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Revealing the micromechanisms behind semi-solid metal deformation with time-resolved X-ray tomography.

ABSTRACT: The behaviour of granular solid-liquid mixtures is key when deforming a wide range of materials from cornstarch slurries to soils, rock and magma flows. Here we demonstrate that treating semi-solid alloys as a granular fluid is critical to understanding flow behaviour and defect formation during casting. Using synchrotron X-ray tomography, we directly measure the discrete grain response during uniaxial compression. We show that the stress-strain response at 64-93% solid is due to the shear-induced dilation of discrete rearranging grains. This leads to the counter-intuitive result that, in unfed samples, compression can open internal pores and draw the free surface into the liquid, resulting in cracking. A soil mechanics approach shows that, irrespective of initial solid fraction, the solid packing density moves towards a constant value during deformation, consistent with the existence of a critical state in mushy alloys analogous to soils.

SUBMITTER: Kareh KM

PROVIDER: S-EPMC4109016 | biostudies-literature | 2014 Jul

REPOSITORIES: biostudies-literature

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Revealing the micromechanisms behind semi-solid metal deformation with time-resolved X-ray tomography.

Kareh K M KM Lee P D PD Atwood R C RC Connolley T T Gourlay C M CM

Nature communications 20140718

The behaviour of granular solid-liquid mixtures is key when deforming a wide range of materials from cornstarch slurries to soils, rock and magma flows. Here we demonstrate that treating semi-solid alloys as a granular fluid is critical to understanding flow behaviour and defect formation during casting. Using synchrotron X-ray tomography, we directly measure the discrete grain response during uniaxial compression. We show that the stress-strain response at 64-93% solid is due to the shear-induc ...[more]

PMID: 25034408

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