• Bordia, Rajendra
• Giuntini, Diletta
• Molinari, Alberto
• Vecchio, Kenneth
• Zhu, Chaoyi
• Olevsky, Eugene
• Torresani, Elisa
• Harrington, Tyler

Abstract

A micromechanical model for the shrinkage anisotropy during sintering of metallic powders is<br/>proposed and experimentally assessed. The framework developed for modeling sintering based<br/>on the mechanism of grain boundary diffusion is extended to take into account the dislocation<br/>pipe-enhanced volume diffusion. The studied iron powder samples are pre-shaped into their<br/>green forms by uniaxial cold pressing before sintering step. The resultant green bodies are<br/>anisotropic porous structures, with inhomogeneous plastic deformation at the inter-particle<br/>contacts. These non-uniformities are considered to be the cause of the anisotropic dislocation<br/>pipe diffusion mechanisms, and thus of the undesired shape distortion during shrinkage. The<br/>proposed model describes the shrinkage rates in the compaction loading and transverse<br/>directions, as functions of both structural and geometric activities of the samples. Dislocation<br/>densities can be estimated from such equations using dilatometry and image analysis data. The<br/>reliability and applicability of the developed modeling framework are verified by comparing the<br/>calculated dislocation densities with outcomes of nanoindentation and electron backscatter<br/>diffraction-derived lattice rotations.

Topics

• porous
• impedance spectroscopy
• pore
• polymer
• grain
• grain boundary
• anisotropic
• nanoindentation
• dislocation
• iron
• sintering
• dilatometry
• iron powder