Workability and microstructure evolution of Ti-47Al-2Cr-1Nb alloy during isothermal deformation

The isothermal compression behavior and microstructure evolution of ingot metallurgy processed samples of Ti-47Al-2Cr-1Nb (at.%) were studied. The true stress-strain curves and processing window of Ti-47Al-2Cr-1Nb were set up through isothermal compression test. A grain refining method of TiAl based alloy was submitted, which included two-step deformation with a short intermediate heat-treatment between the double deformation. The refining mechanism was characterized as breaking and bending of the lamellae, dynamic recrystallization, and static globularization. The results showed that canned billets had more homogeneous microstructures, and higher strain (height induction) could be reached without cracks than ones without being canned. The break-down operation of the canned ingot was performed by the isothermal forging processing mentioned above. Thus, a uniform and refined billet microstructure was obtained for the final component forging operation. The deformation of two model disks were accomplished by subsequent single-step isothermal forging at temperature of 1100-1150 °C using a closed compression die. Three kinds of microstructures (fully lamellar, near lamellar and duplex) with small size were obtained respectively in the as-forged component through post heat-treatment conducted in different phase field.