Prediction of Primary Dendrite Arm Spacing with Solidification Velocity and Temperature Gradient during Directional Solidification in CMSX-4 Superalloy

Directional solidification experiments were carried out to estimate the effect of solidification velocity and temperature gradient on primary dendrite arm spacing (PDAS) in the Ni-based superalloy, CMSX-4 alloy. The specimens were solidified at velocities of 1, 5, 25, 50 and 100 mm/s under given temperature gradients of 12.5, 18, 23 K/mm. The models for predicting PDAS with solidification conditions had the form of λ ∝ V−1/4G−1/2, but the experimental results exhibited a discrepancy with the exponents of −1/4 and −1/2 in V and G, respectively. Therefore, a phenomenological formula based on the experimental results was proposed to predict PDAS, and it was found that the predicted PDAS under the experimental conditions was in good agreement with the experimental results. Key words: directional solidification, dendrite arm spacing, temperature gradient, Ni base superalloy