In-situ investigation of grain boundary premelting behavior in low-carbon ferromanganese

High-temperature laser scanning confocal microscopy (HT-LSCM) was employed to directly observe the grain boundary premelting behavior of industrial low-carbon ferromanganese. During heating, the alloy undergoes solid-state microstructure evolution, accompanied by progressive grain boundary broadening, liquid film formation and intergranular liquefaction prior to bulk melting. Comprehensive characterization results demonstrate that carbon segregation induces the formation of low-melting intergranular regions, which triggers the preferential grain boundary premelting during heating. Liquid film coalescence readily occurs in the subsequent solidification process, while a high cooling rate can effectively suppress the growth and coalescence of intergranular liquid films and optimize the microstructure uniformity of the alloy.