Fig. 1 a Photographs of the as-cast rod and the cylindrical sample, b hydrogenation and solution aging, c various hydrogen contents obtained during hydrogenation

Fig. 2 XRD patterns of the as-cast microstructure and the hydrogenated microstructures

Fig. 3 Optical micrographs of the as-cast microstructure a and the hydrogenated microstructure (0.984 wt% H) b

Fig. 4 XRD patterns of the aged microstructures

Fig. 5 SEM micrographs of the aged microstructures. a 0.259 wt% H, b 0.430 wt% H, c 0.569 wt% H, d 0.820 wt% H, e 0.984 wt% H

Fig. 6 a TEM micrograph of the aged microstructure (with 0.984 wt% H), b SADP of a coarse primary phase, c SADP of a fine primary phase

Fig. 7 a Content of βH at the end of hydrogenation and aging, b size of primary α phase at the end of aging

Fig. 8 Effect of hydrogen content on the size of primary α phase. Curve 1 shows effect of undercooling on α size, curve 2 shows effect of eutectoid decomposition, and curve 3 shows sum of the two effects. A pseudo-Ti-H diagram is presented to show undercooling and formation of δ. Formation of primary α at three different hydrogen contents (low, medium and high) is presented. Rp0.2 is yield strength, Rm is ultimate strength, A is unit extension, and Z is reduction of area

Fig. 9 Tensile properties of the as-cast sample and the sample processed with THT