Disordering of L12 Phase in High‐Entropy Alloy Deformed at Cryogenic Temperature

• Published in: Advanced engineering materials Vol. 23; no. 12
• Main Authors: Liu, Hung-Chih, Kuo, Chia-Ming, Shen, Pai-Keng, Huang, Cheng-Yao, Yen, Hung-Wei, Tsai, Che-Wei
• Format: Journal Article
• Language: English
• Published: 01.12.2021
• Subjects: high-entropy alloys; mechanical properties; precipitation strengthening; stacking faults
• ISSN: 1438-1656; 1527-2648
• DOI: 10.1002/adem.202100564

Recently, novel high‐entropy alloys (HEAs) of Al–Co–Cr–Fe–Ni–Ti systems containing face‐centered cubic (FCC) matrix and γ′ precipitates (L12 phase) have been studied. They show superior mechanical properties at room (298 K) and cryogenic temperatures (77 K). Herein, microstructure deformation and fracture after tensile strain are investigated. The results show that multiple‐layered stacking faults occur after the tensile test at 77 K, which can increase the yield strength and ultimate tensile strength by 20% and 24%, respectively. The γ′ precipitates become disordered after the alloy deforms at 77 K, which decreases the formation barrier of mechanical twinning and increases ductility at 77 K by 27%. This study aims at the deformation mechanism of L12 phase in high‐entropy alloys at cryogenic temperature. The results show that the L12 phase becomes disordered after the stacking faults occur. The formation of stacking faults and disordering of L12 phase provide extra strength (≈20%) and ductility (27%), respectively. The alloy shows potential for cryogenic temperature applications.