Abstract
The phase stability and elastic properties of paramagnetic (PM), ferromagnetic (FM) and antiferromagnetic (AFM) phases in L12-(Ni,Cu)3(Al,Fe,Cr) alloy are first investigated using the exact muffin-tin orbitals (EMTO) method in combination with the coherent potential approximation (CPA). The result shows the AFM structure phase of the three is the most stable in the ground state. Calculated elastic constants show that all the phases are mechanically stable, and have uncovered that L12-(Ni,Cu)3(Al,Fe,Cr) can achieve good strength and ductility simultaneously. Then, crucial thermal properties are described satisfactorily using the Debye–Grüneisen model, showing heat capacity, Gibbs free energy G, the competitive contribution of entropy −TS and enthalpy H exhibiting significant temperature dependences. Moreover, the magnetic phase transition thermodynamics was studied, which suggests that −TS has a primary contribution to Gibbs free energy and may play a key role in the phase transition. The present results can benefit the understanding of the mechanical, thermodynamic and magnetic properties of the L12 structure phase in 3d high-entropy alloys.
Highlights
High-entropy alloys (HEAs), near-equiatomic solid solutions of five or more elements, represent a new strategy for the design of materials with properties superior to those of conventional alloys. [1,2].With multiple principal components, they inherently possess unique microstructures and many impressive properties, such as high strength and hardness, excellent magnetic property, thermal stability, wear-resistance and corrosion resistance [3,4,5]
These favorable properties seem to originate from the γ0 precipitates uniformly distributed within a disordered face-centered cubic (FCC) solid solution matrix of HEAs, mimicking typical γ + γ0 microstructures observed in the case of many Ni-super alloy and forms the basis
In order to investigate magnetic phase transition of the L12 -(Ni,Cu)3 (Al,Fe,Cr), the Gibbs free energy G as a function of temperature at constant pressures was calculated by the equation G = H − TS, and the two components of enthalpy H and entropy contribution −TS were studied, which are shown in Figures 3 and 4
Summary
High-entropy alloys (HEAs), near-equiatomic solid solutions of five or more elements, represent a new strategy for the design of materials with properties superior to those of conventional alloys. [1,2]. L21 structures are observed in HEAs through X-ray diffraction (XRD) and transmission electron microscopes (TEM) measurements [8,9,10] These phases are beneficial to the mechanical behavior of HEAs. For instance, the ordered L12 -(Ni,Cu) (Al,Fe,Cr) phase (γ0 phase), which has been obtained by annealing of Al0.3 CuCrFeNi2 at 550–700 ◦ C, could improve the mechanical strength, grain refinement, microstructures and coarsening behavior of HEAs [8]. The ordered L12 -(Ni,Cu) (Al,Fe,Cr) phase (γ0 phase), which has been obtained by annealing of Al0.3 CuCrFeNi2 at 550–700 ◦ C, could improve the mechanical strength, grain refinement, microstructures and coarsening behavior of HEAs [8] These favorable properties seem to originate from the γ0 precipitates uniformly distributed within a disordered FCC solid solution matrix of HEAs, mimicking typical γ + γ0 microstructures observed in the case of many Ni-super alloy and forms the basis. Magnetic phase transition is predicted by Gibbs free energy G and the competitive contribution of entropy −TS and enthalpy H, simultaneously
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