Tailoring the physical properties of Ni-based single-phase equiatomic alloys by modifying the chemical complexity

Abstract

Equiatomic alloys (e.g. high entropy alloys) have recently attracted considerable interest due to their exceptional properties, which might be closely related to their extreme disorder induced by the chemical complexity. In order to understand the effects of chemical complexity on their fundamental physical properties, a family of (eight) Ni-based, face-center-cubic (FCC), equiatomic alloys, extending from elemental Ni to quinary high entropy alloys, has been synthesized, and their electrical, thermal, and magnetic properties are systematically investigated in the range of 4–300 K by combining experiments with ab initio Korring-Kohn-Rostoker coherent-potential-approximation (KKR-CPA) calculations. The scattering of electrons is significantly increased due to the chemical (especially magnetic) disorder. It has weak correlation with the number of elements but strongly depends on the type of elements. Thermal conductivities of the alloys are largely lower than pure metals, primarily because the high electrical resistivity suppresses the electronic thermal conductivity. The temperature dependence of the electrical and thermal transport properties is further discussed, and the magnetization of five alloys containing three or more elements is measured in magnetic fields up to 4 T.

Local Structure and Short-Range Order in a NiCoCr Solid Solution Alloy

“…Previous experiments have found that Cr is a specific element in these solid solution alloys that has a critical effect on the mechanical and physical properties [12,21]. Besides the exceptional damage-tolerance at low temperature, the electrical and thermal conductivity decreased nearly one-order of magnitude for NiCoCr compared with those of NiCo [12].…”

“…Besides the exceptional damage-tolerance at low temperature, the electrical and thermal conductivity decreased nearly one-order of magnitude for NiCoCr compared with those of NiCo [12]. Due to the multi-principle-element in the fcc structure, a complex local structure is expected in HEAs which may play an important role to the abnormal mechanical and physical properties of these solid solution alloys.…”

“…In the stainless-steel alloys of FeNiCr with different compositions, previous thermal diffuse neutron scattering measurements have revealed [37,38] that Cr has a strong tendency to bond with Ni forming short-range order. Ni-based multicomponent solid solution alloys have been studied broadly in recent years, and experimental investigations have found that Cr-incorporation in the fcc lattice plays a key role for their physical properties [12]. Generally, both electrical and thermal conductivities decrease with the increase of atomic species in the alloys.…”

“…As a new class of materials, these compositionally complex alloys have attracted a large number of research interests over the past decade, leading to the discovery of some excellent mechanical properties and interesting physical properties [3][4][5][6][7][8][9][10]. Recently, many multicomponent solid solution alloys with 3d transition elements from Cr to Ni in the periodic table, which have similar atomic size, have been synthesized and all of these Ni-based alloys have a simple face-centered cubic (fcc) structure [10][11][12][13][14]. Some of these HEAs exhibit high strength and excellent wear resistance at low and high temperatures, which makes them attractive for industrial applications.…”

“…The single phase polycrystal and single crystal samples used for the measurements were synthesized in equal atomic composition from high purity elements (>99.9 pure) by arc melting, casting, zone melting and thermal treatments [12,16]. The samples were cut into thin disks (~1 mm of thickness for single crystals and ~150 µm for polycrystals) by electrical discharge machining and electrochemically polished.…”