Microstructure and Mechanical Properties of New AlCoxCrFeMo0.5Ni High-Entropy Alloys

• Published in: Advanced engineering materials 2010-02, Vol.12 (1-2), p.44-49
• Main Authors: Hsu, Chin-You, Wang, Woei-Ren, Tang, Wei-Yeh, Chen, Swe-Kai, Yeh, Jien-Wei
• Format: Article
• Language: English
• ISSN: 1438-1656; 1527-2648
• DOI: 10.1002/adem.200900171

Effects of Co content on microstructures and hot hardness of a new high‐entropy alloy system, AlCoxCrFeMo0.5Ni (x = 0.5 to 2.0) were investigated. As cobalt content increases, the microstructure changes from dendrite to polygrain type and the constituent phases change from BCC + σ at x = 0.5 to BCC + FCC + σ at x = 2.0. The alloy hardness varies from Hv 788 at x = 0.5 to Hv 596 at x = 2.0. This can be explained with the relative amount of hard σ phase, medium hard BCC phase and soft FCC phase. All the AlCoxCrFeMo0.5Ni alloys possess higher hardness level than that of Ni‐based superalloys In 718/In 718 H from room temperature to 1273 K. They obey the Westbrook equation presenting the normal heating behavior. Both alloys of x = 0.5 and 1.0 exhibit a transition temperature higher than that of Co‐based alloy T‐800 by about 200 K. They also have a high hot hardness of Hv 347 at 1273 K, which is higher than those of In 718 and In718 H by Hv 220. The strengthening mechanism for their superiority is proposed. The AlCoxCrFeMo0.5Ni alloy system has great potential in high‐temperature applications. Effects of Co content on microstructures and hot hardness of a new high‐entropy alloy system, AlCoxCrFeMo0.5Ni (x = 0.5 to 2.0, in molar ratio) were investigated. All the AlCoxCrFeMo0.5Ni alloys possess higher hardness level than that of Ni‐based superalloys In 718/In 718 H from room temperature to 1273 K, indicating that this alloy system has great potential in high‐temperature applications.