An Experimental Study of Thermophysical Properties for Quinary High-Entropy NiFeCoCrCu/Al Alloys

Abstract

Two quinary high-entropy alloys (HEAs) with equiatomic concentrations formed by doping either Cu or Al elements into the quaternary NiFeCoCr alloy are produced by arc melting and spray casting techniques. Their entropy of fusion, thermal expansion coefficient and thermal diffusivity are experimentally investigated with differential scanning calorimetry, dilatometry and laser flash methods. The NiFeCoCrCu HEAs contain a face-centered cubic high-entropy phase plus a minor interdendritic (Cu) phase and display a lower entropy of fusion and the Vickers hardness. The NiFeCoCrAl HEAs consist of two body-centered cubic high-entropy phases with coarse dendritic structures and show higher entropy of fusion and the Vickers hardness. Both the thermal expansion coefficient and the thermal diffusivity of the former Cu-doped alloy are significantly larger than those of the latter Al-doped alloy. Although the temperature dependence of thermal diffusivity is similar for both HEAs, it is peculiar that the thermal expansion curve of the NiFeCoCrAl alloy exhibits an inflexion at temperatures of 860–912 K.

Thermal stability and irradiation response of nanocrystalline CoCrCuFeNi high-entropy alloy

“…The theoretical density of a solid-solution alloy can be roughly estimated from the atomic fraction, atomic weight and density of each constituent element [52]. A recent experimental study of thermophysical properties has shown that the theoretical density and experimental value of a NiFeCoCrCu alloy were 8.324 and 8.295 g cm −3 [17], respectively. The value of 8.356 g cm −3 used in the simulation is the default value in SRIM.…”

“…These results indicate that, after the initial thermodynamic equilibrium is reached (∼300 s), the microstructure is driven towards a new stable state during the extended annealing to 1942 s. The melting temperature of NiFeCoCrCu HEA films can be estimated by averaging the solidus temperature and liquidus temperature of the material [90] or using the rule of mixture (ΣX i • T i m ) where X i and T i m are the molar fraction and melting temperature of the constituent element i, respectively [91]. In recent work [17], a Ni-Fe-Co-Cr-Cu fcc HEA was produced with a matrix phase formed by approximately 22 at% of Ni, Fe, Co, and Cr plus a reduced amount of ∼11% Cu together with an embedded Cu-enriched (∼67%) solid solution phase. The liquidus temperature of this alloy was determined to be 1382 °C (1655 K).…”

“…CSAs, having 3d transition elements (from Cr to Cu) with similar atomic mass and size in a fcc structure, exhibit superior tensile strength and fracture toughness at both low and high temperatures [2][3][4][5][6][7], robust phase stability [8], ultrahigh low-temperature toughness [9], superparamagnetism [10], superconductivity [11], and two orders of magnitude improvement in radiation tolerance [12]. New knowledge regarding concentrated alloys [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] has clearly revealed that compositional complexity (high chemical inhomogeneity), as opposed to the incorporation of dilute solutes [1], has a significant influence on defect dynamics that results in improved radiation performance [18][19][20][21][22].…”

Conductive property of Zr0.1Fe0.9V1.1Mo0.9O7 with low thermal expansion*

“…Meanwhile, ceramic materials have low thermal expansion coefficients but their conductivities are usually poor. Recent investigations suggest that negative thermal expansion materials could be used to prepare low thermal expansion materials by partial ion substitution, doping, or compounding with positive thermal expansion materials, [1][2][3] which could also result in high conductivity. [4][5][6][7][8] ZrV 2 O 7 is one of the isotropic negative thermal expansion materials but its negative thermal expansion is only present after a phase transition.…”