Polvo de aleación de alta entropía - HEA

What Is A High-Entropy Alloy?

High-entropy alloys (HEAs) are new materials typically composed of five or more metals in equal or near-equal proportions, exhibiting exceptional properties. The four core effects of HEAs work together to distinguish them from traditional alloys:

• High-Entropy Effect: Due to the near-equimolar mixing of multiple elements, the configurational entropy of high-entropy alloys is significantly increased, typically ≥1.5R (R is the gas constant). This high-entropy effect promotes the stability of a single solid-solution phase (such as FCC or BCC structures) while suppressing the formation of complex compounds or intermetallics. It does so by lowering the Gibbs free energy of the system (ΔG = ΔH – TΔS), enhancing the thermodynamic stability of the solid-solution phase at high temperatures.
• Lattice Distortion Effect: The differences in atomic size and chemical properties among the constituent elements in HEAs cause significant lattice distortion. This distortion enhances solid-solution strengthening, boosting the alloy’s strength and hardness, while also slowing atomic diffusion rates, which improves creep resistance and thermal stability.
• Sluggish Diffusion Effect: The complexity arising from the multi-element composition results in slower atomic diffusion rates in HEAs compared to conventional alloys. This sluggish diffusion effect delays phase separation, grain growth, and microstructural evolution, thereby enhancing stability at elevated temperatures and extending service life.
• Cocktail Effect: The synergistic interaction of multiple elements produces unexpected combinations of properties, much like blending ingredients in a cocktail to create a unique flavor. This effect allows HEAs to integrate the strengths of individual elements (e.g., strength, ductility, corrosion resistance), often surpassing the performance limits of single-element systems and exhibiting a wide range of functional characteristics.

Classified according to the number of elements and entropy value, there are also medium-entropy alloys and low-entropy alloys. Medium entropy alloys typically consist of 3-4 elements, with an entropy value ranging from 1.0R to 1.5R, offering a balance between strength and toughness. In contrast, low entropy alloys are similar to traditional alloys, typically containing 1-2 primary elements, and exhibit more homogeneous properties. The key differences are summarized as follows: