The interaction of dislocation pile-ups with several tilt grain boundaries (GB) is studied in copper by using a hybrid continuum-atomistic approach. The effects of temperature, pile-up intensity and GB structure on absorption and transmission of slip as a function of local stress state are explored. By considering several high-angle GBs with different misorientation angles, we demonstrate that GB atomic structure primarily defines its ability to accommodate incoming pile-up dislocations, thus limiting the direct transmission of pile-ups through the interface.
Konyashin, I.; Lachmann, F.; Ries, B.; Mazilkin, A.; Straumal, B.; Kübel, C.; Llanes, L.; Baretzky, B. Scripta materialia Vol. 83, p. 17-20 DOI: 10.1016/j.scriptamat.2014.03.026 Data de publicació: 2014-07-15 Article en revista
For conventional structural and tool materials, in particular WC-Co cemented carbides, hardness and wear-resistance can usually be increased only at the expense of toughness and strength. For the first time we have achieved a dramatically increased combination of hardness, wear-resistance, fracture toughness and strength as a result of precipitation of extremely fine nanoparticles in the cobalt binder of cemented carbides. These nanoparticles are similar to 3 nm in size, coherent with the Co matrix and consist of a metastable phase. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
In this work, the applicability of the two most commonly used equations for calculating the fracture toughness by nanoindentation is discussed in terms of the indenter geometry and the indentation crack morphology. These equations are calibrated for Berkovich and cube-corner indenters taking into account the actual indentation crack morphology, aimed at attaining a more reliable estimation of fracture toughness in small material volumes by nanoindentation.
Tejedor, R.; Rodriguez-Baracada, R.; Benito, J.; Caro, J.; Cabrera, J.; Prado, J. Scripta materialia Vol. 59, num. 6, p. 631-634 DOI: 10.1016/j.scriptamat.2008.05.024 Data de publicació: 2008-09 Article en revista
The strain rate sensitivity of three steels with carbon contents ranging from 0.05 to 0.55 wt.% has been determined by nanoindentation and compression tests in the nanocrystalline and ultrafine-grained ranges. Samples were obtained by warm consolidation from milled powders. In the nanocrystalline range the steel with higher carbon content was found to be slightly rate sensitive, which means that the presence of carbon involves a change in the deformation mechanism of body-centered cubic iron, resulting in grain boundaries contributing to the plasticity.