High-entropy alloys (HEAs) have attracted considerable attention due to their unique properties, such as high strength, wear resistance, and corrosion resistance. In particular, AlCuFeNiTi-based alloys have low density, making them promising for use in the aerospace and automotive industries. However, to expand their application, it is necessary to improve their mechanical properties.
This paper investigates the effect of changing the atomic fraction of AlNi on the microstructure and mechanical properties of AlCuFeNiTi HEA. By varying the Al and Ni content in the alloy, it is possible to influence the phase composition and structure, which in turn affects the strength and ductility of the material.
Experimental results show that increasing the atomic fraction of AlNi leads to the formation of a finer and more uniform microstructure. This is due to the fact that Al and Ni contribute to grain refinement and the formation of intermetallic phases that strengthen the alloy. In addition, changing the Al and Ni ratio can affect the formation of secondary phases such as the B2 phase, which can have a positive effect on strength and wear resistance.
In this study, three alloys, Al30Ni20Cu15Fe25Ti10 (density 6.11 g/cm3), Al25Ni25Cu20Fe25Ti05 (density 6.91 g/cm3) and Al15Ni30Cu20Fe25Ti10 (density 6.98 g/cm3), which are nonequilibrium low-density materials, were investigated. The high-entropy alloy (HEA) was designed taking into account the phase formation rules and obtained by arc melting.
Uniaxial compression test results showed that the Al30Ni20 alloy has lower ductility (approximately 3%) due to the predominance of the B2/BCC phase in the microstructure. Reducing the aluminum content leads to the formation of the fcc phase and an increase in ductility (up to approximately 9%) of the cast Al15Ni30 HEA sample. All three compositions were specially selected to achieve low alloy density in accordance with the principles of solid solution formation.
The microstructure and mechanical properties of the developed HEAs were analyzed by scanning and transmission electron microscopy, X-ray diffraction analysis, energy-dispersive X-ray spectroscopy, and indentation and uniaxial compression tests. In addition, the effect of heat treatment on the microstructure and mechanical properties of the three HEAs was investigated to determine the stability of the phases at elevated temperatures. X-ray diffraction analysis showed that the phases were stable after heat treatment at 900 ℃ for 24 hours.
The ultimate compressive strength (UCS) of the as-cast Al30Ni20, Al25Ni25, and Al15Ni30 alloys were 1824, 2008, and 2080 MPa, respectively. The compressive strain for the same specimens was 3.19, 6.64, and 9.33%. After heat treatment, the UCS of Al30Ni20-HT, Al25Ni25-HT, and Al15Ni30-HT was 1785 MPa, 2008 MPa, and 1640 MPa, and the strain increased to 3.69%, 10.22%, and 22.9%, respectively. Heat treatment revealed a relationship between strength and ductility, with an increase in ductility being accompanied by a decrease in strength. The simultaneous increase in strength and ductility with increasing aluminum content and decreasing nickel content is explained by the unique combination of a two-phase microstructure based on B2/BCC and FCC.
Mechanical property studies have shown that optimizing the atomic fraction of AlNi can significantly increase the tensile strength and hardness of AlCuFeNiTi HEAs. However, it is important to find the optimal balance to avoid excessive brittleness that can occur with too high an AlNi content.
Thus, changing the atomic fraction of AlNi is an effective way to improve the mechanical properties of high-entropy low-density AlCuFeNiTi-based alloys. Further research in this area may lead to the development of new materials with improved properties for various applications.
Author: Manoj Mugale, Mayank Garg, Ganesh Walunj, Venkata AS Kandadai, Bharat K. Jasthi, Tushar Borkar
Institute:
Department of Mechanical Engineering, Cleveland State University, Cleveland, OH 44115, USA
Department of Engineering Technology, State University at Buffalo, NY 14222, USA
Department of Materials Science and Metallurgy, South Dakota School of Mining and Technology, 501 East St. Joseph Street, Rapid City, South Dakota 57701, USA