Microstructural Evolution of Primary Dendrite Trunks in Directionally Solidified, Hypoeutectic, Aluminum-Silicon Alloys

摘要

The primary dendrite arms in directionally solidified materials, e.g., turbine blades, serve as continuous fibers that extend the casting length and contribute to strength and ductility. Previously, it has been shown that the primary dendrite trunk diameter (d), like other microstructural constituents, exhibits predictable behavior as a function of the solidification processing parameters of growth velocity (V), temperature gradient (G), and composition (C_0). Additionally, it responds more quickly to changes in these parameters than, for example, the primary (λ_1) arm spacing and is thus a better indicator of the local solidification conditions. The work presented here will follow and discuss evolution of the trunk diameter as a function of distance through the mushy zone in directionally solidified Al-Si alloys with the intent of providing some insight regarding micro-structural development.