Mechanical properties and microstructure evolution of Ti2AlC under compression in 25–1100 °C temperature range

• Published in: Acta materialia 2020-05, Vol.189, p.154-165
• Main Authors: Benitez, R., Kan, W.H., Gao, H., O'Neal, M., Proust, G., Srivastava, A., Radovic, M.
• Format: Article
• Language: English
• Subjects: Creep; Grain boundary sliding; Grain refinement; Hall-Petch effect; MAX phases
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2020.02.057

This study investigates the effects of the initial grain size and temperature (ranging from room temperature to 1100 °C) on the mechanical properties and microstructure evolution of Ti2AlC MAX phase. A Hall-Petch like relationship is observed between compressive strength and the grain size below brittle-to-plastic transition temperature (BPTT). However, the compressive strength of fine-grained MAX phase decreases more rapidly with increasing temperature resulting in inverse Hall-Petch effect above BPTT. Results from postmortem EBSD analysis reveal complex microstructural evolution in both fine- and coarse-grained microstructures during loading at different temperatures. The pronounced drop in compressive strength for fine-grained microstructures at temperatures close to BPTT is attributed to creep induced grain boundary sliding resulting in texture development with more grains oriented for easy slip. In coarse-grained microstructures, no significant texture development is observed even though grain refinement occurs at all temperatures. A mathematical model has also been formulated to predict the experimentally observed grain size and temperature dependent variation in the compressive strength of Ti2AlC over a wide range of grain sizes and test temperatures. The mathematical model accounts for the competing effects of Hall-Petch strengthening and high temperature creep induced softening mechanisms. [Display omitted]