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This paper is concerned with the fabrication and evaluation of composites of pure aluminum reinforced with sapphire wool type whiskers. The composites were prepared by initially coating the as-grown whiskers with a duplex coating of nickel and titanium utilizing a sputtering technique, orienting the coated whisker bundle, and infiltrating the bundle with liquid aluminum. Evaluation of the composites was primarily conducted by elevated temperature tension tests at 500 C in order to separate alloy strengthening effects from fiber strengthening. Composite strengths as high as 54,900 psi at 500 C were obtained, which represents about a hundredfold strength increase over pure aluminum. On a strength-to-density ratio, this value is comparable to titanium alloys at similar temperatures. In spite of these high strengths, the full “theoretical” strength as computed by the rule of mixtures was not achieved. Allowing about 10 per cent whisker strength decrease at 500 C, and utilizing reasonable values for the whisker strength, the upper limit of the experimenta l composite strengths was approximately 40 per cent of the “theoretical” strength. The reasons for this deviation are attributed to structural factors such as poor fiber orientation and insufficient fiber length at 500 C because of low matrix shear strength. These factors may be expected to improve with further development work.
metal matrix, composite materials, composite fabrication, alumina, evaluation, physical properties
Mehan, R. L.
Metallurgist, General Electric Co., King of Prussia, Pa.