Microstructure evolution and mechanical properties of Fe-Cr-B alloy during directional solidification

This study investigated microstructure formation as a function of solidification velocity during the directional solidification (DS) of Fe-Cr-B alloy. The experiments showed that the size, volume fraction and orientation of borides were effectively controlled. With the increase of solidification velocity, boride morphology is modified and the martensite transforms to the cellular structure at 2 μm/s and the equiaxed structure at 500 μm/s. The corresponding mechanical properties were compared with those of the ingot samples. The toughness and strength of the DS samples were approximately 155% and 70% higher, respectively, than those of the ingot samples. Field emission scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and analysis of the morphology and volume fraction of borides revealed the underlying mechanisms behind these enhancements. This study provides insight into microstructure control and contributes to the understanding of the mechanical properties of high-performance Fe-Cr-B alloys.