Mapping the Evolution of Porosity in Sintered Copper to Enable the Numerical Simulation of Sintering
Abstract
The sintering evolution of copper spheres was characterized as part of a larger project with the objective to numerically simulate the sintering of uranium and its alloys to enable the development of sintering models. The larger project is a multi-task activity supported by the U.S. Department of Energy Office of Nuclear Energy where individual tasks included 1) the numerical simulation of sintering in uranium, 2) fundamental atomistic modeling of uranium-zirconium alloys, 3) mapping the actual porosity evolution in sintered uranium-IO wt.% zirconium alloys, and 4) mapping the actual porosity evolution in sintered copper powder pellets. The sintering of copper is a well understood phenomenon, relevant for this project due to its relative metallurgical simplicity as an intermediate modeling challenge. Uranium and U-lOZr exhibit multiple complex phase structures that complicate the ultimate objectives of atomistic and phase field modeling that must eventually be mastered. On the path toward that mastery, copper represents a simple, singlephase face-centered cubic (FCC) structure with a melting point like that of metallic uranium. The high temperature phases for U and U-lOZr are body-centered cubic (BCC), which make this material more challenging to cut and polish for porosity analysis. For this reason, Cu powder was used to prepare microstructure data for mapping porosity evolution during sintering and provide a simpler validation point for numerical simulations of the porosity evolution in two-phase U-lOZr.
The work presented here describes the experimental methods developed for the generation of sintered, porous copper metal pellets and the volumetric porosity distribution for set temperature. This involved the evaluation and determination of production parameters for palletization such as pressure, lubrication, sintering temperature, and dwell time. An initial series of sintering tests were performed to establish pressing and sintering parameters; sintering of pressed pellets and packed powder-bed pellets was evaluated. Eventually, a systematic set of samples was created by sintering samples at 1065°C. The sintered pellets were characterized to map the evolution of density and porosity during sintering. a porosity gradient formed within the pellet. The sintered structures exhibited a 2-region characteristic where the outer region exhibited minimal densification with some with particle bonding while the interior region exhibited high levels of densification. The evolution of this two-region structure was evaluated.
Subject
Copper sinteringCitation
Salazar, Yesenia (2021). Mapping the Evolution of Porosity in Sintered Copper to Enable the Numerical Simulation of Sintering. Master's thesis, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /196114.