The results of the comparative study of the microstructure, crystal structure, and mechanical properties in microvolumes of the Fe–25 wt % Mn–2 wt % С alloy crystallized from melt in different structural states—homogeneous and heterogeneous—were presented. The study was performed by means of scanning electron microscopy Energy Dispersive X-Ray Spectroscopy (EDX), electron backscatter diffraction (EBSD), and nanoindentation. The destruction of microheterogeneity in the Fe–Mn–C melts was established to lead to an increase in the dendrite parameter, the size of crystallites, and the fraction of low-angle boundaries under cooling and further crystallization. The surface of austenite dendrites was revealed to contain manganese-rich liquation layers, which had a thickness 〈L〉 = 60 µm and a manganese content of 35–40% and led to deformation nonuniformity of an ingot. The adhesion strength of the liquation layer to the body of an austenite dendrite was estimated as Kint = 9.6–13.1 MPa m0.5 and could not be a reason for the destruction of an ingot.