The influence of grain boundary area on the complexion time-temperature-transformation diagram of Eu-doped magnesium aluminate spinel

摘要

We demonstrate the sensitivity of complexion time-temperature-transformation (TTT)-diagrams to composition and grain size in Eu-doped MgAl2O4. 100 ppm and 500 ppm Eu-doped MgAl2O4 undergo the same complexion transition, which causes abnormal grain growth, but exhibit different nucleation and grain growth rates. The Eu content per grain boundary area (Eu/GBA) was calculated for various heat treatments using a simple model based on average grain size. Despite their differences, a common Eu/GBA is calculated at the onset of abnormal grain growth. This common grain boundary excess has important implications for complexion TTT-diagrams and provides a new metric for predicting abnormal grain growth. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.