Thermal expansion of the directionally solidified Al--CuAl/sub 2/ eutectic
Alloys of Al-CuAl/sub 2/ eutectic composition were prepared with high purity materials (99.999%) and directionally solidified horizontally in a rectangular ceramic boat at 0.96, 4.0, 8.3, 17.5, and 82.0 ..mu..m/sec through a temperature gradient of 45/sup 0/C/cm. These ingots were examined macroscopically and the best single grain regions were selected for further measurements. From micrographs taken of the top, side and cross section of the ingot, it was found that the interlamellar spacings were 7.5, 3.5, 2.6, 1.8 and 1.4 ..mu..m respectively, and from the measured lamellar orientation relationships specimens were machined with axes aligned in the principal lamellae coordinate directions. Transmission Laue photographs taken using Ni filtered Cu K..cap alpha.. radiation verified that the texture is consistent with the crystallographic relationships (121)/sub theta/ vertical bar vertical bar (111)/sub Al/; <12anti 3>/sub theta/ vertical bar vertical bar <1anti 21>/sub Al/. Thermal expansion was measured by standard dilatometry (Cu standard) using a set point program cycling between room temperature and 500/sup 0/C. It was found that the thermal expansion of the directionally solidified Al-CuAl/sub 2/ eutectic decreases with increasing interlamellar spacing, is greatest in the growth direction (approximately <1anti 21>/sub Al/, in the plane of the lamellae) least in the transverse direction (approximately <10anti 1>/sub Al/, in the plane of the lamellae), and intermediate in the second transverse direction (approximately <111>/sub Al/ normal to the lamellae). These results confirm that the CuAl/sub 2/ phase is anisotropic with respect to thermal expansion, but the interlamellar spacing dependence of thermal expansion is not predicted by any known theory of composite materials.
- Research Organization:
- California Univ., Berkeley (USA). Lawrence Berkeley Lab.
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 6534199
- Report Number(s):
- LBL-7682
- Country of Publication:
- United States
- Language:
- English
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