Investigation of crystallization processes Fe-B-C alloys

Objective o f the paper is study of crystallization peculiarities of Fe-B-C system alloys for composition triangle Fe-Fe2B-Fe3C Methods. The investigation was performed for alloy with boron content from 1,8...3% and carbon content of 2 .2 ,5% (wt.), the rest is iron. To ascertain the chemical composition of alloy chemical analysis and X-ray microanalysis was used. Phase composition of alloy was revealed by means of microstructure and X-ray structure analysis. The temperature of phase transformations in alloys was determined by means of thermal analysis. Results. Structure of alloys with boron content of 2,4% (wt.) and carbon content of 2,1% (wt.) after melting and crystallization consists of primary austenite crystals and eutectic y-Fe+Fe3(CB) with sheet-like morphology. As a result of next reheating, melting and crystallization the structure of alloy consists of decomposed austenite dendrites and two different in structure eutectics: sheet-like eutectic y-Fe+Fe3(CB) and core eutectic y-Fe+Fe23(CB)6. Structure of Fe-B-C system alloy with boron content of 2,95 % (wt.) and carbon content of 2,3 %(wt.) consists of primary bright dendrites of Fe3(CB) phase and sheet-like eutectic y-Fe+Fe3(CB). After smelting alloy was preannealed at the temperature of 1170 K for hour. After this alloy was heated up to temperature 30 K above the liquidus and then was cooled with rate of 40 K/min. Microstructure of alloy consists primary borides Fe2B, located inside large edged crystals of Fe23(CB)6 phase and finely-divided eutectic y-Fe+Fe23(CB)6 with core morphology. Scientific novelty. In alloys with boron content from 1 ,8 .3% and carbon content of 2 .2 ,5% (wt.) after melting and crystallization the formation of primary austenite crystals and eutectic y-Fe+Fe3(CB) with sheet-like morphology takes place. The next remelting and crystallization or holding for hour at the temperature 30 K above the liquidus of these alloys leads to formation of austenite and eutectic y-Fe+Fe23(CB)6. Practical implications. The results of the investigation enable to project and effect on the phase composition and phase transformations in alloys of Fe-B-C system.