High heating rate effects in sintering: A phase-field study of La-doped alumina

TL;DR

This work tackles the challenge of optimizing high heating rate sintering by introducing a representative multiphysics phase-field framework that resolves both microstructure and temperature evolution on a particle scale. The model couples a phase-field description (MPF/KKS) with a vacancy-driven grain-motion mechanism and a novel particle-based temperature model, enabling simulations of densification and grain growth under rapid heating and the emergence of a sintering front. Comparisons with experimental data show reasonable agreement without parameter fitting, and the simulations reveal how temperature inhomogeneity propagates microstructural differences via a Biot-number criterion. The findings provide a pathway for designing practical heating schedules for novel materials, illustrating when and how temperature gradients influence densification and grain growth during high-rate sintering.

Abstract

Sintering is a widespread manufacturing process, accounting for a significant portion of global energy expenditure. However, controlling this process has been mostly a trial-and-error process, being costly in both time and money. The recent advance of high heating rate sintering methods, which promise higher energy efficiency and better properties, only adds to this. This paper aims to reduce these costs by shedding light on the microstructural evolution during high heating rate sintering, which will allow for quicker parameter optimization and improved properties. The focus will be on how a representative microstructure changes locally as well as globally while resolving grains and the green body at scale, which no prior paper has done. A representative multiphysics phase-field solver is employed, incorporating a novel particle-based temperature model, which recovered many characteristics typical of high heating rate sintering. Comparing the simulation data to experimental data showed reasonable agreement over a large density range without parameter adjustment. Furthermore, the advance of a sintering front including grain growth effects could be shown simulatively for the first time in literature. These findings suggest that the model can be used for the design of practical heating schedules for the sintering of novel materials.

Figures (11)

• Figure 1: Transformation from grid-wise temperature to particle-wise temperature. Red dots indicate a degree of freedom and blue lines indicate the degree's boundaries.
• Figure 2: The initial green body configuration is depicted.
• Figure 3: Exemplary microstructures at approximately $90\%$ density are depicted. Note the much larger grains for slower heating rates.
• Figure 4: Two trajectory types for high-heating rate sintering at a constant heating rate and homogeneous temperature are shown. The qualitative trends of experiments are generally captured, except for the lowest heating rate showing a crossover with higher heating rates at higher density.
• Figure 5: Density-densification rate trajectories for the present simulations as well as experimental data from literature. The trajectory is generally concave, showing its maximum around $80\%$ density. The experimental curve for 350K/s is of the same order-of-magnitude as the simulations which bound this heating rate.