• Schmalbach, Kevin
• Wang, Zhao
• Poerschke, David
• Penn, R. Lee
• Antoniou, Antonia
• Mara, Nathan A.
• Stein, Andreas

Abstract

<p>Porous metals represent a class of materials where the interplay of ligament length, width, node structure, and local geometry/curvature offers a rich parameter space for the study of critical length scales on mechanical behavior. Colloidal crystal templating of three-dimensionally ordered macroporous (3DOM, i.e., inverse opal) tungsten provides a unique structure to investigate the mechanical behavior at small length scales across the brittle-ductile transition. Micropillar compression tests show failure at 50 MPa contact pressure at 30 °C, implying a ligament yield strength of approximately 6.1 GPa for a structure with 5% relative density. In situ SEM frustum indentation tests with in-plane strain maps perpendicular to loading indicate local compressive strains of approximately 2% at failure at 30 °C. Increased sustained contact pressure is observed at 225 °C, although large (20%) nonlocal strains appear at 125 °C. The elevatederature mechanical performance is limited by cracks that initiate on planes of greatest shear under the indenter.</p>

Topics

• porous
• density
• impedance spectroscopy
• scanning electron microscopy
• crack
• strength
• compression test
• yield strength
• tungsten