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Constitutive Modeling and Simulation of Spark Plasma Sintering with Applications to Fabrication of Functionally Structured Mono-Carbides

Abstract

The so called spark plasma sintering (SPS) is a relatively new hot consolidation technology that is getting rapidly growing attention for the academic research and industrial development. Although there is no evidence of plasma existence yet, substantial experiment trials have been done and often delivered superior material properties with high processing efficiency. However, the majority of fundamental modeling and simulation work done to now is still limited to the study on interactions of electrical- thermal fields; while few of the studies included analyses of stress distribution, densification, or grain growth. This study is the first modeling and simulation work to fully couple electrical-thermal-mechanical fields together with porous body consolidation and grain growth. This study uses a power law creep based model with a novel grain size - density correlation model to describe the material densification and microstructure coarsening under mechanical pressure at high temperature. Realistic boundary conditions at the contact interfaces between punch-die-specimen are also included in calculations. A novel multi step pressure dilatometry approach is introduced to determine the material parameters for modeling, including strain rate sensitivity (responsible for hardening effect), activation energy, and the vibrational frequency. With the experimentally determined material parameters and handbook properties, the model predictions are close to experimental density data on SPS of copper (R2 90.4%) and vanadium carbide (R2 99.7%) powders. Copper was used for the fundamental study with the aim to characterize electric current impact on SPS consolidation. Another system of vanadium carbide was used as a surrogate material with the aim to investigate the feasibility of fabricating functionally structured uranium carbide nuclear fuel pellets by SPS

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