Composite Strengthening.
Abstract
Annealed aluminum/silicon carbide (Al/SiC) composites exhibit a relatively high density of dislocations frequently decorated with fine precipitates in the Al matrix that contributes to the unexpected strength of these composite materials. The large difference (10:1) in the coefficient of thermal expansion (CTE) between Al and SiC results in sufficient stress to generate dislocations at the Al/SiC interface during cooling. In this in situ investegation, using a High Voltage Electron Microscope (HVEM) equipped with a double tilt heating stage, composite samples were observed during heating to 800 K and cooling to ambient temperatures to determine the density of dislocations generated at the Al/SiC interface during cooling. Two types of bulk annealed composites were examined: one with SiC of discontinuous whisker morphology and one of platelet morphology. In addition, control samples with O V% SiC were examined. Both types of composites showed the generation of dislocations at the Al/SiC interface resulting in densities > 1,000,000,000/sq. cm. One sample viewed end-on to the whiskers showed only a rearrangement of dislocations, whereas the same material when sectioned so that the lengths of whiskers were in the plane of the foil, showed the generation of dislocations at the ends of the whiskers on cooling. The control samples did not show the generation of dislocations on cooling except at a few large precipitate particles.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 1984
- Accession Number
- ADA161615
Entities
People
- R. J. Arsenault
Organizations
- University of Maryland