Nanotechnology

Organic chemistry

Nanoscopic scale

Hydrogen

Analytical Chemistry (journal)

Engineering

Transmission electron microscopy

Composite material

Focused ion beam

Atom probe

Chemistry

Metallurgy

Materials science

Corrosion

Scanning electron microscope

Hydride

Layer (electronics)

Alloy

Titanium

Metal

Titanium hydride

Chemical engineering

Chromatography

Ion milling machine

Titanium alloy

Hydrogen embrittlement

Nature Communications

Hydrogen pick-up leading to hydride formation is often observed in commercially pure Ti (CP-Ti) and Ti-based alloys prepared for microscopic observation by conventional methods, such as electro-polishing and room temperature focused ion beam (FIB) milling. Here, we demonstrate that cryogenic FIB milling can effectively prevent undesired hydrogen pick-up. Specimens of CP-Ti and a Ti dual-phase alloy (Ti-6Al-2Sn-4Zr-6Mo, Ti6246, in wt.%) were prepared using a xenon-plasma FIB microscope equipped with a cryogenic stage reaching −135 °C. Transmission electron microscopy (TEM), selected area electron diffraction, and scanning TEM indicated no hydride formation in cryo-milled CP-Ti lamellae. Atom probe tomography further demonstrated that cryo-FIB significantly reduces hydrogen levels within the Ti6246 matrix compared with conventional methods. Supported by molecular dynamics simulations, we show that significantly lowering the thermal activation for H diffusion inhibits undesired environmental hydrogen pick-up during preparation and prevents pre-charged hydrogen from diffusing out of the sample, allowing for hydrogen embrittlement mechanisms of Ti-based alloys to be investigated at the nanoscale.

Ti and its alloys as examples of cryogenic focused ion beam milling of environmentally-sensitive materials