Abstract
High temperature tensile fracture behavior has been characterized for the nanostructured ferritic alloy 14YWT (SM10 heat). Uniaxial tensile tests were performed at temperatures ranging from room temperature to 1000 °C in vacuum at a nominal strain rate of 10 -3 s -1. Comparing with the existing oxide dispersion strengthened (ODS) steels such as Eurofer 97 and PM2000, the nanostructured alloy showed much higher yield and tensile strength, but with lower elongation. Microstructural characterization for the tested specimens was focused on the details of fracture morphology and mechanism to provide a feedback for process improvement. Below 600 °C, the fracture surfaces exhibited a quasi-brittle behavior presented by a mixture of dimples and cleavage facets. At or above 600 °C, however, the fracture surfaces were fully covered with fine dimples. Above 700 °C dimple formation occurred by sliding and decohesion of grain boundaries. It was notable that numerous microcracks were observed on the side surface of broken specimens. Formation of these microcracks is believed to be the main origin of the poor ductility of 14YWT alloy. It is suggested that a grain boundary strengthening measure is essential to improve the fracture property of the alloy.
Original language | English |
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Pages (from-to) | 143-150 |
Number of pages | 8 |
Journal | Journal of Nuclear Materials |
Volume | 407 |
Issue number | 3 |
DOIs | |
State | Published - Dec 31 2010 |
Funding
This research was performed at the Oak Ridge National Laboratory, Materials Science and Technology Division and sponsored by the Korea Ministry of Knowledge, Visiting Scientists Program, under IAN: 16B642601, with the US Department of Energy. This research was also sponsored by US Department of Energy, Office of Nuclear Energy under Contract DE-AC05-00OR22725 with UT-Battelle, LLC. The authors would like to express special thanks to Drs. J.T. Busby and L. Tan for their technical reviews and thoughtful comments.