Oxygen nanoclustering evades inverse Hall-Petch softening

Area of Science:

• Materials Science
• Metallurgy
• Nanotechnology

Background:

• Grain refinement enhances metal strength but faces limitations at nanoscale (<10-20 nm) due to grain boundary instability and restricted dislocation activity.
• This inverse Hall-Petch effect necessitates new strategies for strengthening ultra-fine grained materials.

Purpose of the Study:

• To present a novel strategy for simultaneously achieving high strength and plasticity in nanograined metals.
• To investigate the role of oxygen (O)-rich clusters in enhancing grain boundary stability and deformation mechanisms in nanostructured alloys.

Main Methods:

• Investigated a (CoCrNi)87O13 (at.%) alloy with 3 nm grain size.
• Utilized micropillar compression tests to evaluate mechanical properties.
• Analyzed the influence of oxygen clusters on grain boundary stability and dislocation behavior.

Main Results:

• Oxygen-rich clusters at grain boundaries significantly enhanced stability in the 3 nm nanograined CoCrNi alloy.
• Oxygen clusters in grain interiors promoted dislocation accumulation and multiplication, facilitating strain hardening.
• The (CoCrNi)87O13 alloy demonstrated a yield strength of ~3.6 GPa and over 50% uniform plastic strain, even in the inverse Hall-Petch regime.

Conclusions:

• Oxygen clusters offer a universal design strategy to overcome the inverse Hall-Petch effect in nanograined metals.
• This approach enables the simultaneous achievement of high strength and large ductility, crucial for advanced material applications.