Microstructure and Texture Evolution in an Intermetallic b-Stabilized TiAl Alloy During Forging and Subsequent Isothermal Annealing

Microstructure and texture formation were investigated in an intermetallic Ti-43.4Al-4.2Nb-1.1Mo-0.1B (in at.%) alloy after near conventional forging in the (+) phase field region and subsequent isothermal annealing treatments at 1150 degrees C for different holding times. During forging and the following cooling process a fine grained microstructure is formed consisting of lamellar (2)/ colonies and elongated grains of the (o) phase situated at the colony boundaries. The isothermal annealing treatment leads to a significant change of the forged microstructure. After hot-forging, all phases show typical fiber textures as it is expected for uniaxial deformation. In the as-forged state the (2)() phase exhibits a 11-20 fiber, the (o)() phase has a strong and sharp 001 fiber and the phase shows a 110 and a weaker 101 fiber. After additional annealing at 1150 degrees C for 8h, the textures are almost unchanged in contrast to the microstructure.