Investigation of hydrogen-deformation interactions in β-21S titanium alloy using thermal desorption spectroscopy

The effect of heat treatment and HCF performance on hydrogen trapping mechanism in Timetal LCB alloy

“…It is assumed that hydrogen interacts with the dilatational stress field around a dislocation forming a Cottrell-type atmosphere, which will result in a drag force, making the dislocation movement more difficult and changing the slip character. Birnbaum and Sofronis specifically demonstrate that apparent hydrogen-induced hardening can result from slip localization [7,13]. …”

“…The apparent activation energy for hydrogen evolution can be estimated using Kissinger's method from the shift in peak temperatures with the increase in the applied heating rate [6,7]. Applying Kissinger's analysis, the activation energy for hydrogen release may be calculated from the slope of ln(ϕ/T 2 p ) versus 1/T p , where ϕ is the heating rate and T p is the peak temperature value.…”

“…However, in many technological applications, this alloy can be exposed to environments which might act as sources of hydrogen, and ␤-titanium alloys are known to be susceptible to hydrogen embrittlement. In previous studies on bcc ␤-Ti alloys it has been observed that hydrogen in solid solution in the ␤ lattice, well below the expected terminal solubility limit for the formation of a hydride, can have a significant effect on the ductile-to-brittle transition leading to a change in the fracture mode from ductile, micro-void coalescence to brittle cleavage [4][5][6][7]. In contrast to most steels showing a loss in ductility, in the ␤-Ti alloy no hydrides were associated with the fracture process, and the mechanism responsible for the sharp ductile-to-brittle transition and the decrease in the fracture load with increasing hydrogen concentration, was concluded to be the decohesion mechanism of hydrogen embrittlement [6,7].…”

“…In previous studies on bcc ␤-Ti alloys it has been observed that hydrogen in solid solution in the ␤ lattice, well below the expected terminal solubility limit for the formation of a hydride, can have a significant effect on the ductile-to-brittle transition leading to a change in the fracture mode from ductile, micro-void coalescence to brittle cleavage [4][5][6][7]. In contrast to most steels showing a loss in ductility, in the ␤-Ti alloy no hydrides were associated with the fracture process, and the mechanism responsible for the sharp ductile-to-brittle transition and the decrease in the fracture load with increasing hydrogen concentration, was concluded to be the decohesion mechanism of hydrogen embrittlement [6,7]. Therefore, a comprehensive knowledge of hydrogen-trapping interactions is necessary to make any decision on whether a trap site, or particular trapped hydrogen content, is detrimental to safe service conditions of this alloy in automotive and other applications in the industry.…”

Influence of hydrogen content on hot deformation behavior and microstructural evolution of Ti600 alloy

“…Becauseˇphase, with bcc (body-centered cubic) structure, can be easily deformed at high temperature, the use of hydrogen as a temporary alloying element is always added into titanium alloys during hot deformation processing. In the 1970s, scholars in former Soviet Union began to investigate the influence of hydrogen on thermo-plasticity of titanium alloys, and it had been found that the addition of hydrogen could reduce the flow stress and enhance the plasticity of˛, near-˛, +ˇand intermetallic-base alloys [13][14][15][16]. The work of Kolachov [17] showed that the flow stress after hydrogenation was only 1/3 of that without hydrogen after 0.6% (mass fraction) hydrogen was added into the Ti 3 Al based CT5 alloy, moreover, there was no crack occurred even though 80% deformation was carried out at 900 • C. After 0.2% (mass fraction) hydrogen was charged in the Ti-14Al-19Nb-3V-2Mo alloy, the deformation temperature was lowered by about 50 • C and the strain rate was increased by one order of magnitude [18].…”