EFFECTS OF HEAT-TREATMENT ON MICROSTRUCTURE AND TEXTURE IN TI-24AT-PERCENT-AL-11 AT-PERCENT-NB

Hot cross-rolled sheets of Ti-24at.% -11at.%Nb are subject to heat treatments in the α2 + β phase field and in the β phase field. Changes in microstructure are monitored by metallography while crystallographic texture is evaluated by pole figure analysis. Annealing in the α2 + β regime produces equiaxed α2 grains and intergranular β with little modification to the starting texture. Annealing in the β regime results in a Widmanstätten structure whose lamellar spacing depends on the cooling rate. A much sharper texture in the α2 phase is observed. The sharpness of the β phase texture correlated with the sharpness of the α2 texture. Hardness measurements indicate that the highest strength occurs in the fine Widmanstätten structure where rapid cooling from the β regime produces the greatest amount of microstructural refinement. © 1990.