Hydrogen-induced hardening of Ti-6Al-4V alloy in B phase field
Isothermal compression tests were conducted to investigate the hot deformation behaviour of a Ti-6A1-4V alloy with different hydrogen contents at tempertures of 1050-1100 degrees celcius, and strain rates of 0.005, 0.01, 0.1 and 1s-1 respectively. The miscrostructural evolution was investigated via optical microscope, x-ray diffraction and transmission electron microscope the mechanism of hydrogen-induced hardening was discussed. The experimental results showed that hydrogen could be retained in Ti-6A1-4V alloy even though the temperature was increased to 1100 degrees in the air hydride with a face-centred cubic crystal strucutre existed in the deformed matrix and the size of hydride reduced when the deformation temperature was increased from 1050 to 1100 degrees. Hydrogen induce the increased flow stress and work hardening rate of Ti-6A1-4V alloy when deformed in B phase field. Hydrogen had a positive effect on the development of twinning in Ti-6A1-4V alloy. Based on the analysis of both hot deformation behaviour and microstructural evolution, it is indicated that the hydrogen induced twinning plays a key role in the enhancement of work hardening of Ti-6A1-4V alloy in B phase field.
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