMgAl2 (quasibinary) (D) liq. + CuMgAl2— Al + CuMg4Al6 (E) liq.— CuMg4Al6 + Al + Mg3Al8 (F) liq.— AH-Mg5Al8
Temperature
Composition
(°K)
(°F)
%Cu
%Mg
821 780 791
1018 944 964
33.2 30 24.5
0 6 10.1
740 722 723
872 840 842
10 2.7 0
26 32 34
V. M. Silcock, etc., JIMMÄ 23, 111; 27, 559 W. H. Fraenkel, JIMMA 9, 118 H. K. Hardy, JIMMA 21, 603; 23, 1081 K. M. Entwistle, etc., JIMMA 30, 373 A. J. Perry, etc., Met A 2, 140145 B. Noble, Met A 1, 140204, 140223 J. B. M. Nuyten, Met A 3, 140003 S. Matsuo, etc., Met A 2, 151237 T. Hirata, etc., Met A 5, 140116
Al-Cu-La Aluminum-Copper-Lanthanum system There are several ternary compounds in this system, two of which, Cu2LaAl10 and La(CuAl)4, are in equilibrium with aluminum. Cu2LaAl10 (23.4% Cu, 26.0% La) is body centered tetragonal; space group I4/mmm; 26 atoms to the unit cell; parameters a = 8.8 x 10~10m, c = 5.17 x 10 _10 m. La(CuAl)4, whose composition ranges from CuLa2Al7 (11.9% Cu, 52.5% La) to CuLaAl3 (22.4% Cu, 49.1% La), is also body centered tetragonal; space group I4/mmm; 10 atoms in the unit cell; parameters a = 4.326-4.294 xl0- 1 0 m, c= 10.80-10.53 x 10- 10 m [1]. REFERENCE 1. O. S. Zarechnyuk, etc., Met A 2, 121215
Al-Cu-Li Aluminum-Copper—Lithium system In the aluminum corner of the diagram there are three ternary compounds in equilibrium with aluminum, named TB, T1? T2. Two other phases lower in aluminum content were also discovered. The TB phase has a composition close to 55 - 57% Cu, 1.1-1.5% Li, corresponding to the formula Cu4LiAl7 (56.5% Cu, 1.5% Li). It is cubic; space group Fm3m; 12 atoms in the unit cell; parameter a = 5.83 x 10"10m; density
496 3 640-3 760kg/m3. Its structure is very similar to that of the 0'(CuAl2) intermediate phase formed in age hardening in aluminum-copper alloys [1], and could be a form of it, stabilised by replacement of some aluminum atoms by lithium. It has a Vickers hardness of 4 250-4 750MN/m 2 , which does not decrease substantially until above 600°K [2]. The Tj phase contains approximately 52.8% Cu,_5.4% Li, close to the formula CuLiAl2. It is hexagonal; possible space groups P6 2 2, P6m2, P6/mmm; lattice parameters a = 4.96-4.955 x 10- 10 m, c = 9.34-9.35 x 10- 10 m; Vickers hardness 4 250-5 200MN/m 2 [2]. The T2 phase has a composition close to that of the CuLi3Al6 (26.9% Cu, 8.8% Li) [1] and a Vickers hardness of 3 200-3 700MN/m 2 . This phase is more probably CuLi3Al5 (28.8% Cu, 9.6% Li); cubic; space group Im3\ 162 atoms to the unit cell; lattice parameter a= 13.914 x 10 _10 m; isomorphous with Mg32 (ZnAl)49 [3]. The LiAl compound can dissolve small amounts of copper, with a slight shrinkage of its lattice. The distribution of phases in the solid state is shown in Figure 3.18 at 800 and 600 °K.
Al
2
4 Wt.96Cu
6
8
Figure 3.18. Aluminum corner of the aluminum-copper-lithium diagram; phase distribution at 775 °K (solid lines) and 600 °K (dashed lines) Lithium reduces sharply the liquid-gas surface tension of aluminum-copper alloys [4]. Alloys containing 2% Cu and 1-2% Li have reasonably high mechanical properties (UTS = 350MN/m 2 , £ = 2 - 3 % ) in the fully aged condition, and cold working before aging raises the ultimate tensile strength to almost 500MN/m 2 , with E = 1% [5]. However, in the alloys containing 4-5% Cu with 0.5-1.5% Li and additions of manganese and cadmium, higher mechanical properties can be obtained. Corrosion resistance of the commercial alloys is comparable with that of the aluminum-copper-magnesium type alloys. As in most age hardenable alloys, susceptibility to stress corrosion is very low when aged slightly past peak strength, very high if under-aged [6]. In aging at temperatures below 325 °K the GP zones contain only copper atoms; at 350-400 °K, on the other hand, lithium atoms also collect into the zones [7]. Further aging produces the Θ" and θ' of the aluminum-copper alloys together with the δ' of the aluminum-lithium alloys. No intermediate phases for the ternary compounds were
497 detected 18, 9], possibly because they are very similar to the binary ones. At higher aging temperatures the Ύλ phase forms as hexagonal plates on (111) planes, with orientation relationship [7, 10]: (110) Tl ||(lll) A1 ,
(100)Tl||(110)A1
and
[110]Tl||[211]A1
At low supersaturation the Tl phase nucleates on stacking faults; at higher supersaturations probably on the GP zones [7]. The TTT curve for an alloy of 4.5% Cu, 0.8% Li, 0.6% Mn, 0.3% Cd shows activation energies of the order of 0.4eV for the beginning of aging and the attainment of the first peak and 1.2 eV for the start and attainment of the second peak [6]. Deformation by twinning was detected [10]. REFERENCES 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.
H. K. Hardy, etc., JIMMA 23, 1081 Z. A. Sviderskaya, etc., JIMMA 30,498 E. E. Cherkashin, etc., JIMMA 32, 1112 L. Kubichek, JIMMA 27, 629 W. R. D. Jones, etc., JIMMA 27, 715 K. Anderko, etc., JIMMA 30, 90 B. Noble, etc., Met A 3, 130737; 6, 140021, 330539 J. M. Silcock, JIMMA 27, 559 K. Schneider, etc., Met A 7, 140063, 140083 O. S. Bochvar, etc., CA 78, 7064t, 61293e
Al-Cu-Mg Aluminum-Copper-Magnesium system The aluminum end of the diagram has been repeatedly investigated and a good review of the literature is available [1]. The liquidus surfaces at the aluminum end are shown in Figure 3.19'; the invariant reactions in Table 3.17. The ternary reaction at the magnesium side is also given as liq. + CuMg4Al6—>Al + Mg5Al8, at 725 °K [2]. The eutectic Al-CuMgAl 2 is quasibinary, but the section Al-CuMgAl 2 cannot be considered a truly quasibinary one. Crystallisation of the alloys on the monovariant line from the eutectic Al-CuAl 2 to the Al-CuMgAl 2 has been investigated by [3]. Table 3.17 INVARIANT REACTIONS AT THE ALUMINUM CORNER OF THE ALUMINUM-COPPER-MAGNESIUM SYSTEM [1]
Reaction (A) liq.— Al + CuAl2 (B) liq.— Al + CuAl2 + CuMgAl2 (C) liq.—Al + CuMgAl2 (quasibinary) (D) liq. + CuMgAl2— Al + CuMg4Al6 (E) liq.— CuMg4Al6 + Al + Mg3Al8 (F) liq.— AH-Mg5Al8
Temperature
Composition
(°K)
(°F)
%Cu
%Mg
821 780 791
1018 944 964
33.2 30 24.5
0 6 10.1
740 722 723
872 840 842
10 2.7 0
26 32 34