Ti-6Al-4V alloys consisting of α-Ti grains and intergranular β-Ti islands were nitrided at 850°C for 1 to 12 h under a nitrogen pressure of 1 Pa. With increasing nitriding time, the Ti-N compound layer became thicker, and the α-Ti diffusion zone containing dissolved nitrogen became wider. In the Ti-N compound layer, the initially formed Ti2N became TiN as the nitriding progressed. The nitride layers were oxidized to rutile-TiO2 after oxidation at 700°C for 10 h in air.

Plastic deformation and strain-induced martensite (SIM, α′) transformation in metastable austenitic AISI 304 stainless steel were investigated through room temperature tensile tests at strain rates ranging from 2 × 10⁻⁶ to 2 × 10⁻²/s. The amount of SIM was measured on the fractured tensile specimens using a feritscope and magnetic force microscope. Elongation to fracture, tensile strength, hardness, and the amount of SIM increased with decreasing the strain rate. The strain-rate dependence of RT tensile properties was observed to be related to the amount of SIM. Specifically, SIM formed during tensile tests was beneficial in increasing the elongation to fracture, hardness, and tensile strength. Hydrogen suppressed the SIM formation, leading to hydrogen softening and localized brittle fracture.

Hydrogen embrittlement behavior with respect to strain-induced martensite (SIM, α′) and the dislocation structure in 316L stainless steel were investigated using tensile testing at strain rates of 2 × 10⁻⁶ to 2 × 10⁻² s⁻¹ at room temperature. The deformed specimens with and without hydrogen were examined using MFM, neutron diffraction, TEM, and a Feritscope. The results showed that ductility, tensile stress, and hardness increased with decreasing strain rate and an increasing amount of SIM. Hydrogen caused SIM to be distributed locally in a α′/γ laminated structure. The H-free sample had a larger quantity of SIM than the H-charged sample at the same plastic strain. Hydrogen changed the dislocation structure from only cellular to a mixed structure comprising both cellular and planar dislocations. H-charged 316L SS had a diffuse reflection, which implied that short-range ordering formed during tensile testing. It was concluded that hydrogen induced planar dislocation and suppressed SIM formation, leading to cleavage fracture and softening.