- Email: [email protected]
Crystal structures of CuSnMg and Cu4SnMg ternary compounds
Journal of the Less-Common Metals, 60 (1978) 311 - 313 0 Elsevier Sequoia S.A., Lausanne - Printed in the Netherlands
311
Letter
Crystal structures KOZO OS~URA Department (Received
of CuSnMg and Cu,SnMg ternary and YOTARO
compounds
MURAKAMI
of Metallurgy, Kyoto University, 606 Kyoto (Japan)
March 20,1978)
Cu-Sn-Mg ternary alloys have recently been reported by some authors [l - 31 to show precipitation hardening, in which the heterogeneous precipitates on the grain boundary and the homogeneous precipitates in the matrix were confirmed to be an equilibrium phase with three components. The Cu-Sn-Mg ternary system has two ternary compounds, CuSnMg and Cu,SnMg. In spite of reports [4,5] on the existence and the crystal structures of those two compounds, the c~st~lo~aphic~ data were quite insufficient to identify them. High purity starting materials of Cu, Sn and Mg were weighed out to the equivalent compositions of each ternary compound and were put into carbon crucibles and melted in an argon atmosphere. Polycrystalline specimens were prepared by using a vertical Bridgman furnace. Fine powder was collected by percolation; the average particle size was about 10 pm. The relative scattering intensity of Cu K, X-rays monochromatised with an Ni filter was measured by the ordinary 0 - 20 scanning technique and the integrated intensity of each line was obtained after subtraction of the background intensity. The experimental data on the scattering angle for Bragg diffraction and its integrated intensity for the CuSnMg compound are listed in Table 1. As the Laue symmetry was found to be cubic (m3) from an electron diffraction study [ 11, the indices for all Bragg peaks were easily determined as shown in the table; the measured lattice constant was 0.6224 + 0.0001 nm. As the number of chemical units 2 was deduced to be four, the possible positions of the 12 atoms in the unit cell were determined as follows. According to the International Tables [6], for the present space group of T$-Fz3m, we have 4Cu at a43m, 4Sn at d$3m and 4Mg at cz3m. This set of asymmetric positions was selected from the most rational six sets by comparing the observed integrated intensities with the calculated intensities. The calculated intensities are listed in Table 1 where the temperature factor was taken to be 0.0058 nm2. Figure 1 shows the crystal structure of the CuSnMg ternary compound; this is a CaFa-type structure and is similar to that of Mg,Sn. Experimental data for Co characteristic X-rays were reported by Kripiakevich et al. [4] but were inaccurate as shown in Table 1. These workers did
312 TABLE 1 Summary of crystal structure analysis for CuSnMg ternary compound Present work
I
T;-Fi3m
2f3 (“1
d (nm)
Zohs
(W
Ztalc
24.77 28.67 40.98 48.46 50.79 59.35 65.28 67.18 74.63 80.03 88.79 94.09 95.87 108.49 110.38 117.94 124.09 126.29 135.47 143.66
0.3591 0.3111 0.2200 0.1877 0.1796 0.1555 0.1428 0.1392 0.1271 0.1198 0.1101 0.1052 0.1038 0.0949 0.0938 0.0899 0.0872 0.0863 0.0829 0.0811
77.4 16.1 100.0 33.4 4.2 19.3 24.6 6.0 28.2 14.1 7.0 9.8 3.2 5.8 2.3 3.4 5.8 1.8 24.2 13.6
(111) (200) (220)
81.0 19.7 100.0 34.1 4.8 14.3 12.1 5.5 25.3 8.1 7.4 8.0 2.4 3.2 1.5 3.3 6.5 1.5 21.9 13.0
(311) (222) (400) (331) (420) (422) (511)(333) (440) (531) (600)(442) (533) (622) (444) (711)(551) (640) (642) (731)(553)
67 3 7 4 3 3 6 4 5 5 2 4 2 -
-
Fig. 1. Crystal structure of the CuSnMg ternary compound.
not succeed in determining the correct cry&9 st~ctu~. They assumed two possible space groups, Oi-Fm3m and T~-F~3rn. For the former case, two species, Mg and Cu atoms, could substitute for each other. The calculated intensities obtained from these two crystal structures were found to be inconsistent with the present experimental data.
313 TABLE 2 Summary of crystal structure analysis for Cu,$inMg ternary compound Present work
Zobs
T;-F;3m
20 (9
d(nm)
21.84 25.26 36.05 42.55 44.55 56.94 58.5% 64.7% 62.29 76.4% 80.65 87.50 91.69 93.01 109.8% 114.2% 122.16 136.26 142.36
0.4066 0.3523 0.2489 0.2123 0.2032 0.1616 0.1574 0.143% 0.1356 0.1244 0.1190 0.1114 0.1073 0.1062 0.0941 0.0917 0.0884 0.0830 0.0814
Zobs 8.9
5.3 19.9 100.0 19.1 3.0 3.1 7.5 19.6 10.9 2.4 2.5 8.0 5.9 7.8 13.9 2.6 4.2 24.1
VW
(111) (200) (220) (311) (222) (331) (420) (422) (511)(333) (440) (531) (620) (533) (622) (642) (731)(553) (800) (%22)(660) (751)(555)
ZC2llC 9.0
7.6 17.4 51.0 19.4 1.8 2.9 5.0 15.1 11.8 1.3 2.3 5.7 6.9 3.6 14.7 3.6 3.6 20.3
[51 10 10 25 100 45 15 20 40 85 80 20 30 60 65 65 95 50 5 100
A summ~ of the structure analysis on the ~~Sn~g compound is listed m-Table 2. The crystallographical data are as follows: the space group is 7’,2--F43m; the lattice constant is 0.7042 it 0.0001 nm (2 = 4); possible positions of the 24 atoms are 16Cu at e3m (3~= 3/8), 4Sn at a43m and 4Mg at d43m, which are selected from 24 possible sets of asymmetric positions. The assigned indices and the calculated intensities are listed in Table 2, where the temperature factor was 0.0040 nm2_ The experimental data for Cu K, collected by Gladyshevskij et al. [ 51 are also listed. The crystal structure deduced from the present analysis was essentially the same as their result. Its structure is the Laves phase derived from the CusMg structure.
The authors wish to thank Mr. Ryoji Itho and Seizo Takamuku for their technical assistance. 1 2 3 4
K. Osamura, S. Takamuku and Y. Murakami, ‘2. Metallkd., 69 (1976) 467. D. L. Phillips and P. A. Ainsworth, Metallurgiya, 23 (1969) 804. P. A. A&worth and C. 3. Thwaites, Inst. Met. Monogr. Rap. Ser., 34 (1970) 260. P. I. Kripiakevich, E. I. Gladyshevskij and E. E. Herkashin, Dokl. Akad. Nauk SSSR, 75 (1950) 205. 5 E. I. Gladyshevskij, P. I. Kripiakevich and M. J. Tesliuk, Dokl. Akad. Nauk SSSR, 85 (1952) 81. 6 N. F. M. Henry and K. Lonsdaie (eds.), International Tables for X-Ray Crystallography, Vol. 1, Kynoch Press, Birmingham, 1969.
311
Letter
Crystal structures KOZO OS~URA Department (Received
of CuSnMg and Cu,SnMg ternary and YOTARO
compounds
MURAKAMI
of Metallurgy, Kyoto University, 606 Kyoto (Japan)
March 20,1978)
Cu-Sn-Mg ternary alloys have recently been reported by some authors [l - 31 to show precipitation hardening, in which the heterogeneous precipitates on the grain boundary and the homogeneous precipitates in the matrix were confirmed to be an equilibrium phase with three components. The Cu-Sn-Mg ternary system has two ternary compounds, CuSnMg and Cu,SnMg. In spite of reports [4,5] on the existence and the crystal structures of those two compounds, the c~st~lo~aphic~ data were quite insufficient to identify them. High purity starting materials of Cu, Sn and Mg were weighed out to the equivalent compositions of each ternary compound and were put into carbon crucibles and melted in an argon atmosphere. Polycrystalline specimens were prepared by using a vertical Bridgman furnace. Fine powder was collected by percolation; the average particle size was about 10 pm. The relative scattering intensity of Cu K, X-rays monochromatised with an Ni filter was measured by the ordinary 0 - 20 scanning technique and the integrated intensity of each line was obtained after subtraction of the background intensity. The experimental data on the scattering angle for Bragg diffraction and its integrated intensity for the CuSnMg compound are listed in Table 1. As the Laue symmetry was found to be cubic (m3) from an electron diffraction study [ 11, the indices for all Bragg peaks were easily determined as shown in the table; the measured lattice constant was 0.6224 + 0.0001 nm. As the number of chemical units 2 was deduced to be four, the possible positions of the 12 atoms in the unit cell were determined as follows. According to the International Tables [6], for the present space group of T$-Fz3m, we have 4Cu at a43m, 4Sn at d$3m and 4Mg at cz3m. This set of asymmetric positions was selected from the most rational six sets by comparing the observed integrated intensities with the calculated intensities. The calculated intensities are listed in Table 1 where the temperature factor was taken to be 0.0058 nm2. Figure 1 shows the crystal structure of the CuSnMg ternary compound; this is a CaFa-type structure and is similar to that of Mg,Sn. Experimental data for Co characteristic X-rays were reported by Kripiakevich et al. [4] but were inaccurate as shown in Table 1. These workers did
312 TABLE 1 Summary of crystal structure analysis for CuSnMg ternary compound Present work
I
T;-Fi3m
2f3 (“1
d (nm)
Zohs
(W
Ztalc
24.77 28.67 40.98 48.46 50.79 59.35 65.28 67.18 74.63 80.03 88.79 94.09 95.87 108.49 110.38 117.94 124.09 126.29 135.47 143.66
0.3591 0.3111 0.2200 0.1877 0.1796 0.1555 0.1428 0.1392 0.1271 0.1198 0.1101 0.1052 0.1038 0.0949 0.0938 0.0899 0.0872 0.0863 0.0829 0.0811
77.4 16.1 100.0 33.4 4.2 19.3 24.6 6.0 28.2 14.1 7.0 9.8 3.2 5.8 2.3 3.4 5.8 1.8 24.2 13.6
(111) (200) (220)
81.0 19.7 100.0 34.1 4.8 14.3 12.1 5.5 25.3 8.1 7.4 8.0 2.4 3.2 1.5 3.3 6.5 1.5 21.9 13.0
(311) (222) (400) (331) (420) (422) (511)(333) (440) (531) (600)(442) (533) (622) (444) (711)(551) (640) (642) (731)(553)
67 3 7 4 3 3 6 4 5 5 2 4 2 -
-
Fig. 1. Crystal structure of the CuSnMg ternary compound.
not succeed in determining the correct cry&9 st~ctu~. They assumed two possible space groups, Oi-Fm3m and T~-F~3rn. For the former case, two species, Mg and Cu atoms, could substitute for each other. The calculated intensities obtained from these two crystal structures were found to be inconsistent with the present experimental data.
313 TABLE 2 Summary of crystal structure analysis for Cu,$inMg ternary compound Present work
Zobs
T;-F;3m
20 (9
d(nm)
21.84 25.26 36.05 42.55 44.55 56.94 58.5% 64.7% 62.29 76.4% 80.65 87.50 91.69 93.01 109.8% 114.2% 122.16 136.26 142.36
0.4066 0.3523 0.2489 0.2123 0.2032 0.1616 0.1574 0.143% 0.1356 0.1244 0.1190 0.1114 0.1073 0.1062 0.0941 0.0917 0.0884 0.0830 0.0814
Zobs 8.9
5.3 19.9 100.0 19.1 3.0 3.1 7.5 19.6 10.9 2.4 2.5 8.0 5.9 7.8 13.9 2.6 4.2 24.1
VW
(111) (200) (220) (311) (222) (331) (420) (422) (511)(333) (440) (531) (620) (533) (622) (642) (731)(553) (800) (%22)(660) (751)(555)
ZC2llC 9.0
7.6 17.4 51.0 19.4 1.8 2.9 5.0 15.1 11.8 1.3 2.3 5.7 6.9 3.6 14.7 3.6 3.6 20.3
[51 10 10 25 100 45 15 20 40 85 80 20 30 60 65 65 95 50 5 100
A summ~ of the structure analysis on the ~~Sn~g compound is listed m-Table 2. The crystallographical data are as follows: the space group is 7’,2--F43m; the lattice constant is 0.7042 it 0.0001 nm (2 = 4); possible positions of the 24 atoms are 16Cu at e3m (3~= 3/8), 4Sn at a43m and 4Mg at d43m, which are selected from 24 possible sets of asymmetric positions. The assigned indices and the calculated intensities are listed in Table 2, where the temperature factor was 0.0040 nm2_ The experimental data for Cu K, collected by Gladyshevskij et al. [ 51 are also listed. The crystal structure deduced from the present analysis was essentially the same as their result. Its structure is the Laves phase derived from the CusMg structure.
The authors wish to thank Mr. Ryoji Itho and Seizo Takamuku for their technical assistance. 1 2 3 4
K. Osamura, S. Takamuku and Y. Murakami, ‘2. Metallkd., 69 (1976) 467. D. L. Phillips and P. A. Ainsworth, Metallurgiya, 23 (1969) 804. P. A. A&worth and C. 3. Thwaites, Inst. Met. Monogr. Rap. Ser., 34 (1970) 260. P. I. Kripiakevich, E. I. Gladyshevskij and E. E. Herkashin, Dokl. Akad. Nauk SSSR, 75 (1950) 205. 5 E. I. Gladyshevskij, P. I. Kripiakevich and M. J. Tesliuk, Dokl. Akad. Nauk SSSR, 85 (1952) 81. 6 N. F. M. Henry and K. Lonsdaie (eds.), International Tables for X-Ray Crystallography, Vol. 1, Kynoch Press, Birmingham, 1969.