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

Abstract

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 (α + β) phase field region and subsequent isothermal annealing treatments at 1150 °C for different holding times. During forging and the following cooling process a fine grained microstructure is formed consisting of lamellar α2/γ colonies and elongated grains of the βo 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 α2(α) phase exhibits a 〈11-20〉 fiber, the βo(β) phase has a strong and sharp fiber and the γ phase shows a and a weaker fiber. After additional annealing at 1150 °C for 8 h, the textures are almost unchanged in contrast to the microstructure.