Microstructure and mechanical properties of high boron iron-based alloy solidified in different moulds

The as-cast microstructures of high boron iron-based alloy samples solidified in investment mould and metal mould all comprises dendritic matrix and interdendritic eutectic boride Fe2B. With increasing cooling rate, the size of dendritic matrix is decreased, and the morphology of Fe2B is changed from fishbone form to mesh form, and the boride is distributed more uniformly, but its chemical composition remains unchanged. After a heat treatment of austenitizing at 1030 degrees C for 1 h, quenching in water and tempering at 200 degrees C for 1 h. the matrixes of samples cast in the two moulds are most1v changed to lath-like martensite, the boride cast in investment mould remains unchanged, otherwise the borides cast in metal mould becomes granulated. The mechanical properties of samples cast in metal mould is better than those of samples cast in investment mould, among which, the hardness is increased by 5.9%, tensile strength 17.5% and impact toughness 60%.