Owing to novel design concepts and their unique properties, high-entropy alloy (HEA) has become a hot topic in material science. At present, the studies and applications of high-entropy alloy are still mainly limited to the preparation and synthesis of materials. With its wide application in industry, it must involve the research of high-entropy alloy in welding field. This paper describes the welding of high-entropy alloy with the same material, welding between high-entropy alloy and dissimilar material, and welding between dissimilar material with high-entropy alloy as filler material. The paper focuses on analyzing the welding method, high entropy alloy components, the initial state of welding and welding parameters, and other factors on the joint organization and properties. While the high-entropy alloy is mainly applied as filler material, the high entropy effect and hysteresis diffusion effect for interface controlling are particularly important. Finally, the high-entropy alloy coatings under different preparation methods are analyzed in detail, introducing the cladding process, the addition of microelements, the effect of post-heat treatment, and comparing the wear resistance high-entropy alloy coatings under the laser melting process. By summarizing the research and application of high-entropy alloy in the welding field, it is pointed out that the current problems are that the corresponding standard between high-entropy alloy system and welding process has not been established and the formation mechanism of defects has not been clarified. The future research directions of high entropy alloy in welding field are proposed.

High entropy alloy is defined as an alloy containing four or more main elements. The atomic fraction of the main elements is greater than 5% and not more than 35%, which has excellent properties such as high strength, high wear resistance and high corrosion resistance. Refractory high-entropy alloy is a new type of superalloy designed and developed based on high-entropy alloy of refractory elements, which has broad application prospects in aerospace, petrochemical and other fields, and is expected to replace traditional superalloys. This paper reviews the composition design of refractory high-entropy alloys from the aspects of element selection and addition of trace elements, and its phase composition has single-phase structure and duplex structure, and the preparation method and performance characteristics of refractory high-entropy alloys are studied, and finally gives the problems and challenges faced by refractory high entropy alloys. This review provides a valuable reference for researchers in the component design, microstructure regulation and performance development of refractory high entropy alloys.

With the development of aerospace technology, protective materials for hot-end components have reached higher requirements. In this paper, a （Zr_xY_（1-x/4）Ta_（1-x/4）Ti_（1-x/4）Er_（1-x/4））O（x=0.2, 0.544, 0.672, 0.796和0.92）quintuple element ceramic system composite is studied based on the solid-phase reaction method and molecular dynamics simulation. By experimental means, ZrO₂ （99.99%）, Y₂O₃ （99.99%）, Ta₂O₅ （99.99%）, Er₂O₃ （99.99%） and TiO₂ （99%） powder was used as raw material to prepare （Zr_xY_（1-x/4）Ta_（1-x/4）Ti_（1-x/4）Er_（1-x/4））O composite by the solid-phase reaction method. The thermal conductivity of （Zr_xY_（1-x/4）Ta_（1-x/4）Ti_（1-x/4）Er_（1-x/4））O ceramic material was investigated computationally using the LAMMPS program. The study result shows that a consistent trend in the variation of the thermal conductivity is obtained by experiments and simulations at the interval of 200-900 °C. The thermal conductivity reaches a minimum value at x = 0.796, which proves the feasibility of molecular dynamics simulation of the thermal conductivity of multi-ceramic materials. Meanwhile, the effect of porosity on thermal conductivity was investigated, and it is found that there was a competitive relationship between the elemental ratios and the effect of porosity on thermal conductivity. When the porosity is larger than 6.67%, the effect of the porosity is the main influencing factor. when the porosity is smaller than 6.67%, the elemental ratios are the dominant factors in the thermal conductivity.

A micro-diffusion phase-field model based on the atom occupancy probability of single lattice point was presented to describe the phase transition process, the heterogeneous interface structure and composition evolution of Ni₅₉Al₂₂V₁₉ medium entropy alloy during phase transformation at atomic scale. It is found that in the early stage of Ni₅₉Al₂₂V₁₉ medium entropy alloy precipitation, L1₂ and a small amount of ordered phase of DO₂₂ and L1₀ are precipitated. As the aging process goes on, the coexistence of L1₂ and DO₂₂ is formed in the aging process and four kinds of heterogeneous interfacial structures are found. At the initial phase of phase transformation, interfacial structures of A play a dominant role. With the growth and decomposition of the ordered phase, the number of interfacial structures of A decreases while the number of interfacial structures of D increases; in the Ni₅₉Al₂₂V₁₉ medium entropy alloy the ordered domain boundaries provide Al atoms for the growth of L1₂ during the precipitation process until the alloy reaches equilibrium. During the precipitation process, the precipitation mechanism of γ′ phase is compositional ordering and instable decomposition mechanism, and the precipitaion mechanism of phase θ is instable; the interaction potential between Ni-Al first neighbor atoms increases with the increase of the long program parameters and is proportional to the temperature, the incubation period of medium entropy alloy in Ni₅₉Al₂₂V₁₉ becomes longer with the increase of temperature.