Mechanical properties and flow stress constitutive relationship of Ti-6Al-4V alloy with equiaxed microstructure at cryogenic temperatures

This paper investigates the uniaxial tensile mechanical properties and flow behavior of Ti-6Al-4V alloys with equiaxed microstructure at cryogenic temperatures ranging from 77 K to 298 K and strain rates from 10-4/s to 10-2/s. Scanning electron microscopy is utilized to analyze the fracture morphology, aiming to reveal the fracture behavior at various temperatures. The applicability of the Zener-Hollomon parameter and the Johnson-Cook model in describing the flow stress of Ti-6Al-4V at cryogenic temperatures is analyzed. Moreover, a constitutive relationship modeling method based on the variational recurrent networks is proposed. Mechanical test results show a significant increase in the strength of equiaxed Ti-6Al-4V alloy under cryogenic conditions while the plastic deformation process is shortened. However, the fracture analysis indicates that even at 77 K, the fracture process is still dominated by ductile fracture, and brittle fracture does not occur within the range of 77 K to 298 K. The fitting results validate the performance of the Zener-Hollomon parameter and the Johnson-Cook model in describing the deformation flow stress of Ti-6Al-4V alloy at cryogenic temperatures. The results also indicate that the proposed constitutive relationship modeling method based on the variational recurrent network performs better, making it a potential method for widespread applications. (c) 2024 Production and hosting by Elsevier Ltd. on behalf of Chinese Society of Aeronautics and Astronautics. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).