Hydrogenation-induced lattice expansion and its effects on hydrogen diffusion and damage in Ti–6Al–4V

Roughening improves hydrogen embrittlement resistance of Ti-6Al-4V

“…It is also observed that the average proof stress of the two polished specimens was ~100 MPa lower than the uncharged material. The decrease in yield strength is consistent with the literature [10,32,33], as hydride formation typically reduces the yield stress due to the generation of internal stresses from the volume expansion. In the following analyses, we will focus our attention mostly on the difference in the failure strain between the non-polished (S1 and S2) and polished (S3 and S4) specimens.…”

“…The EBSD phase map in Figure 3 indicates that the new dark phase is a hydride phase, which corresponds to a previous work [10]. Kim et al and Chang et al reported that the initial hydride phase in the Ti-6Al-4V alloy is formed at the α/β phase boundary (indicated by yellow arrows in Figure 2(f,h)) and has a face-centered tetragonal crystal structure of stoichiometry close to TiH1.5, as predicted by density functional theory calculation [10,35,36]. By further H-ingress, hydride laths would grow inside the primary α grains, similar to the hydrides that form in α-Ti alloys [31,37].…”

“…Figure 1(c) shows the stress-strain curves of the different specimens after H-charging, and Table 2 summarizes the average properties based on three repeats (error given by standard deviation). Interestingly, the H-charged specimens of S1 and S2 exhibit similar tensile response to the uncharged S1 specimen, with a slight increase in fracture strain instead of the drastic reduction normally expected after Hcharging [10,31]. In contrast, both polished specimens show premature fracture, with fracture strain reduced to 2.6% and 1.8% for the S3 and S4 specimens, respectively.…”

“…In contrast, prior to the 1950s, titanium was widely considered to be insusceptible to HE in aqueous environments due to its protective oxide film [2]. However, from the 1960s onward evidence accumulated that hydrogen leads to a range of degradation phenomena in titanium, which continues to cause engineering concerns for industry [2,[6][7][8][9][10]. The majority of research in the hydrogen embrittlement (HE) of titanium focuses on the behavior of hydrogen once it is absorbed into the metal [2,8,11].…”

Recent Advances in the Design of Novel β‐Titanium Alloys Using Integrated Theory, Computer Simulation, and Advanced Characterization

“…As an example, nucleation and growth of the hydride during the hydrogen charging of the α/β Ti–6Al–4V alloy has been investigated using the in situ SEM/EBSD characterization technique. [ 127,128 ] The starting microstructure consists of globular (equiaxed) α grains dispersed in a transformed β matrix (i.e., fine‐scale α laths separated by β ribs). The α phase exhibits both equiaxed and lamellae morphologies.…”