Compressive Properties of Nanoporous Gold Through Nanoindentation: An Analytical Approach Based on the Expanding Cavity Model

• Published in: Metals and materials international Vol. 27; no. 10; pp. 3787 - 3795
• Main Authors: Kwon, Oh Min, Kim, Jiyeon, Lee, Jinwoo, Kim, Jong-hyoung, Ahn, Hee-Jun, Kim, Ju-Young, Kim, Young-Cheon, Kwon, Dongil
• Format: Journal Article
• Language: English
• Published: Seoul The Korean Institute of Metals and Materials 01.10.2021; Springer Nature B.V; 대한금속·재료학회
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Compressive properties; Core hardenability; Densification; Engineering Thermodynamics; Galvanic corrosion; Gold; Heat and Mass Transfer; Heat treatment; Machines; Magnetic Materials; Magnetism; Manufacturing; Materials Science; Metallic Materials; Morphology; Nanoindentation; Processes; Scaling factors; Solid Mechanics; Strain hardening; Yield strength; Yield stress; 재료공학; Nanoporous gold; Hardness; Yield stress; Nano-indentation
• ISSN: 1598-9623; 2005-4149
• DOI: 10.1007/s12540-020-00740-7

We investigated the analytic relation between hardness and compressive yield stress using an expanding cavity model (ECM) for nanoporous gold (np-Au). We prepared three np-Au samples with ligament sizes 30.61, 59.36 and 116.33 nm by free-corrosion dealloying and post heat treatment. The indentation contact morphology was examined to estimate the hardness accurately from the nanoindentation load-depth curve. Unlike conventional dense metals, the deformation was confined to the projected contact area, and the center of the residual impression was dominated by densification. The projected contact area estimated by the Oliver–Pharr method was overestimated, so that a new contact area function was proposed that considered the indentation contact morphology of np-Au. It was confirmed that a hardness value taking into account the indentation contact morphology of np-Au matches well with the hardness derived by direct measurement of the residual impression. We modeled the ratio of hardness to compressive yield stress for np-Au using an ECM. The scaling factors, which represent the extra strain-hardening in the core in the ECM, were analyzed for np-Au and dense metals. An ECM that better matches np-Au is suggested based on the scaling factor resulting from densification beneath the indenter. Graphic abstract