Journal
MATERIALS & DESIGN
Volume 152, Issue -, Pages 168-180Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.matdes.2018.04.009
Keywords
Fracture mechanics; Tungsten; Microcantilever testing; EBSD
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Funding
- CCMX through the QuadProbe FIB project
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The loading rate effect on the brittle-ductile transition temperatures of tungsten single crystals at the micro-scale was investigated by microcantilevers with a (100)[001] crack system. Specimens with a length to width to height of 15 mu m/4 mu m/6 mu m were fabricated by focused ion beam milling. At low temperatures (-90 to -25 degrees C) the samples failed by brittle cleavage fracture, irrespective of the applied loading rate at a fracture toughness of 3.2 MPa.m(1/2). With increasing temperatures up to 500 degrees C and depending on the applied loading rate, the fracture toughness increased and significant crack tip plasticity and dislocation-controlled microcleavage were observed by means of high resolution electron backscatter diffraction measurements performed after testing. With respect to macroscopic specimens, a shift of the brittle-ductile transition to lower temperatures and a significantly lower activation energy of the brittle-ductile transition of 0.36 eV were found. We explain this by the increase in flow stresses due to sample size effects. (c) 2018 Elsevier Ltd. All rights reserved.
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