Modification of Precipitate Coarsening Kinetics by Intragranular Nanoparticles—A Phase Field Study

Abstract

Precipitate coarsening is a major mechanism responsible for the degradation in mechanical properties of many precipitation-hardened alloys at high temperatures. With recent developments in processing of nanocomposite materials, a substantial volume fraction of inert second phase ceramic nanoparticles can be introduced into the grain interiors of polycrystalline materials. These intragranular nanoparticles can have synergistic effects of impeding dislocation motion and interacting with coarsening precipitates to modify the coarsening rate. In this work, the precipitate coarsening behavior of an alloy in the presence of intragranular inert nanoparticles was studied using the phase field method. Two key measurements of coarsening kinetics, precipitate size distribution and coarsening rate, were found to be affected by the volume fraction and the size of nanoparticles. Two novel mechanisms related to geometric constraints imposed by inter-nanoparticle distance and the blockage of solute diffusion path by nanoparticle–matrix interfaces were proposed to explain the observed changes in precipitate coarsening kinetics. The simulation results in general suggest that the use of small nanoparticles with large number density is effective in slowing down the coarsening kinetics.

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“…All the other precipitates have mean radius of less than 3.26nm. From Figures 6 and 7, the graphs show that precipitate mean radius of phases decreases with increasing phase fractions and vice versa, which corroborates findings in literature [30].…”

“…Precipitation simulation is set to capture changes in temperature, number density, phase fractions and mean radii of precipitates. Number density, phase fractions and precipitate mean radii are known to affect coarsening behaviour of alloys and influence strength [29], [30].…”