Thermal expansion and enhanced heat transfer in high-entropy alloys

Abstract

Alloys made from equimolar mixtures of more than five elements exhibit an improved thermal diffusivity at elevated temperatures, and the improvement reaches 20% at 423 K and 50% at 573 K. This phenomenon is identified from the lengthened mean free path upon thermal expansion, and lengthening scales with lattice dilation over a wide range of temperatures.

Physical Properties of High Entropy Alloys

“…This tendency is opposite to that seen in most pure metals, but is similar to that observed in stainless steel and Inconel alloy [29,31]. The enhanced heat transfer at higher temperatures in the Al x CoCrFeNi alloys was explained by the increased phonon mean free path at higher temperature, owing to thermal expansion of the lattice [34]. Note that the electrical conductivity in the Al x CoCrFeNi alloys decreases with increasing temperature, which means that the electrical and thermal conductivities in the Al x CoCrFeNi alloys show opposite trends with respect to temperature.…”

“…Between 27 °C and 300 °C, thermal conductivity/diffusivity of these HEAs increases with increasing temperature [28,34] (see Figure 2). This tendency is opposite to that seen in most pure metals, but is similar to that observed in stainless steel and Inconel alloy [29,31].…”

“…Thermal conductivity/diffusivity has been measured in Al x CoCrFeNi and Al x CrFe 1.5 MnNi 0.5 Mo y alloys [28,34]. Table 2 compares the thermal conductivities of some Al x CoCrFeNi alloys and some representative conventional metals.…”

Charge‐Induced Disorder Controls the Thermal Conductivity of Entropy‐Stabilized Oxides

“…High‐entropy alloys (HEAs), consisting of five or more approximately equimolar compositions of elements, have proven to exhibit unique physical properties such as high hardness, thermal stability, structural stability, as well as corrosion, oxidation, and wear resistance . While microstructure and mechanical properties have been extensively studied, thermal properties, such as heat capacity and thermal conductivity, have been given far less attention . Although the random distributions of atomic configurations in HEAs are appealing for understanding the role of configurational disorder on thermal transport, insight is limited by the significant electronic contribution that arises from the metallic nature of most HEAs, which can obscure insight into the lattice thermal conductivity.…”

A new single crystal high entropy alloy with excellent high-temperature tensile property

“…Obviously, as the number of element types increases, the mixed entropy of the γ′ phase increases [35]. The high mixed entropy will give rise to severe lattice distortions and slow diffusion of elements [36,37]. Of course, the γ′ forming elements also play some roles in the solid-solution strengthening.…”