Constrained Dendritic Growth and Solute Concentration Effects in Rapidly Solidified Co-Cr Alloys

Abstract

Growth temperature and dendrite tip radius equations were employed in this work in order to predict the experimental conditions under which a Co-Cr alloy was produced having a single γ-phase microstructure free from interdendritic segregation. The outcome of these predictions indicated that in Co alloys containing 20 to 25 wt pct Cr, single γ-phase dendritic microstructures are achieved independently of the implemented solidification growth velocities. Moreover, these alloys are found to be essentially free from interdendritic segregation. Co alloys containing 30 to 35 wt pct Cr exhibit both the γ-phase and the eutectic constituent when solidification rates (V) are below 0.1 and 0.5 mm/s, respectively. Alternatively, the eutectic constituent is suppressed when the solidification growth velocities exceed these values. In particular, it is found that a single-phase microstructure can be achieved when the solidification growth rates exceed the transition velocity between constitutional supercooling and the absolute stability conditions.