Hot deformation behavior and microstructural evolution of ultrafine-grained TZM alloy

This research investigated the hot deformation behavior and microstructure evolution of ultrafine-grained TZM alloy over a temperature range of 1200–1350 °C and strain rates from 0.001 to 1 s⁻¹. A strain-compensated Arrhenius constitutive model was developed and hot working maps were generated. Microstructural analysis revealed that at low temperatures and high strain rates, dynamic recrystallization (DRX) was insufficient, leading to a higher dislocation density and strong texture. As the temperature increased and the strain rate decreased, grain deformation was predominantly controlled by continuous dynamic recrystallization (CDRX). The proportion of recrystallized grains increased, as indicated by a rise in high-angle grain boundaries (HAGBs) and a reduction in dislocation density. Furthermore, the results showed that 〈100〉//CD and 〈111〉//CD were the primary slip directions. Elevated temperatures and reduced strain rates promoted the preferential growth of recrystallized grains along <100>//CD, enhancing texture strength. Based on the experimental findings, a schematic model of the microstructural evolution of ultrafine-grained TZM alloy during high-temperature deformation was proposed.