Synthesis of dense titanium carbide-titanium based cermets via self-propagating high temperature synthesis and quasi-isostatic pressing.

摘要

This study focuses on the fabrication of near net-shape Titanium Carbide-Titanium (TiC-Ti) cermets via SHS process followed by quasi-static pressing of the cermets in a Pressure Transmitting Medium (PTM) (the cermets are surrounded by the PTM and both the cermets and the PTM are loaded in a rigid die).; The first part of this study is the theoretical modeling of the QIP process. The shape distortion and densification of the cermets are the main concerns. Different models for the shear modulus 4 and the bulk modulus psi of the cermets were investigated and compared. The results show that Skorohod models for the shear and bulk moduli provide the best agreement between theoretical and experimental results. Thereafter, the post-combustion pressing of the cermets in a die with the surrounding PTM (QIP processing) was modeled. As a first approximation, a poro-elastic model describing the mechanical behavior of the PTM under compression was created. It was also determined that the power law creep models described satisfactorily the constitutive behavior of the cermets themselves under a compression load. An indentation experiment was carried out in order to determine the power law creep materials' constants A and m for the cermets. Based on the understanding of the constitutive behavior of both the cermets and the PTM, the QIP process applied to the cermets was successfully modeled.; Following the theoretical modeling, a series of combustion experiments were conducted. The best non-stoichiometric ratio of titanium and graphite for the preparation of green samples was found. The time delay between the end of the combustion and the start of consolidation was investigated. The relationship between the consolidation load and the distortion of the cermets was also analyzed.; Finally, a finite element simulation of the deformation and densification of the cermets was carried out. For the purpose of comparison, the commercial FEA package ABAQUS was also used for the simulation. It was found that the Mohr-Coulomb and the Cap plasticity models for PTM provide the better agreement with the experiment results.