ADSORPTION-INDUCED BRITTLE FRACTURE IN LIQUID METAL ENVIRONMENTS
MARTIN MARIETTA CORP BALTIMORE MD RESEARCH INST FOR ADVANCED STUDIES
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Solid metals can be caused to behave in a brittle manner by exposure to a variety of physical or chemical environments. Perhaps the most dramatic examples of such effects, however, result from exposure to surface active liquid metals. Specimens pre-stressed above some critical value fail virtually instantly on being wetted by an appropriate liquid metal, and brittle crack propagation rates of order 100 cm per sec. have been recorded in otherwise ductile metals under such environmental conditions. Such effects are presently considered to result from adsorption-induced reductions in the cohesive strength of atomic bonds at regions of stress concentration in the solid metal, e.g. at the tips of cracks or in the vicinity of piled up groups of dislocations. This paper describes the results of a number of recent investigations on this type of liquid-metal embrittlement, and discusses the prerequisites and possible mechanisms for its occurrence. Also discussed are the effects of such variables as chemical composition of the solid and liquid metal phases, temperature, prestrain, rate of loading, etc., on severity of embrittlement, and such topics as the possible correlation between severity of embrittlement and electronegativity, the use of inert carrier liquid metals, possible means of inhibiting liquid-metal embrittlement, and criteria for brittle failure.
- Metallurgy and Metallography