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The hot deformation behaviours of Ti-6Al-4V-0.1Ru alloy were investigated by isothermal hot compression tests in the temperature range of 1023-1423 K and strain rate range of 0.01-10 s -1 . The β transus was determined to be 1198 K by continuous heating method. The values of deformation activation energy Q at the strain of 0.3 were calculated to be 630.01 kJ/mol in dual-phase field and 331.75 kJ/mol in β-phase field. Moreover, the processing maps at the strain of 0.2, 0.4, 0.6 and 0.8 were developed based on dynamic materials model (DMM). To deeply understand the microstructure evolution mechanism during hot deformation processes and to verify the processing maps, the microstructures at different deformation conditions were observed. The stable microstructures (i.e. globularization, dynamic recovery (DRV) and β dynamic recrystallization (β-DRX)) and instable microstructures (i.e. lamellae kinking and flow localization) were obtained. To make it useful in the design of industrial hot working schedules for this material, a microstructural mechanism map was constructed on the basis of processing maps and microstructure observation.

The hot workability of the ultra-high strength steel BR1500HS has been investigated by processing maps. A series of hot deformation tensile tests were carried out on a Gleeble-3500 thermal simulator in the deformation temperature range of 773–1,223 K and strain rate range of 0.01–10 s–1. The obtained flow stress curves reveal that the peak stress increases with the rising of strain rate and decreases with the rising of temperature. Based on dynamic materials model (DMM), the processing maps at the strains of 0.05, 0.10 and 0.15 were developed, and the optimum hot working conditions were recommended as the temperature range of 1,200–1,223 K and the strain rate range of 0.01–0.1 s–1, where the peak power dissipation efficiency is about 37 % revealing the occurrence of typical dynamic recrystallization (DRX). The main instability defects are deformation twinning and micro-crack occurring mainly at the temperature range of 773–873 K with the strain rate higher than 1 s–1. In order to deeply understand the microstructure mechanisms, the Zener–Hollomon parameter is solved, and then the self-diffusion activation energy is compared with the apparent activation energy Q at different deformation temperatures and strain rates.

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