Theoretical predict the structure, elastic anisotropy and thermodynamic properties of Al5W in Al-rich region

Abstract

Al5W compound is a promising high-temperature material due to the high melting point, good mechanical properties and good corrosion resistance. However, the structural feature of Al5W remains controversy. To solve these problems, we apply the first-principles calculations to study the structural stability, elastic properties, elastic anisotropy and melting point of Al5W. Four possible Al5W phases are discussed based on the similar A5B-type structure. The results show that two novel Al5W phases: orthorhombic (Cmma) and rhombohedral (R-3c) structures are predicted. The hexagonal (P6/mmm) Al5W has better thermodynamic stability. The bulk modulus of the predicted Cmma and R-3c phases is close to the known P63 phase. The result demonstrates the brittle behavior of the P63 Al5W. However, the hexagonal (P6/mmm) Al5W shows lower deformation resistance in comparison to the other Al5W. Importantly, the hexagonal (P63) Al5W has the stronger degree of shear anisotropy along the (100) and (010) plane. But the orthorhombic (Cmma) Al5W has the stronger degree of shear anisotropy along the (001) plane compared to the other three Al5W. Finally, the calculated melting point follows the order of P63 > R-3c > Cmma > P6/mmm. Naturally, the Al5W shows high melting point is related to the vibration of Al atom and Al–Al bond.

Keywords

• Al5W alloy
• Structural stability
• Elastic anisotropy
• Thermodynamic properties
• First-principles calculations