CRYSTALLOCHEMICAL INTERACTIONS IN METAL-OXIDE SYSTEM UNDER MICROWAVE ELECTROMAGNETIC IRRADIATION

Crystallochemical interaction was studied in sintered powder mixtures of austenitic stainless Cr18Ni15 steel and alumina after prolonged mic rowave irradiation. It was shown by metallography, electron and X-ray diffraction and electron probe microanalysis that two-years exposure t o electromagnetic radiation gives rise to the change in the phase comp osition and structural state of the material-absorber with the formati on of the 0.7-1.0 mm thick surface layer. In this layer, the metallic constituent (an fee austenite) completely disappears, the amount of al uminum oxide is reduced and traces of Fe and Cr oxides appear. Irradia ted specimens contain, as the base, heterophase mixtures and solid sol utions of spinels (hercynite, chromits, chromoaluminum spinels). The p hase composition of the specimen core does not practically change, bei ng the two-phase mixture of an fee (gamma) Fe and a rhombohedral Al2O3 . Substantial change in the structure and phase composition of the sur face layers causes the reduction in reflectivity by a factor of 1.6.