Effect of graphene nanoflakes on the hydrogen embrittlement behavior of laser powder bed fusion formed titanium matrix composites

Abstract

The Ti-6Al-4 V alloy produced by laser powder bed fusion (LPBF) is one of the most typical titanium (Ti) alloys, combining the characteristics of α-Ti and β-Ti. Due to its low density, high strength, good toughness, and biocompatibility, it is widely used in fields such as aerospace, high-speed trains, and medical implants. However, its specific microstructure is sensitive to hydrogen absorption and embrittlement, which limits its broader application. This paper investigates the effects of doped graphene nanoflakes (GNFs) on the microstructure and hydrogen embrittlement (HE) resistance of LPBF-formed titanium matrix composites (TMCs) through microscopic characterization and slow strain rate tensile testing with electrochemical hydrogen pre-charging. The results indicate that the presence of hydrogen atoms adversely affects both the strength and plasticity of the composites with varying graphene content, with increased sensitivity to HE as the graphene content rises. The strength loss rates for composites with 0 wt%, 0.1 wt%, and 0.2 wt% GNFs are 7.29 %, 4.84 %, and 19.23 %, respectively, while the plasticity loss rates are 51.70 %, 59.91 %, and 60.57 %. The fracture mode is primarily a mixed ductile–brittle fracture, with the crack initiation and propagation mechanisms transitioning from transgranular fracture to intergranular fracture. These findings provide a theoretical basis and technical support for the engineering application of LPBF-formed TMCs in hydrogen-rich service environments.