Microstructure of Ti–V–Mn BCC alloys before and after hydrogen absorption–desorption

Microstructure of Ti–V–Mn BCC alloys before and after hydrogen absorption–desorption was investigated using transmission electron microscopy. Strain contrast with spacing of 5–50 nm was observed along (1 0 1) planes of the BCC phase in both the as-cast alloys and the alloys after hydrogenation–dehydrogenation. Twin boundaries and stacking faults with spacing of 5–100 nm were introduced into the Ti–V–Mn BCC alloys after hydrogen absorption–desorption. These were parallel to the (1 0 1) of BCC alloys and (1 1¯ 1) of remained FCC hydrides. The twin boundaries and stacking faults were formed due to accommodation of the shear stress during hydrogenation accompanied by large anisotropic expansion along the c-axis direction in the Ti–V–Mn BCC alloys.

Research highlights▶ Nano-size lattice strain was observed in the as-cast Ti–V–Mn BCC alloys. ▶ This lattice strain was also visible after hydrogen absorption–desorption cycles. ▶ Twin boundaries and stacking faults were introduced after the cycle. ▶ Planar defects were formed due to accommodation of shear stress during hydrogenation.