Microheterogeneity and crystallization conditions of Fe-Mn melts

We have obtained original experimental data on the viscosity and supercooling of Fe-Mn melts with a Mn content of 5, 7, 10, 12 and 15 wt% for optimization of high-manganese Hadfield steel (11.5-15.0 wt% Mn) smelting technology. The experimental data on the viscosity is analyzed based on the hypothesis about the microheterogeneity of metal melts. The optimal manganese content in Hadfield steel of 12 wt% is found. It is shown that the heating Hadfield liquid steel before crystallization up to 1500 degrees C destroys microheterogeneity. The effect of the destruction of Hadfield liquid steel microheterogeneity on crystallization conditions has been studied. The change in crystallization conditions is assessed by changes in microstructure morphology, crystal structure and nanomechanical properties. The optical microscopy, energy-dispersive X-ray spectroscopy and electron backscattered diffraction are used for the study of morphology, elemental composition and crystal structure of solid solution dendrites. The destruction of microheterogeneity leads to manganese dendritic segregation during solidification. The nanoindentation is used to measure hardness and the Young modulus of manganese-rich (20-30 wt% Mn) segregation layer and dendrite volume. The obtained values are used for calculation of the adhesion of segregation layer K-int = 4.8 MPa.m(0.5) and the fracture energy of an inhomogeneous dendrite G(c) = 95 J.m(-2).