High-entropy alloy (HEA) AlCrCuFeNi with equiatomic composition was prepared by arc melting. The cast material showed a two-phase structure including bcc and fcc phases. In this study, different heat treatment regimes were applied to study in detail the element distribution, microstructure changes and crystallization behavior of the alloy. Optical microscopy and scanning electron microscopy (SEM) with energy dispersive analysis were widely used for comprehensive characterization of the alloy.
The results showed the presence of a primary phase with a dendritic structure in the cast material. The sample subjected to heat treatment at 1300 °C, followed by water quenching and slow cooling in a furnace, predominantly demonstrated the formation of the Fe-Cr-rich BCC phase in the dendritic regions. The interdendritic spaces were enriched in the Al-Ni-rich B2 phase and the Cu-rich phase. The obtained data are in good agreement with the equilibrium phase predictions made using the CALPHAD method.
The Cu element plays a key role in the solidification process of the alloy in the temperature range of 900–1100 °C. This work highlights the importance of understanding the microstructure evolution and solidification behavior of high-entropy alloys, especially for their potential future applications.
High-entropy alloys (HEA) AlCrCuFeNi, due to their unique properties such as high strength, hardness and corrosion resistance, attract considerable attention in materials science. Microstructure and phase composition play a key role in determining these properties. The solidification process of HEA AlCrCuFeNi is complex and includes several stages that determine the final microstructure.
Primary crystallization usually begins with the formation of a nickel- and aluminum-rich BCC phase (body-centered cubic lattice). This phase serves as the basis for further solidification. As the temperature decreases, a redistribution of the components occurs, leading to the formation of secondary phases.
Diffusion plays an important role. The diffusion coefficients of the components in the alloy affect the growth rate of the phases and their morphology. For example, chromium and iron, which have lower diffusion mobility, can concentrate in certain areas, forming individual inclusions.
The final microstructure of AlCrCuFeNi HEA often consists of several phases: a BCC phase rich in Ni and Al, an FCC phase rich in Cu, and intermetallic compounds containing Cr and Fe. The choice of phases is determined by the component ratio, cooling rate, and thermodynamic conditions. Control of the solidification parameters allows one to control the microstructure and, therefore, the properties of AlCrCuFeNi HEA.
Author: Vikas Shivam, Shubhada Kar, GK Mandal, VC Srivastava
Institute:
Department of Materials Science, National Metallurgical Laboratory, CSIR, Jamshedpur 831007, India
Academy of Scientific and Innovation Research (AcSIR), Ghaziabad 201002, India