Hot deformation behaviour and microstructure evolution of TiAl-based alloy reinforced with carbide particles

The hot deformation behaviour and microstructure evolution of TiAl-based alloy with nominal composition TT 43Al-8Nb-3.6C-0.7Mo (at.%) reinforced with carbide particles were studied. The compression tests were carried out in the temperature range from 900 to 1000 degrees C and strain rates from 0.0001 to 0.01 s(-1) up to a true strain of 0.5. The microstructure of the compression specimens was characterised using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron backscatter diffraction (EBSD). The work hardening stage of the flow curves results from an increment of the dislocation density and deformation twins. The work softening of the composite results from the dynamic recovery (DRV), dynamic recrystallization (DRX) and fragmentation of some coarse Ti2AlC particles. The size of recrystallised grains increases with decreasing Zener-Hollomon parameter. The non-uniform distribution of local strains in the deformed specimens and deformation temperature affect the orientation and fragmentation of coarse Ti2AlC particles. A constitutive model predicting hot deformation behaviour of the studied alloy is proposed and its validity is evaluated and discussed.