Futuristic high entropy alloy lattice structure created by selective laser melting.

Unlocking the Secrets of High Entropy Alloys: A Revolutionary Material for the Future

Lena Voss in Tech & Innovation September 2025 • 5 min read.

"Discover how selective laser melting is transforming the AlCoCrFeNi alloy, paving the way for stronger, more durable materials in aerospace, biomedicine, and beyond."

The quest for new materials is central to advancing technology and ensuring the sustainable use of Earth's resources. Traditional alloys, often based on one or two primary elements, have limitations in terms of performance and adaptability. High entropy alloys (HEAs) represent a paradigm shift in material science, offering unprecedented design flexibility and superior properties.

High entropy alloys, defined as alloys containing five or more elements in significant concentrations, defy conventional alloy design principles. Instead of relying on a single dominant element, HEAs harness the synergistic effects of multiple elements to create unique microstructures and exceptional performance characteristics. Among these, the quinary HEA composed of aluminum, cobalt, chromium, iron, and nickel (AlCoCrFeNi) has garnered significant attention due to its remarkable corrosion resistance, high hardness, and strength, even at elevated temperatures.

While conventional methods like casting and plastic deformation are used to produce HEAs, these techniques often struggle to create complex shapes and fine-grained structures. Additive manufacturing (AM), particularly selective laser melting (SLM), has emerged as a promising alternative for HEA fabrication. SLM's layer-by-layer control enables the creation of intricate geometries and the manipulation of microstructure, opening new possibilities for HEA applications.

How Does Selective Laser Melting (SLM) Enhance Alloy Properties?

Futuristic high entropy alloy lattice structure created by selective laser melting.

Selective laser melting (SLM) is a cutting-edge additive manufacturing technique that utilizes a focused laser beam to selectively melt and fuse powder materials layer by layer, creating three-dimensional objects with intricate geometries and tailored properties. This method is particularly advantageous for producing high entropy alloys (HEAs) due to its ability to achieve rapid solidification rates and precise control over the alloy's microstructure. SLM's layer-by-layer approach allows for the creation of complex shapes that are difficult or impossible to manufacture using traditional methods like casting or forging.

The SLM process begins with a fine layer of powder material spread evenly across a substrate. A high-powered laser then scans the powder bed, selectively melting and fusing the particles according to a pre-designed pattern. Once a layer is complete, the build platform lowers, and a new layer of powder is applied. This process repeats until the entire object is built, layer by layer. The key to SLM's effectiveness lies in its ability to create rapid heating and cooling cycles, which result in unique microstructures and enhanced material properties.

Densification: SLM enables the production of HEAs with high densities by carefully controlling volumetric energy density (VED).
Phase Control: SLM can create non-equilibrium phases, such as body-centered cubic (BCC) structures, which differ from those obtained through traditional methods.
Microstructure Refinement: The rapid cooling rates in SLM lead to ultra-fine grain structures, enhancing the alloy's strength and hardness.
Texture Manipulation: SLM allows for the control of crystallographic texture, influencing the alloy's mechanical properties and performance.

The study highlights that the density of the SLM-processed AlCoCrFeNi alloy increases with the volumetric energy density (VED), reaching a maximum relative density of 98.4%. This improvement is attributed to the high temperature achieved with increased VED, which reduces weld pool tension and enhances flowability. The elevated temperature also facilitates liquid phase diffusion, improving interlayer bonding and overall densification. In addition to enhancing density, SLM manipulates the alloy's phase composition. Unlike conventional methods that typically yield a mix of face-centered cubic (FCC) and BCC phases, SLM favors the formation of BCC phases, specifically disordered A2 and ordered B2 structures. The content of the B2 phase increases with higher VED, indicating that SLM promotes the formation of this ordered structure. Interestingly, the process also leads to the precipitation of Fe-Cr phases, which are not typically observed in cast HEAs, suggesting unique thermodynamic conditions during SLM.

The Future of High Entropy Alloys

The research demonstrates that selective laser melting is a viable and effective method for producing high-density, high-performance AlCoCrFeNi high entropy alloys. By carefully controlling the SLM process parameters, it is possible to manipulate the alloy's microstructure, phase composition, and texture to achieve desired properties. The enhanced micro-hardness, corrosion resistance, and unique phase formations make SLM-processed HEAs promising candidates for various applications, including aerospace, biomedicine, and energy. The ability to tailor material properties through SLM opens up new avenues for designing advanced materials with enhanced performance and functionality, paving the way for innovations across multiple industries.

About this Article -

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This article is based on research published under:

DOI-LINK: 10.1016/j.intermet.2018.10.018, Alternate LINK

Title: Microstructures And Properties Of An Equimolar Alcocrfeni High Entropy Alloy Printed By Selective Laser Melting

Subject: Materials Chemistry

Journal: Intermetallics

Publisher: Elsevier BV

Authors: P.D. Niu, R.D. Li, T.C. Yuan, S.Y. Zhu, C. Chen, M.B. Wang, L. Huang

Published: 2019-01-01

Everything You Need To Know

How does selective laser melting affect the density, phase and microstructure of high entropy alloys?

Selective laser melting (SLM) enhances alloy properties through several key mechanisms. It enables the production of high-density high entropy alloys (HEAs) by carefully controlling volumetric energy density (VED). SLM also allows for phase control, creating non-equilibrium phases like body-centered cubic (BCC) structures, and refines the microstructure, leading to ultra-fine grain structures that enhance the alloy's strength and hardness. Furthermore, SLM permits texture manipulation, influencing the alloy's mechanical properties. Traditional methods lack this level of precision, and often result in a mix of face-centered cubic (FCC) and BCC phases.

What exactly defines a 'high entropy alloy,' and what makes them different from traditional alloys?

High entropy alloys (HEAs) are defined as alloys containing five or more elements in significant concentrations. Unlike traditional alloys, which rely on one or two primary elements, HEAs harness the synergistic effects of multiple elements to create unique microstructures and exceptional performance characteristics. For example, the AlCoCrFeNi alloy consists of aluminum, cobalt, chromium, iron, and nickel, giving it remarkable corrosion resistance and high hardness, even at elevated temperatures. While the definition is broad, the specific combination and processing method greatly influence the resultant properties.

In what ways does selective laser melting (SLM) specifically manipulate the phase composition of the AlCoCrFeNi alloy?

Selective laser melting (SLM) manipulates the AlCoCrFeNi alloy's phase composition by favoring the formation of body-centered cubic (BCC) phases, specifically disordered A2 and ordered B2 structures. The content of the B2 phase increases with higher volumetric energy density (VED), indicating that SLM promotes the formation of this ordered structure. The process also leads to the precipitation of Fe-Cr phases, which are not typically observed in cast HEAs, suggesting unique thermodynamic conditions during SLM. This level of control is generally not achievable through conventional methods like casting.

What are the potential future applications of high entropy alloys made with selective laser melting (SLM)?

High entropy alloys produced using selective laser melting (SLM) hold significant promise for various applications due to their enhanced micro-hardness, corrosion resistance, and unique phase formations. These alloys are promising candidates for aerospace applications, where high strength-to-weight ratios and resistance to extreme conditions are critical. They are also valuable in biomedicine for their biocompatibility and corrosion resistance, as well as in energy applications due to their thermal stability and mechanical properties at high temperatures. The ability to tailor material properties through SLM opens up new avenues for designing advanced materials with enhanced performance and functionality, thus paving the way for innovations across multiple industries.

What is the role of volumetric energy density in the selective laser melting (SLM) process, and how does it affect the resulting alloy's properties?

Volumetric energy density (VED) plays a crucial role in selective laser melting (SLM) as it directly impacts the density of the SLM-processed AlCoCrFeNi alloy. As VED increases, the density of the alloy also increases, reaching a maximum relative density of 98.4%. This improvement is attributed to the high temperature achieved with increased VED, which reduces weld pool tension and enhances flowability. The elevated temperature also facilitates liquid phase diffusion, improving interlayer bonding and overall densification. Therefore, controlling VED is essential for achieving optimal material properties in SLM-processed HEAs. In contrast, processes like casting do not offer the same degree of control over energy density.