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Properties of many materials are influenced strongly by small compositional changes that occur at interfaces such as phase and grain boundaries. Knowledge of the elements involved and whether they are segregated or present in a second phase provides a better understanding of the failure mechanism. In many instances of grain boundary failures, the chemistry provides the most comprehensive and useful information. Examples of such studies discussed here include temper embrittlement and other forms of impurity-induced low temperature embrittlement, weld-metal embrittlement, grain boundary corrosion, and intergranular stress corrosion cracking. Failures at phase boundaries and other more macroscopic interfaces such as encountered in fiber/metal matrix composites, interparticle interfaces in powder metallurgy materials and bonded (thermal compression, solder, or diffusion bonded) interfaces also can be understood by close examination of chemistry of these interfaces.
In many of these examples, the zone of segregation at boundaries is very small, only a few angstroms, the same as the boundary width. The interface chemistry has been studied successfully in a scanning Auger microprobe by Auger electron spectroscopic analysis of grain boundary fracture surfaces obtained inside the vacuum system.
fractography, Auger electrons, spectroscopy, embrittlement, fractures, (materials) grain boundaries, corrosion, stress corrosion, weld metal, composite material, hydrogen embrittlement
Assistant director, Analytical Laboratory, Physical Electronics Industries, Inc., Eden Prairie, Minn.