Quantifying dislocation drag at high strain rates with laser-induced Microprojectile impact

Tang, Qi; Hassani, Mostafa

doi:10.1016/j.ijplas.2024.103924

Cited by 2 publications

(1 citation statement)

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“…The drag mechanisms that prevail under high rates are interesting because they are not rate limited in the same manner as the thermally activated mechanisms described above; they are instead expected to be a mode of ballistic dislocation transport. It has been anticipated that, in this extreme range, metals indeed may not soften at high temperatures 4 , 16 , 20 , 21 , a behaviour that is counterintuitive and at odds with decades of studies in less extreme conditions.…”

Section: Mainmentioning

confidence: 99%

Metals strengthen with increasing temperature at extreme strain rates

Dowding,

Schuh

2024

Nature

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The strength of materials depends on the rate at which they are tested, as defects, for example dislocations, that move in response to applied strains have intrinsic kinetic limitations1–4. As the deformation strain rate increases, more strengthening mechanisms become active and increase the strength4–7. However, the regime in which this transition happens has been difficult to access with traditional micromechanical strength measurements. Here, with microballistic impact testing at strain rates greater than 106 s−1, and without shock conflation, we show that the strength of copper increases by about 30% for a 157 °C increase in temperature, an effect also observed in pure titanium and gold. This effect is counterintuitive, as almost all materials soften when heated under normal conditions. This anomalous thermal strengthening across several pure metals is the result of a change in the controlling deformation mechanism from thermally activated strengthening to ballistic transport of dislocations, which experience drag through phonon interactions1,8–10. These results point to a pathway to better model and predict materials properties under various extreme strain rate conditions, from high-speed manufacturing operations11 to hypersonic transport12.

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Section: Mainmentioning

confidence: 99%