Evaluation of the Influence of the Nucleation Undercooling on Columnar Grain Growth During Al-Cu Alloy Directional Solidification

An analytical model was developed to evaluate the influence of initial grain density over the chill on the texture formation during directional solidification. The model is based on competitive grain growth mechanism. The Al - 3wt%Cu alloy was used in a directional solidification process to verify the accuracy of the model. Two different nucleation densities over the chill plate were produced using various water flow rates in the cooling system. Cooling curves of the alloy during solidification were monitored using thermal analysis. Optical microscopy and image analysis were used to analyze the grain structure of the solidified samples. Also, the cellular automaton finite element (CAFE) method was used for numerical calculations to comprise the results of the present analytical model with numerical simulation. The results showed that the increment of the nucleation undercooling would ease the formation of well-oriented <001> texture in the starter block. Experimental and numerical data were in good agreement with the results of analytical model.