Surface-Stress Induced Embrittlement of Metals.
basic_science · Level V
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- Record sourced from PubMed, PMID 34726060.
- Also identified by DOI 10.1021/acs.nanolett.1c02887.
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Abstract
Environment-assisted fracture phenomena in metals are usually associated with surface energy reduction due to an adsorbed film. Here we demonstrate a unique embrittlement effect in Al that is instead mediated by surface stress, induced by an adsorbed organic monolayer. Atomistic simulations show that the adsorbate carbon-chain length <i>l</i><sub>c</sub> controls the surface stress via van der Waals forces, being compressive for <i>l</i><sub>c</sub> < 8 and tensile otherwise. For <i>l</i><sub>c</sub> > 8, we demonstrate experimentally that the nanoscale film causes a ductile-to-brittle transition on the macroscale. Concomitant with this transition is a nearly 85% reduction in deformation forces. Additional simulations reveal that the microscopic mechanism for the embrittlement is via suppression of dislocation emission at incipient crack-tips. In addition to challenging long-held views on environment-assisted fracture, our findings pertaining to surface-stress induced embrittlement suggest profitable utility in manufacturing processes such as machining and comminution.