Mechanics of sintering materials with bimodal pore distribution. III. Kinetics of sintering combined with various forms of loading and adhesion conditions

Abstract

621.762A study has been made on the effects of loading scheme and conditions restricting macroscopic strain on the work-hardening kinetics and strain accumulation in the solid state in sintering materials with bimodal pore size distributions. Active loading intensifies the reduction in the small pores. The greatest effect comes from combining sintering with hydrostatic compression. At the same time, kinematic constraints (partial or complete adhesion in surfaces) substantially retards the shrinkage of large pores, which means that the porous structure can be controlled.

Impact of Thermal Diffusion on Densification During SPS

“…For the development of an SPS model framework, we use the concepts of the continuum theory of sintering 38,57–79 : where σ ij and correspond to stress tensor and strain rate tensor components, respectively; W is the “equivalent strain rate”, σ( W ) is the “equivalent stress” responsible for the constitutive behavior of a porous material; ϕ and ψ are the normalized shear and bulk viscosities; and δ ij is the Kronecker symbol (δ ij =1 if i = j and δ ij =1 if i ≠ j ). Effective equivalent strain rate W depends on the invariants of the strain rate tensor: …”

Sintering stability of biporous materials under kinematic constraints

“…However, a model containing porosity as the only parameter fails to describe differential shrinkage. The results discussed here as well as those reported in [1,4,6,8] are based on the assumption that a material sintered has pores of two types: large and small. Nevertheless, this paper differs from the cited publications, which were restricted to homogeneous pore distribution, by focusing on the volume distribution of each type of pores.…”

“…The sintering kinetics of a biporous material combined with different loading cases and constraining conditions was examined in [4] for homogenous distribution of large and small pores. Similar phenomena were also considered in [16][17][18].…”

Consolidation of ceramic nanopowders

“…Grounded on rheological theory, the computer modeling has given the kinetic dependences of densification for the porous linearly viscous body calculated for the various modes of loading such as free densification in the regime of SF, uniaxial compression in a rigid matrix and hydrostatic compression in a high pressure apparatus. 9 The results of calculations presented in Fig. 2 are useful to predict densification rather than the structure evolution in the pore and grain subsystems of a nanostructured material.…”