In recent years, access to and use of focused ion beam (FIB) techniques have increased, leading to new research opportunities in the field of nanoporous (np) metals. Direct observation of sub surfaces and 3D reconstructions are now possible, refining our knowledge of the np structure and its behavior. Because np metals in bulk form are typically challenging to fabricate and classic mechanical testing techniques (tension/compression tests) difficult to implement, several studies used nanoindentation to obtain mechanical properties. However, the deformation behavior of network structures of this scale (pores and ligaments in tens of nm) has yet to be fully understood. During this talk, we will show how the np structure accommodates the imposed deformation, by presenting cross section images and 3D reconstructions of np-Au after nanoindentation testing.
We have used np-Au as a model material to directly characterize the mechanical response of a np metal structure during nanoindentation. We have prepare bulk np-Au specimens and imaged the sub surface under indents, after FIB cross sectioning. In addition, we have automated FIB milling and imaging steps and were able to reconstruct indented regions, in 3D. Results from this study indicated that np-Au behaves more like a dense metal during nanoindentation, with the deformation propagating far ahead of the indenter, without full densification of the np structure. This observation and its implications will be discussed and compared with results previously obtained from millimeter-scale tensile and compression testing on np-Au.