The influence of environment on the formation of fluting microstructures during fracture of zircaloy

Fluting microstructures are commonly-occurring features on Zircaloy fractures produced under stress-corrosion cracking (SCC) and liquid (or solid) metal embrittlement (LME) conditions and they are generally closely associated with areas of cleavage cracking. Although it is widely believed that flutings are a consequence of localised plastic deformation near the cleavage cracks and that the aggressive chemical agents do not contribute directly to fluting formation there is little clear experimental evidence to support that view. Consequently the small programme of tests, described here, was performed in order to ascertain whether flutings can be generated in Zircaloy during exposure to stress in the absence of a SCC or LME agent. The implications of the results are discussed in terms of the currently proposed mechanisms for fluting formation in particular, and crack propagation generally, in Zircaloy SCC fracture. (orig.)