Transformation of non-metallic inclusions “eutectics” in steels under laser action
Melting and crystallization of heterophase non-metallic inclusions ―eutectics‖ was investigated. Mechanism of melting of the eutectic inclusions and inclusion-matrix boundaries under contact laser melting with steel matrix in the conditions of abnormal mass transfer connecting with formation of zones with high dislocation density and also with electron and electro-magnetic interaction between inclusion and steel matrix was proposed. That allows to create the possibilities for the influence on the inclusion-matrix boundaries and also on the chemical and phase composition of surface layer of non-metallic inclusions. Peculiarities of structure of non-metallic inclusions after speed crystallization were investigated. It was shown that under laser action the initial composite colonial structure of inclusions transits into abnormal eutectic structure. Also it was shown that under laser action the initial structure of inclusion-steel matrix boundaries transits into unstable equilibrium high-energy condition that cause development of the dissipation processes connecting with aspiration of system inclusion-matrix to the state with minimum of the free energy. In the result of the system eutectic inclusion-matrix transits to the state of unstable equilibrium which determines structure and properties of laser-quenched interphase boundary. Processes of melting, fusion and dissolution of non-metallic inclusions ―eutectics‖ and also of the melting of steel matrix play the great role in transformation of interphase inclusion-matrix boundaries under laser action.