Solidification microstructure of Ti-43Al alloy by twin-roll strip casting

As a near-net-shape technology, the twin-roll strip casting (TRC) process can be considered to apply to the fabrication of TiAl alloy sheets. However, the control of the grain distribution is very important in strip casting because the mechanical properties of strips are directly determined by the solidification microstructure. A three-dimensional (3D) cellular automation finite-element (CAFE) model based on ProCAST software was established to simulate the solidification microstructure of Ti-43Al alloy. Then, the influence of casting temperature and the maximum nucleation density (nmax) on the solidification microstructure was investigated in detail. The simulation results provide a good explanation and prediction for the solidification microstructure in the molten pool before leaving the kissing point. Experimental and simulated microstructure show the common texture <001> orientation in the columnar grains zone. Finally, the microstructure evolution of the Ti-43Al alloy was analyzed and the solidification phase transformation path during the TSC process was determined, i.e., L → L+β → β → β+α → α+γ+β/B2 phase under a faster cooling rate and L → L+β → β → β+α → γ+lamellar (α2+γ)+β/B2 phase under a slower cooling rate.