Mechanical Scaling Laws and Deformation Behavior of Nanoporous Tantalum Microparticles
The mechanical scaling laws of dealloyed nanoporous metals depart from classical Gibson-Ashby predictions for open-cell foams due to a decreased connectivity in their solid network. However, these scaling relations have been established almost exclusively on nanoporous gold produced by electrochemical dealloying, and it is an outstanding question whether the relations apply to nanoporous networks fabricated by other dealloying methods. Here, we investigate the mechanical response of single-crystalline nanoporous tantalum (np-Ta) produced by liquid metal dealloying (LMD) a TiTa alloy in molten CuBi. Nanoindentation of individual microparticles yields an elastic modulus of 10-30 GPa and a hardness of 0.3-1.1 GPa, both scaling with the solid volume fraction in agreement with Gibson-Ashby predictions. This stiffness-density response of np-Ta departs from previous reports on nanoporous gold and is attributed to enhanced ligament connectivity enabled by the thermodynamics of the CuBi metal bath. Molecular dynamics simulations reveal dislocation-dominated plasticity during indentation of np-Ta, consistent with scanning electron microscopy observations of limited densification beneath the indents, ruling out unusual deformation mechanisms as an origin of the observed scaling. These findings identify solvent chemistry in LMD as a tunable lever for ligament connectivity, and thus for the mechanical response of nanoporous metals.