Quantitative Characterization of Beta Fleck Segregation in a Ti-17 Alloy Ingot Produced by Vacuum Arc Remelting Without Electromagnetic Stirring

Beta flecks (β-flecks), known as segregation defects, commonly occur in some α + β and metastable β titanium alloys with a high content of β-stabilizing elements such as Cr and Fe, seriously impacting the mechanical properties of the final product. In this work, an experimental Ti-17 alloy ingot was produced by vacuum arc remelting (VAR) processes without electromagnetic stirring. β-flecks were identified throughout the entire ingot. To quantitatively characterize the segregation extent and morphological complexity of β-flecks, three parameters, including quantity (Q), segregation ratio (R_β) and fractal dimension (D_PA), were introduced. The results show that β-flecks with two shapes exist in three regions: irregular β-flecks formed in a spherical shape region (Region A) in the lower part and a heart shape region (Region B) in the upper part of the equiaxed zone, while channel-like β-flecks formed in a V shape region (Region C) in the hot top zone. β-flecks formed in Region A show a higher degree of segregation extent (higher Q and R_β) and morphological complexity (higher D_PA), compared to those in Region B. These findings suggest that solidification conditions, particularly temperature gradient (G) and solidification rate (R), play crucial roles in the formation of β-flecks during the VAR process. By quantifying permeability in different sections of the equiaxed zone, liquid flow and its impact on the formation of β-flecks during solidification processes are discussed.