Crystallographic orientation dependence of hydride precipitation in commercial pure titanium

Ti and its alloys have a variety of applications in aerospace industry and medical implants. The formation of hydride has been used in biomedical areas and can significantly influence the mechanical performance of materials. In this work, we investigate the orientation dependence of hydride precipitation in commercially pure titanium via interrupted in-situ electron backscatter diffraction (EBSD) measurements. The results reveal that hydrides during hydrogen charging at room temperature exhibit two types of orientation relationships with α-titanium, i.e., {0001}_α//{11¯1}_δ <12¯10>_α//<110>_δ with interface plane {101¯3}_α//{11¯0}_δ (B-type), and {0001}_α//{001}_δ <12¯10>_α//<110>_δ with interface plane {101¯0}_α//{11¯0}_δ (P-type). Significant orientation dependence of hydride precipitation is observed, especially when {101¯3}, {101¯0}, {0001} or {112¯0} planes of the parent grains are parallel to the diffusion surface. The displacement gradient tensor based accommodation shows that the orientation dependence is attributed to the strain relaxation of hydride transition. Three types of hydride platelets are characterized: parallel hydride platelets (Type I), crossed hydride platelets (Type II) and clustered hydride platelets (Type III). The multiple morphologies of hydride platelets resulting from the hydride variant selection and interaction are dependent on the crystal orientation of the matrix.