Hostname: page-component-586b7cd67f-r5fsc Total loading time: 0 Render date: 2024-11-25T19:45:37.741Z Has data issue: false hasContentIssue false
  • English
  • Français

Off-Axis Mechanical Properties of A Cellular Al-Al 3Ni Directionally Solidified Eutectic

Published online by Cambridge University Press:  15 February 2011

Dennis W. Hetzner ,
Ben F. Oliver  and
William T. Becker
Ben F. Oliver
Affiliation:
University of Tennessee, Knoxville, TN37916
William T. Becker
Affiliation:
University of Tennessee, Knoxville, TN37916
Get access

Abstract

Ingots having a cross-sectional area of 1.27 cm × 10.8 cm were directionally solidified for testing off-axis tensile properties. To avoid macroscopic banding due to inductive melting and thermal convection, growth rates of 2.2 cm/min were required. The resulting solidification structures were cellular.

The macroscopic tensile behavior of the eutectic alloy was similar to that observed for mechanically formed fiberreinforced composite materials; in particular, three distinct modes of fracture occurred. In Region I, where the angle(ϕ) between the growth direction and the tensile axis was small, the tensile strength of the composite was inversely proportional to cos2 ϕ. In Region II (20° ≤ ϕ ≤ 55°) and Region III (60° ≤ ϕ ≤ 90°), the tensile strength of the composite was inversely proportional to sin ϕ, cosϕ, and sin 2ϕ, respectively.

For all regions, failure was initiated by the fracture of large Al3Ni intercellular blades. In Region I, fracture was by a combination of tensile overload on a plane perpendicular to the tensile axis or shear on a plane inclined to the tensile axis at approximately 45°. In Region II, failure was by shear in a plane containing the growth direction and in a direction parallel to the fibers. For Region III, failure was by plane strain constraint with shear perpendicular to the longitudinal axis of the fibers.

The fracture of large intercellular Al3Ni blades can be explained by the variation of S13 about the tensile axis, and the corresponding intercellular tensile strains which result. In Region II, metallographic examination of tensile specimens shows a Poisson's ratio effect to be contributing to the strength of the composite; occasionally shear between adjacent cells is observed. By using the yield strengths of specimens having fibers oriented parallel to and perpendicular to the tensile axis, an approximate yield surface can be constructed. This yield surface accurately predicts the transition in failure mode from Region II to Region III.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 12: Symposium L – In Situ Composites IV , 1981 , 329
Copyright
Copyright © Materials Research Society 1982

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

1. Lemkey, F. D., Hertzberg, R. W., and Ford, J. A., “The Microstructure, Crystallography, and Mechanical Behavior of Unidirectionally Solidified Al-Al 3Ni Eutectic,” TAIME, 233, 1965, p. 334.Google Scholar
2. Farag, M. M. and Flemings, M. C., “Structure and Strength of Al, Cu-Al3 Ni Directionally Solidified Composites,” Met Trans, 6A, 1975, p. 100.Google Scholar
3. Hertzberg, R. W., Lenkey, F. D., and Ford, J. A., “Mechanical Behavior of Lamellar (Al - CuAl2) and Whisker Type (Al - Al3Ni) Unidirectionally - Solidified Eutectic Alloys,” TAIME, 233, 1965, p. 342.Google Scholar
4. Farag, M. M., and Abd El Latif, M. H., “An Analysis of the Mechanical Behavior of Al - Al3 Ni Composites”, Met. Trans., 6A, 1975, p. 1353.Google Scholar
5. Barclay, R. S., Kerr, H. W., and Niessen, P., “Off Eutectic Composition Solidification and Properties of Al-Ni and Al - Co Alloys,” J. Mat. Sco., 6, 1971, p. 1168.Google Scholar
6. Lawson, W. H. S. and Kerr, H. W., “Mechanical Behavior of Rapidly Solidified Al - Al 2Cu and Al - Al3Ni Composites,” Met. Trans., 2, 1971, p. 2853.Google Scholar
7. Stowell, E. Z., and Liu, T. S., “On the Mechanical Behavior of Fiber Reinforced Crystalline Materials,” J. Mech. & Phys. Solids, 9, 1961, p. 242.Google Scholar
8. Dupeux, M., and Durand, F., “Anisotropic Tensile Properties of Lamellar Al - CuAl2 Eutectics,” Met. Trans., 6A, 1975, p. 2143.Google Scholar
9. George, F. D., Ford, J. A., and Salkind, M. J., “The Effect of Fiber Orientation and Morphology on the Tensile Behavior of Al3 Ni Whisker Reinforced Aluminum,” Metal Matrix Composites, ASTM STP 438, Amer. Soc. Testing & Mat., 1968, p. 59.Google Scholar
10. Hetzner, D. W., Oliver, B. F. and Becker, W. T., “Cellular Microstructure of Al-Al3Ni Directionally Solidified Eutectic,” Submitted to Metallography.Google Scholar
11. Grabel, J. V., and Cost, J. R., “Ultrasonic Velocity Measurement of Elastic Constants of Al - Al3 Ni Directionally Solidified Eutectic,” Met. Trans., 3, 1972, p. 1973.Google Scholar
12. Backofen, W. A., Deformation Processing, Addison-Wesley Publishing Co., Reading, MA, 1972.Google Scholar
13. Hill, R., The Mathematical Theory of Plasticity, Oxford University Press, Cambridge, England, 1950.Google Scholar