Effects of thermomechanical processing on texture formation in titanium aluminides

To study the texture development in advanced materials, cast titanium aluminides of different composition (alloy A: Ti-47Al-4(Cr, Nb, W Si, B) and alloy B: Ti-45Al-10Nb) have been deformed by forging and extrusion at different temperatures corresponding to different fractions of the alpha- (A3) or alpha(2)- (D0(19)) and gamma- (L1(0)) phase. The textures of the gamma-phase have been measured by neutron diffraction. Forging alloy B at 1100degreesC in the alpha(2) + gamma phase field leads to a <032] + <110] double fibre texture. Deforming the alloys at temperatures between 1250degreesC and 1380degreesC, with increasing temperature the gamma-fraction decreases and becomes zero above the alpha-transus temperature. Correspondingly, the fibre textures obtained by extrusion through a round die change from [001] + <111> via <111> to <011] + <110] + <112]. Extrusion through a rectangular die of alloy B at 1295degreesC, when it mainly consists of alpha-phase, yields a dominant {111}<112> component. The type and strength of texture are discussed with regard to starting texture, phase mixture, deformation mode, slip and twinning activity, dynamic recrystallization, grain boundary sliding and phase transformations.