Analysis of structural changes and phase transformations in Sikhote-Alin IIAB iron meteorite under various origin shock deformation

摘要

A comparative analysis of structural and phase transformations in the Sikhote-Alin meteorite with different shock prehistory has been done: shards from the impact crater, conditionally unstressed individual fragments and samples after model experiments on spherically converging shock waves loading. This meteorite belongs to the class of coarse octahedrites, and Fe-Ni-Co alloy with P, S and N impurities. Techniques of optical and scanning electron microscopy with energy dispersive X-ray spectrometry (EDS) and electron backscatter diffraction (EBSD) analysis units have been used for provided information on temperature and deformation changes in extraterrestrial matter in case of impact of space and terrestrial conditions, as well as in case of shock-wave loading. The formation of specific structural elements of deformation in shards of meteoritical substance from an impact crater was observed: curved Neumann lines, fibrous structure, regions of localized flow in the alpha-phase kamacite Fe (Ni, Co) and traces of brittle localized destruction of rod-shaped phosphides (Fe,Ni)3P. Analysis of the behavior of an extraterrestrial substance during model explosive loading gave an opportunity to match microstructural changes occurring in the meteorite substance and factors accompanying shock-wave action. Localized flows and traces of ductile fracture of thin roaldite plates (FeNi)4N have been observed. Intensive generation of new twins in the near-surface zone of samples due to localization of deformation and increase of local pressure up to 20 GPa was detected. Systematization of structural and phase changes in an inhomogeneous substance of Sikhote-Alin meteorite depending on the intensity of the shock wave effects has been suggested.