The preparation of medium- and high-entropy alloys are said to present certain difficulties, including densification, cracks and residual stress, dimensional accuracy and surface polish, chemical homogeneity, crystallization and microstructure control, property anisotropy, etc. As a result, more research should be done to use additive manufacturing techniques to better understand this new family of metallic materials.
Due to their distinct and superior features, high-entropy alloys, a novel class of multi-component complex alloy materials, have garnered considerable interest. High-entropy materials are prepared similarly to conventional materials, but they also have unique characteristics when compared to conventional alloys.
Three-dimensional bulk materials, two-dimensional film and sheet materials, one-dimensional fiber materials, and zero-dimensional powder materials are the primary types of high-entropy materials that are prepared and formed starting from different dimensions. Arc melting, induction melting, additive manufacturing, powder metallurgy, magnetron sputtering, laser cladding, and other preparation technologies are the principal ones. The deformation processing technique is also used to prepare high-entropy thin plates, wires, and fibers.
The traditional smelting method will unavoidably result in a temperature gradient during the cooling of the alloy block, which will lead to the microstructure becoming uneven, resulting in the typical heterogeneous casting structure with fine grain areas on the surface, columnar grain areas in the middle, and coarse columnar grain areas inside. One of the main problems affecting material qualities is casting flaws, such as voids and cracks produced during the smelting process. To obtain a homogeneous structure or remove casting flaws from the initial product, further deformation and heat treatment are frequently necessary. Compared with the traditional smelting technology, the additive manufacturing technology of selective melting has a higher cooling rate, and the prepared alloy has a uniform structure and fine grain, showing excellent comprehensive mechanical properties. More and more work applies additive manufacturing technology to the preparation and performance improvement of high-entropy alloys.
The following list of benefits of additive manufacturing technology can be summed up:
It is simple to obtain uniform and fine grains, even nano or micro grains because the heat is uniform, the heat-affected zone is small, and the heat is quickly cooled. The forming precision is also high, allowing the size and shape of the alloy to be precisely controlled, and the processing cycle can be effectively shortened. The current manufacture of large-sized alloys still faces many difficulties, and a major component in advancing additive manufacturing technology is the maturation of high-entropy alloy powder preparation technology.
Summarize
High-entropy alloys, a growing complex multi-principal alloy, primarily concentrate on a new region in the phase diagram's core; their distinctive design principles and superior physical and chemical properties have produced a large number of novel high-entropy alloys with exceptional properties. In the areas of structural materials, functional materials, and healthcare, entropic materials have demonstrated significant development potential.
After more than ten years of development, from the first alloy block through high-entropy materials of various dimensions and scales, including films, coatings, strips, sheets, wires, and powders, the definition and material system of high-entropy alloys have experienced a steady improvement.
Although there have been numerous advances in high-entropy materials, the composition design, sample preparation, and performance mechanism analysis of the alloy are more challenging because of the alloy's inherent complexity. Future research on high-entropy alloys must not only be "performance-driven," but also "process-driven" in order to create novel high-entropy materials that are suitable for unique processes including deformation, casting, powder production, and powder smelting. It is of great significance to the further development of high-entropy alloys and the expansion of application fields.