Influence of Extrusion Temperature on Microstructure of Ti-47A1-2Cr-2Nb-0. 15B

Influences of extrusion temperature on the deformed and subsequently thermomechanically treated lamellar (TMTL) microstructures of Ti47A1-2Cr-2Nb-0. 15B alloy as observed on the transverse section were investigated. Canned ingots were axisymmetrically-extruded through a flat die to an extrusion ratio of 8 1. The extruded rods on the transverse section consisted of fine duplex microstructure at the edge and fully lamellar (FL) at the center. However, the FL microstructure at the center changed with increasing extrusion temperature: the rods contained remnant lamellae and partially recrystallized FL grains after extrusion at 1250 degrees C and 1280 degrees C, and consisted of completely recrystallized grains after extrusion at 1300 degrees C, with the size and volume fraction of the recrystallized FL grains increasing with the increase of extrusion temperature. The heterogeneity of deformed and TMTL microstructures is believed to be caused by nonuniform deformation and temperature distribution due to deformation heating and die chilling.