Simultaneous Strength-Ductility Enhancement of a Nano-Lamellar AlCoCrFeNi 2.1 Eutectic High Entropy Alloy by Cryo-Rolling and Annealing

• Published in: Scientific reports Vol. 8; no. 1; p. 3276
• Main Authors: Bhattacharjee, T, Wani, I S, Sheikh, S, Clark, I T, Okawa, T, Guo, S, Bhattacharjee, P P, Tsuji, N
• Format: Journal Article
• Language: English
• Published: England 19-02-2018
• ISSN: 2045-2322

Nano-lamellar (L1
 + B2) AlCoCrFeNi
eutectic high entropy alloy (EHEA) was processed by cryo-rolling and annealing. The EHEA developed a novel hierarchical microstructure featured by fine lamellar regions consisting of FCC lamellae filled with ultrafine FCC grains (average size ~200-250 nm) and B2 lamellae, and coarse non-lamellar regions consisting of ultrafine FCC (average size ~200-250 nm), few coarse recrystallized FCC grains and rather coarse unrecrystallized B2 phase (~2.5 µm). This complex and hierarchical microstructure originated from differences in strain-partitioning amongst the constituent phases, affecting the driving force for recrystallization. The hierarchical microstructure of the cryo-rolled and annealed material resulted in simultaneous enhancement in strength (Yield Strength/YS: 1437 ± 26 MPa, Ultimate Tensile Strength/UTS: 1562 ± 33 MPa) and ductility (elongation to failure/e
 ~ 14 ± 1%) as compared to the as-cast as well as cold-rolled and annealed materials. The present study for the first time demonstrated that cryo-deformation and annealing could be a novel microstructural design strategy for overcoming strength-ductility trade off in multiphase high entropy alloys.