In-situ hydrogen embrittlement evaluation of as-built and heat treated laser powder bed fused Ti-6Al-4V versus conventionally cold rolled Ti-6Al-4V AITranslate

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DOI：https://doi.org/10.1016/j.addma.2023.103768

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The hydrogen embrittlement (HE) is investigated for the titanium alloyTi-6Al-4V, processed by different manufacturing methods. The mechanical characteristics of conventionally cold rolled, as-built laser powder bed fused (L-PBF) and heat treated L-PBF Ti-6Al-4V are compared under in-situ electrochemical hydrogen charging at room temperature. The microstructure determines the susceptibility to HE, which is examined by a combination of in-situ constant extension rate tensile tests, X-ray tomography, X-ray diffraction, hydrogen melt extraction, scanning electron microscopy, and electron backscatter diffraction. The presence of the β phase facilitates an increased hydrogen uptake capacity, resulting in an enhanced HE-susceptibility. In-situ hydrogen assisted failure of a duplex α-β microstructure in conventionally cold rolled Ti-6Al-4V occurs via a strain rate dependent mechanism, i.e. hydrogen enhanced localised plasticity (HELP) at fast strain rates and a combination of HELP and stress induced hydride formation (SIHF) at slow strain rates. Meanwhile, the martensitic α’ microstructure of as-built L-PBF Ti-6Al-4V shows clear evidence of prevalent hydrogen degradation via SIHF after slow straining. However, hydrogen significantly deteriorates the mechanical behaviour in L-PBF material due to a fatal synergetic interaction with porosity related stress fields, dominating failure characteristics after hydrogenation. The same effect applies for the inherent porosities in heat treated L-PBF Ti-6Al-4V with a fine α-β microstructure. Therefore, knowledge on these microstructural interactions with hydrogen will allow the development of better HE resistant Ti-6Al-4V. Graphical Download : Download high-res image (311KB) Download : Download full-size image