Face-centered tetragonal titanium hydrides in fine-grained commercial pure (grade 2) titanium

• We observed fct titanium hydrides in severely deformed and annealed FG Ti.
• This γ-fct titanium hydride has a c/a ratio of 1.08.
• The γ-fct hydride has inherent orientation relationships with the FG hcp Ti matrix.
• The fct hydride plates were found to be very scarce in this Ti.
• Length of hydride plate cannot be larger than grain size of the hcp matrix.

Face-centered tetragonal (fct) titanium hydride was observed by transmission electron microscopy in commercially pure (CP, grade 2) fine-grained (FG) titanium produced by severe plastic deformation (SPD) and annealing. This γ-fct titanium hydride has a c/a   ratio of 1.08. It was found that the γ-fct hydride possesses inherent orientation relationships with the FG hexagonal close-packed (hcp) α-Ti matrix, namely (110)γ∥(101¯0)α, [001]γ∥[0001]α, [1¯14]γ∥[1¯21¯6]α and [1¯12]γ∥[12¯13¯]α. The fct titanium hydride plates within hcp matrix have the thickness of 10–150 nm and length of 50 nm–3 μm while the matrix grains have the size of 50 nm to 3 μm. The fct titanium hydride was found to be very scarce in this Ti and the relationship between the length of γ-fct hydride and grain size of the hcp matrix has also been discussed.

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