Competition between continuous and discontinuous precipitation in L12-strengthened high-entropy alloys. (October 2022)

• Record Type: Journal Article
• Authors: Fang, J.Y.C.; Liu, W.H.; Luan, J.H.; Yang, T.; Wu, Y.; Fu, M.W.; Jiao, Z.B.
• Is Part Of: Intermetallics. Volume 149(2022)
• Publication Date: 2022-10
• Subjects: High-entropy alloy -- L12 precipitate -- Continuous precipitation -- Discontinuous precipitation -- Temperature effect; Intermetallic compounds -- Metallography -- Periodicals; Metallic glasses -- Periodicals; Composés intermétalliques -- Métallographie -- Périodiques; 669.94
• DOI: 10.1016/j.intermet.2022.107655
• Languages: English
• ISSNs: 0966-9795

Abstract

Abstract: Understanding of the competition between continuous precipitation (CP) and discontinuous precipitation (DP) is crucial for tailoring the microstructure and mechanical properties of precipitation-strengthened high-entropy alloys (HEAs). In this study, the effects of aging temperature, aging time, and grain size on the CP and DP behaviors of L12 -strengthened HEAs were systematically investigated. Our results reveal that low temperatures favor the DP reaction while high temperatures facilitate the CP reaction, which is related to the nucleation site and diffusion path of the two precipitation modes. At intermediate temperatures, both the CP and DP occur simultaneously and compete with each other, and the solute concentration difference across the boundaries between the two precipitation regions serves as the driving force for the sweeping of the CP regions by the DP reaction. In addition, grain size refinement can promote the DP reaction by providing more nucleation sites and more fast diffusion paths, leading to the formation of the DP-dominant microstructure. This study not only sheds light on the fundamental understanding of the CP and DP mechanisms but also provides useful guidelines for the microstructure design of advanced L12 -strengthened HEAs. Graphical abstract: Image 1 Highlights: Continuous and discontinuous precipitation in high-entropy alloys were studied. Low aging temperatures favor the discontinuous precipitation of L12 precipitates. High temperatures facilitate the continuous precipitation of L12 precipitates. Grain size refinement promotes the discontinuous precipitation of L12 precipitates. The discontinuous precipitation proceeds by sweeping the continuous precipitates.