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Sintering 2017 Plenary Speakers

 

Didier Bouvard,  Univ. Grenoble Alpes, France

 

Title: Investigating the sintering of multilayer components with advanced experimental and modelling tools

 

Abstract: Powder processing is particularly appropriate to the fabrication of multilayer components, possibly including both ceramic and metal layers. However, due to the different sintering behaviors of the stacked materials, stresses develop during heating, sintering or cooling, which affect dimensional changes and may damage the materials. Thus obtaining near net-shape and defectless components is often challenging. Coupling adapted experimental work and model development has proven to be valuable for better understanding and optimizing the sintering of such components.

 
Three examples of such efforts are presented. They concern, respectively, SOFC stacks comprising porous and dense layers, which often exhibits cambering during sintering, two-layer ceramic-metal parts that crack during heating and multilayer ceramic capacitors that develop local defects in the course of sintering. Appropriate experimental tools include optical dilatometry and computed microtomography whereas modelling tools comprise finite element analysis and discrete element method.

 

 

 

 

 

Martin Harmer, Lehigh University, Bethlehem, Pennsylvania, USA

 

Title: Know your boundaries

 

Abstract: Do you know that grain boundaries can behave in a “phase-like “ manner and undergo transformations that can dramatically influence the sintering behavior and properties of a material? Do you know that grain boundaries exhibit time-temperature-transformation (TTT) characteristics like steels? Do you know how to exploit grain boundary TTT diagrams in sintering? Do you know how “two-step” sintering and “flash” sintering work? Do you know about “anti-thermal” behavior of grain growth? Do you want a glimpse into the future of data-driven scientific discovery in sintering? I don’t have all the answers, but if these sorts of questions interest you, then you may want to come to this talk.

 

 

 

 

 

 

Bernd Kieback, Fraunhofer-Institut für Fertigungstechnik und Angewandte Materialforschung IFAM, Institutsteil Dresden, GERMANY

 

Title: Contact formation and densification during early stages of spark plasma sintering of metal powders

 

Abstract: The role of the electric field and electric current during Spark Plasma Sintering of metallic powders were discussed in numerous publications with the aim to explain the fast densification in this technique. The aim of the current paper is a systematic analysis of the conditions and processes during pulsed current sintering on a microscopic scale. Based on typical electric parameters and applied pressures during SPS the role of electric currents, temperature fields and stress distributions were analyzed by simulation and model experiments using spherical metal powders. The results show, that only at extreme conditions contact melting happens at the particle contacts. The role of temperature gradients, electric field and current distribution on contact formation will be discussed in detail. Using the two particle model for the early stages of sintering, the growth of contacts and shrinkage will be discussed for various mechanisms: curvature driven diffusion, pressure assisted sintering, creep deformation of particle contact areas. The results show, that some of the processes proposed for SPS do not contribute in a significant way. Although the experimental results were obtained only for copper and steel powders, the discussion should help give a realistic view also for other systems and process conditions.


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