The availability of focused ion beam (FIB) milling, nanoindentation, and microelectromechanical systems (MEMS) based test platforms has enabled small-scale mechanical testing to become an increasingly popular approach for measuring material properties. While great emphasis has been placed on measuring plastic properties at the micro- and nanoscale [1, 2], an area that has received significantly less consideration is the measurement of fracture toughness. A technique for performing small-scale, in situ fracture toughness tests using double edge notched tensile (DENT) specimens has been developed and used to measure a nearly 40 % reduction in toughness associated with the addition of Bi to the grain boundary of a Cu bicrystal. That Bi embrittles Cu grain boundaries is well known [3, 4, 5, 6, 7, 8, 9, 10], however, as shown herein, the DENT technique offers certain advantages over existing boundary fracture tests, especially when used with ductile materials.
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The authors would like to acknowledge the financial support provided by NSF grant DMR-0804528. The digital image correlation software was provided by D. Read and N. Barbosa at NIST. The authors would also like to thank the engineers at Hysitron, Inc. for their help and support with the PI-85 system.
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