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Embrittlement of brass by ammoniacal solutions and mercury Birley, Stuart Samuel

Abstract

The influence of a liquid metal and a stress corrosion environment on the mechanical properties of α and β brasses was investigated under continuous tensile loading conditions: strain rate and grain size (α brass only) were systematic variables. Increasing strain rate or decreasing grain size was found to increase the ductility and fracture stress of the polycrystalline material in either environment. Single crystal studies revealed (1) that grain boundaries are not essential for embrittlement by either media and (2) that the surface films induced by the environment are mechanically very weak. The fractured surfaces of a brass were examined (1) for topographical features using both direct and indirect replica electron microscopy and (2) for evidence of thin films using a low angle electron diffraction technique. Crack path in both environments was invariably intergranular, and details of fractured surfaces were similar. Thin films were detected on the fractured surfaces, and the compositions determined. In general, both environments conferred the same general embrittling effects. It is possible to account for the current observations by a common cracking mechanism: the development of such a model based on the slip step displacement of a passive surface film is discussed.

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