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Precipitation strengthening is an effective approach to strengthen high-entropy alloys (HEAs) with a simple face-center-cubic (FCC) structure. In this work, CoCrFeNiMo0.2 HEAs were prepared by powder metallurgy, followed by cool rolling and subsequent heat-treatment at different temperatures. The effects of cold working and annealing on microstructure and mechanical properties have been investigated. Results show the fine and dispersed (Cr, Mo)-rich σ phase with a topologically close-packed structure precipitated in the FCC matrix after the prior cold deformation process, which enhanced the mechanical property of the CoCrFeNiMo0.2 alloy. The HEA annealed at 600 °C for 48 h had a tensile strength of 1.9 GPa but an elongation which decreased to 8%. The HEA annealed at 800 °C for 12 h exhibited a tensile strength of 1.2 GPa and an elongation of 31%. These outstanding mechanical properties can be attributed to precipitation strengthening and fine-grain strengthening. [ABSTRACT FROM AUTHOR]

A novel metal matrix composite based on the NbMoCrTiAl high entropy alloy (HEA) was designed by the in-situ formation method. The microstructure, phase evolution, and compression mechanical properties at room temperature of the composite are investigated in detail. The results confirmed that the composite was primarily composed of body-centered cubic solid solution with a small amount of titanium carbides and alumina. With the presence of approximately 7.0 vol. % Al2O3 and 32.2 vol. % TiC reinforced particles, the compressive fracture strength of the composite (1542 MPa) was increased by approximately 50% compared with that of the as-cast NbMoCrTiAl HEA. In consideration of the superior oxidation resistance, the P/M NbMoCrTiAl high entropy alloy composite could be considered as a promising high temperature structural material. [ABSTRACT FROM AUTHOR]

Spherical NbMoTaW high entropy alloy (HEA) powders with a uniform particle size distribution (d 50 = 35.0 μm) were successfully prepared by using a novel industrial method combining spray drying and plasma spheroidization. The HEA powder presents an overall single body-centered-cubic structure, yet with cellular elemental segregation mainly involving Nb and W at the nanometer-scale. The microhardness of the HEA powder is 10.09 GPa, about 50% higher than that of the HEA with the same composition in bulk state. This ultra-high microhardness endows the HEA powder with potential for application as superhard materials. In addition, the new preparation method of spherical refractory HEAs powder also would be of great significance for the future development of refractory HEAs (or complex refractory alloys) towards industrial applications, especially those based on 3D printing and thermal coatings. Image 1 • Pherical NbMoTaW high entropy alloy powders can be prepared by combining spray drying and plasma spheroidization. • The HEA prealloyed powders have smooth surface, dense interior and uniform chemical composition. • The microhardness of the HEA powder is 10.09 GPa, about 50% higher than that of the NbMoTaW HEA in bulk state. [ABSTRACT FROM AUTHOR]