Control of microstructure for Co-Cr-Mo fibers fabricated by unidirectional solidification

Co-Cr-Mo alloy fibers of 2 mm in diameter were fabricated from the melt at 1, 2, and 5 mm/min growth rates by unidirectional solidification using an alloy-micro-pulling-down (A-µ-PD) method to control the microstructure. All elements, Co, Cr, and Mo, were distributed in stripes elongated along the growth direction due to constitutional undercooling. Both Co-Cr-Mo fibers fabricated at 2 and 5 mm/min growth rates were composed of the γ phase with a face-centered cubic structure (fcc-γ phase) and ε-phase with a hexagonal close-packed structure (hcp-ε phase), and the ratio of the fcc-γ phase in the fiber fabricated at 5 mm/min growth rate was higher than that in the fiber fabricated at 2 mm/min. The results suggest that a faster growth rate increases the ratio of the fcc-γ phase in the Co-Cr-Mo fiber fabricated by unidirectional solidification.