Synopsis

Doing a Crack Job on Aluminum

Physics 5, s118
Atomic simulations of aluminum show how charge transfer from surface impurities can accelerate the growth of a crack tip.
R. J. Zamora et al., Phys. Rev. B (2012)

Engineers and materials scientists have long known that environmental factors can affect the fragility of manufactured components. Sometimes this is useful, as when a glassmaker applies a drop of water to a scribe mark to facilitate a clean break. More often, the chemical environment leads to reduced durability, as when aluminum under cyclic loading experiences a higher failure rate if the humidity increases. These effects are typically studied with a top-down approach: assemble lots of data on the way different materials respond to an environmental stress to arrive at a general mechanism. But a microscopic bottom-up approach is possible now with advanced computing tools, as Rick Zamora and colleagues at Cornell University, New York, report in Physical Review B.

The authors used the NASA Pleiades supercomputer to simulate the behavior of a crack in aluminum at an atomic level under different environmental conditions. These detailed multiscale calculations were run for three cases: a crack tip with no impurities, a crack tip with a single hydrogen atom, and a crack tip with a single oxygen atom. Zamora et al. ramped up the load on the simulated sample until a dislocation was created.

Results from these calculations predict that the hydrogen and oxygen impurities strenghen the aluminum bonds at the surface by means of charge transfer, inhibiting plasticity at the crack and raising the likelihood of brittle fracture. With this ab initio calculation, the Cornell team shows that a bottom-up approach can be a valuable tool for understanding embrittlement due to environmental causes. – David Voss


Subject Areas

Materials SciencePhysical Chemistry

Related Articles

A Chiral Crystal’s Orbital Texture
Materials Science

A Chiral Crystal’s Orbital Texture

X-ray experiments reveal that a semimetal exhibits “orbital texture”—an exotic electronic structure resulting in spin-dependent electron transport. Read More »

Electron–Hole System Harbors Rich Phases
Materials Science

Electron–Hole System Harbors Rich Phases

Researchers predict that several exotic states of matter can exist in semiconductor structures hosting electrons in one layer and holes in another. Read More »

Electrochemists Wanted for Vocational Degrees
Physical Chemistry

Electrochemists Wanted for Vocational Degrees

Paul Kempler runs a master’s program at the University of Oregon that provides hands-on electrochemistry training for those wanting to enter the field without them having to take a five-year-long PhD. Read More »

More Articles