The competitive growth of dendrite arrays in the directional growth of a thin sample

Abstract:

The high performance blade has been the widely applied to increase the efficiency of the aircraft engine, and its fabrication has been well developed. However, the appearance of misoriented grains always decrease of production yield. Competitive growth of dendrite arrays with different orientation in directional solidification is an important phenomenon for the fabrication of single crystal blade. The question has caught attention for many years. The tip undercooling has been the only criterion for the elimination of unrefereed dendritic grains for a long time and is implanted in commercial software ProCAST to simulate the grain growth. However, the experimental bicrystal growth in directional solidification identified the drawback of the tip undercooling criterion. Quantitative phase field simulations showed more details of the bicrystal competitive growth. The grain boundary evolution has been one of the key indicators for competitive growth. The previous tip undercooling criterion could not predict the grain boundary evolution. The huge phase field simulations reveal the statistic evolution rule of the grain boundary direction. In this paper, we proposed a sheet sample with multiple bycrystals configurations. The microstructures were observed in a stitching picture. The competitive growth and the grain boundary selection of dozens of biocrystals have been summarized within several samples. The statistical results agree with the phase field simulation. However, the CAFE simulation results from the ProCAST can not predict the grain boundary evolution. The method proposed here can be applied to investigate the competitive growth with a high throughput way. The results are helpful to understand the unoriented grains in fabrication of single crystal blade.

Key words:directional;solidification, competitive;growth, grain;boundary direction