Influence of grain boundaries on mechanical behavior at ultra-high strain rates and low temperatures

This project aims to investigate the influence of grain boundaries on mechanical behavior at ultra-high strain rates and low temperatures.

It was recently discovered that the strain rate sensitivity of metallic bicrystals, with isolated twin or grain boundaries, differs from single crystals at quasi-static strain rates via micropillar compression [1]. However, it is known that at higher strain rates the yield strength and deformation mechanism of materials changes significantly [2]. So far, the influence of individual grain boundaries on the rate-dependent behavior of metals remains largely unexplored. Additionally, the influence of temperature on the grain boundary interaction with dislocations and its influence on the mechanical response of metals also remain open for investigation. New developments in micromechanical testing equipment now enable displacement-controlled micropillar compressions in the ultra-high strain rate regime (upto 10000/s) [3], at low temperatures [4], and also combined high strain rate and cryogenic conditions [5].

Using such a novel small-scale mechanical testing device, this project aims to unravel the mysteries of grain boundary interactions at ultra-high strain rates and low temperatures using bicrystal micropillar compression testing of copper.

Malyar, N. V.; Grabowski, B.; Dehm, G.; Kirchlechner, C.: Dislocation slip transmission through a coherent Σ3{111} copper twin boundary: Strain rate sensitivity, activation volume and strength distribution function. Acta Materialia 161, pp. 412 - 419 (2018)
Edington, J. W.
The influence of strain rate on the mechanical properties and dislocation substructure in deformed copper single crystals
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G. Guillonneau, M. Mieszala, J. Wehrs, J. Schwiedrzik, S. Grop, D. Frey, L. Philippe, J.-M. Breguet, J. Michler, J.M. Wheeler
Nanomechanical testing at high strain rates: New instrumentation for nanoindentation and microcompression
Mater. Des. 148, 39 (2018)
Ast, J.J. Schwiedrzik, J. Wehrs, D. Frey, M.N. Polyakov, J. Michler, X. Maeder
The brittle-ductile transition of tungsten single crystals at the micro-scale
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Schwiedrzik, J. J.; Ramachandramoorthy, R.; Edwards, T. E. J.; Schürch, P.; Casari, D.; Duarte, M. J.; Mohanty, G.; Dehm, G.; Maeder, X.; Philippe, L. et al.; Breguet, J.-M.; Michler, J. K.: Dynamic cryo-mechanical properties of additively manufactured nanocrystalline nickel 3D microarchitectures. Materials & Design 220, 110836 (2022)

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