Effect of continuous cooling on solid phase transformations in TiAl-based alloy during Jominy end-quench test

摘要

The effect of continuous cooling on solid phase transformations in Ti-47Al-STa (at.%) alloy was studied using Jominy end-quench test. The microstructure of as-quenched Jominy samples continuously changes from γm(TjAI) + α(Ti-based solid solution) through nearly massive γm to lamellar γ(TiAl) + α2(Ti_3Al) and γm with increasing distance from the water cooled surface. The cooling curves calculated numerically by finite element method (FEM) using available material properties deviate from the experimental data. The application of inverse numerical correlation (INC) method reconciles the calculated cooling curves and cooling rates with the experimentally measured ones. The highest volume fraction of the massive γm is achieved at local average cooling rates ranging from 10 to 20°Cs~(-1). While the water and oil cooling from the solid solution annealing temperature leads to numerous short as well as long cracks, the fan and air cooling are identified to be suitable for the grain refinement of cast components through formation of high volume fraction of massive γm grains.