Effect of growth rate on directionally solidified microstructure of Cu-7.9%Co peritectic alloy

Directionally solidified micro structures of Cu-7.9%Co peritectic alloy have bee investigated at the growth rate ranging from 1 μm/s to 100 μm/s. The results show that the morphology of α-Co primary phase changes from a columnar dendrite to an equiaxed dendrite and its volume fraction decreases with increasing of growth rate. Simultaneously, the interface morphology of β-Cu peritectic phase becomes unstable from planar to dendritic interface. The theoretical analysis results indicate that α-Co phase can grow ahead of β-Cu phase as the growth rate ranges from 0.55 μm/s to 5000 μm/s, which is in agreement with the experimental results. In addition, when the growth rate is more than 5000 μm/s, β-Cu phase can grow as the primary phase and directly solidifies from the liquid metal without peritectic reaction.