Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
7983366 | Materials Science and Engineering: A | 2013 | 11 Pages |
Abstract
Spark plasma sintering was used to process bulk ultrafine-grained (average grain size of â¼250Â nm) samples from high purity nanocrystalline Zn powder. The microstructure of the consolidated samples was investigated and the mechanical behaviour was characterised by means of quasistatic and dynamic compression tests at room temperature and compared to that of coarse-grained counterparts. For both materials in the strain rate regime of 10â4-101Â sâ1 a linear relationship between the logarithm of flow stress and strain rate values was observed since room temperature corresponds to a relatively high homologous temperature of 0.43. The strain rate sensitivity was higher for ultrafine-grained Zn (â¼0.18) than for coarse-grained Zn (â¼0.12) and twinning in the former sample was not observed in the entire strain rate range. For strain rates higher than 103Â sâ1 the plasticity in coarse-grained Zn was controlled by dislocation drag but partial recrystallization was also observed. In the latter regime the mobile dislocation density was about 1011Â mâ2. However, in ultrafine-grained Zn the relatively large dislocation density (â¼1014Â mâ2) and the small grain size limit the dislocation velocity yielding the lack of dislocation drag effects up to 104Â sâ1.
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Physical Sciences and Engineering
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Authors
G. Dirras, J. Gubicza, H. Couque, A. Ouarem, P. Jenei,