Abstract
The hot deformation behavior of a novel near-beta titanium alloy Ti-5.5Mo-6V-7Cr-4Al-2Sn-1Fe in (α+β) phase region in the temperature of 605~755℃ and strain rate range of 10-3~10-1/s-1 was investigated on the Gleeble-3800 thermo-mechanical simulator. The results showed that the deformation parameters can have a significant influence on flow softening behavior and the microstructure evolution, as well as dynamic recrystallization is remarkable at temperature 755℃and strain rate 10-3s-1. The flow stress decreases with the increase of temperature and decrease of strain rate. With the rise of temperature and strain rate, the content of α phase gradually decreases. During the thermal deformation process, the α phase content decreases with the increase of the strain rate and the size of α phase decreases with increasing temperature. αGB is short rod or spherical. Andα phase precipitated after short-term aging preferentially nucleated within the grains after aging treatment. Moreover, the thermal-mechanical process does not induce α phase generation compared to general heat treatment.
Highlights
Near-β titanium alloys have been widely used in aviation, medical, petrochemical and other fields owing to its low density, high specific strength, excellent match of strength, ductility and toughness (Qin et al, 2018; Zhang and Chen, 2019)
The following conclusions can be drawn from the present study: (1) Deformation temperature and strain rate can significantly affect the thermal deformation behavior
The flow softening process is affected by dynamic recovery (DRV), DRX and α phase spheroidization
Summary
Near-β titanium alloys have been widely used in aviation, medical, petrochemical and other fields owing to its low density, high specific strength, excellent match of strength, ductility and toughness (Qin et al, 2018; Zhang and Chen, 2019). More studies focus on the phase transition behavior of titanium alloy during hot deformation. It is still necessary to study the microstructure evolution and phase transition behavior in the thermal deformation of near-β titanium alloy. The present study is carried out to clarify the flow behavior and microstructure evolution of Ti-5.5Mo-6V-7Cr-4Al-2Sn-1Fe in (α + β) phase region, which provides supportive information on effect of stress on phase transition by comparing aging and thermal deformation. In order to study the effect of stress on the α phase transition, the heat treatment test without stress was carried out on the Gleeble-3800 thermo-mechanical simulator. The thermal compression test was conducted on Gleeble-3800 thermo-mechanical simulator in the temperature of 605∼755◦C and strain rate range of 10−3∼10−1 s−1. The morphology of α phase was observed by scanning electron microscopy
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