Microstructural evolution in silicon alloyed γ-Ti-Al alloys after thermomechanical processing

The microstructures of silicon alloyed gamma-Ti-Al alloys containing silicide particles have been studied after thermomechanical treatments to investigate microstructural evolution. Important parameters including temperature forging strain, and sequence of thermomechanical treatments were systematically studied. Isothermal forging below the eutectoid temperature resulted in inhomogeneous dynamic recrystallisation with fine equiaxed grains in recrystallised areas and residual alpha(2) + gamma lamellae elsewhere. Eutectic silicides play an important role in destruction of the as cast structure by promoting dynamic recrystallisation during deformation and static recrystallisation on subsequent annealing. There is evidence that silicon, in solution, also enhances recrystallisation. The presence of fine silicides produced by precipitation in the solid state restricts fire size of grains produced by both dynamic and static recrystallisation. Silicon also alter's significantly the phase equilibrium between the alpha and gamma phases.