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Open Access Publications from the University of California

Scholarly Works (2 results)

  • Thesis
  • Peer Reviewed
UC Berkeley Electronic Theses and Dissertations (2022)

α-Ti and α-Ti alloys are of technological interest as high specific strength, corrosion resistant, nonmagnetic, and bio-compatible materials. However, they are costly to process and require strict control of the presence of interstitial impurities that cause significant strength gains, but also loss of ductility. This work uses atomistic simulations to examine the properties of dislocation cores, i.e. the regions in a material surrounding a dislocation that has been deformed beyond it’s ideal strength in α-Ti and α-Ti alloys. Particular attention is paid to the interactions between these dislocations and solute atoms. It is shown that dislocation core structure affects the interaction with interstitial oxygen, and that solute atoms may be used to influence the dislocation core structure of screw dislocations through the so-called Cottrell atmosphere.

    Cover page: ⟨a⟩-type Screw Dislocation Core Structure and Solute Interaction in α-Ti
    • Article
    • Peer Reviewed
    UC Berkeley Previously Published Works (2020)
    One of the most potent examples of interstitial solute strengthening in metal alloys is the extreme sensitivity of titanium to small amounts of oxygen. Unfortunately, these small amounts of oxygen also lead to a markedly decreased ductility, which in turn drives the increased cost to purify titanium to avoid this oxygen poisoning effect. Here, we report a systematic study on the oxygen sensitivity of titanium that provides a clear mechanistic view of how oxygen impurities affect the mechanical properties of titanium. The increased slip planarity of Ti-O alloys is caused by an interstitial shuffling mechanism, which is sensitive to temperature, strain rate, and oxygen content and leads to the subsequent alteration of deformation twinning behavior. The insights from our experimental and computational work provide a rationale for the design of titanium alloys with increased tolerance to variations in interstitial content, with notable implications for more widespread use of titanium alloys.
      Cover page: Mechanistic basis of oxygen sensitivity in titanium
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