DEFORMATION AND MICROSTRUCTURE DEVELOPMENT DURING HOT-PACK ROLLING OFA NEAR-GAMMA TITANIUM ALUMINIDE ALLOY

Deformation behavior and microstructure development during hot pack ro lling of the near-gamma titanium aluminide alloy Ti-45.5Al-2Cr-2Nb (at omic percent) were established. Deformation behavior was investigated through rolling at various nominal furnace temperatures and parallel m odeling studies using a finite difference approach to predict temperat ure transients during workpiece transfer from the furnace and during t he rolling operation itself. Agreement between measured rolling pressu res and predictions based on a rule-of-mixtures (ROM) average of the f low stresses of the pack components (at the predicted temperatures and strain rates within the roll gap) was excellent. As-rolled microstruc tures were interpreted in terms of the Ti-xAl-2Cr-2Nb pseudobinary pha se diagram, predicted temperature transients during rolling, and the s tatic (no deformation) phase-transformation behavior of the program ma terial. These results demonstrated the strong influence of furnace pre heat temperature on microstructure development, as well as the tendenc y for temperature transients due to radiation heat losses and roll chi lling to suppress phase transformations.