THE CREEP AND FRACTURE BEHAVIOR OF Al-Al3Ni EUTECTIC WHISKER COMPOSITES.
UNITED AIRCRAFT CORP EAST HARTFORD CONN RESEARCH LABS
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A series of Al3Ni eutectic creep specimens was fabricated from ingots solidified at 11.0 cmhr and these specimens were creep tested at a single set of conditions to plastic strains in the first, second, and third stages of creep, and to rupture. The tests were then interrupted and the specimens were sectioned and examined by transmission electron microscopy. It was found that due to the small plastic strains encountered in the first and second stages epsilon sub p or 0.3 of creep, relatively little substructure buildup was encountered in these specimens. In specimens tested to rupture dense dislocation cells keyed on the whiskers were found. As a result, a time dependent fracture mechanism was identified which was quite different from normal tensile fracture, and this mechanism was related to the substructure buildup. Solidification experiments conducted at approximately 3.5 cmhr resulted in the formation of a dual-orientation microstructure in which portions of the whiskers were misaligned from the nominal growth direction. This structure was found to be extremely detrimental to creep behavior. The modes by which premature specimen failure occurred were identified and the fracture mechanisms determined. Microstructural characterization studies were conducted on ingots solidified over a range of rates from 3.5 to 35 cmhr. Author
- Laminates and Composite Materials
- Properties of Metals and Alloys