High-entropy alloy coatings (HEAC) exhibit good frictional wear and corrosion resistances, which are of importance for structure materials. In this study, the microstructure, surface morphology, hardness, frictional wear and corrosion resistance of an AlCoCrFeNi high-entropy alloy coating synthesized by atmospheric plasma spraying (APS) were investigated. The frictional wear and corrosion resistance of the coating are simultaneously improved with an increase of the power of APS. The influence of the APS process on the microstructure and mechanical behavior is elucidated. The mechanisms of frictional wear and corrosion behavior of the AlCoCrFeNi HEAC are discussed in detail.

The high-entropy alloy coatings reinforced with nano oxides were synthesized by the atmospheric plasma spraying (APS). The crystal structure, microstructure, surface morphology, hardness and wear resistance properties of the CoCrFeNiAl and CoCrFeNiMo high-entropy alloy coatings are investigated. For CoCrFeNiAl high entropy coating (HEC) not only has high hardness (573 ± 19 Hv_0.1) but also has good wear resistance [The coefficients of friction (COF) is 0.49 ± 0.04]. The transition of the wear mechanism obviously appears between the two HECs. The influences of the structure, composition and hardness on the tribological behavior of high-entropy alloy coatings were discussed in details. GRAPHICAL ABSTRACT IMPACT STATEMENT Nano oxides enhanced high-entropy coatings (HECs) are successfully fabricated by atmospheric plasma spraying, which exhibit the highest hardness and the best wear resistance in HECs and high-entropy alloys.

Al₂O₃ nanoparticle-reinforced Al-12Si matrix composites were successfully fabricated by hot pressing and subsequent hot extrusion. The influence of weight fraction of Al₂O₃ particles on the microstructure, mechanical properties, and the corresponding strengthening mechanisms were investigated in detail. The Al₂O₃ particles are uniformly distributed in the matrix, when 2 and 5 wt. % of Al₂O₃ particles were added to the Al-12Si matrix. Significant agglomeration can be found in composites with 10 wt. % addition of Al₂O₃ nanoparticles. The maximum hardness, the yield strength, and tensile strength were obtained for the composite with 5 wt. % Al₂O₃ addition, which showed an increase of about ~11%, 23%, and 26%, respectively, compared with the Al-12Si matrix. Meanwhile, the elongation increased to about ~30%. The contribution of different mechanisms including Orowan strengthening, thermal mismatch strengthening, and load transfer strengthening were analyzed. It was shown that the thermal mismatch strengthening has a more significant contribution to strengthening these composites than the Orowan and load transfer strengthening mechanisms.

To explore a novel high strength and low modulus ultralight-weight complex concentrated alloys (ULW-CCAs), a series of light alloys are designed and explored based on some low-density and low modulus elements, such as Al, Li, Mg, Ca, Si, and Y. An Al_19.9Li₃₀Mg₃₅Si₁₀Ca₅Y_0.1 (at %) CCA with a high specific strength of 327 KPa·m⁻³ is successfully developed. After adjusting the composition, the Al₁₅Li₃₅Mg₄₈Ca₁Si₁ CCA with the good compressive plasticity is successfully developed. The Al₁₅Li₃₈Mg₄₅Ca_0.5Si_1.5 and Al₁₅Li₃₉Mg₄₅Ca_0.5Si_0.5 CCAs exhibit good plasticity of >45%, and >60%, respectively. These ULW-CCAs show the high specific strength, good ductility, and low Young’s modulus, as compared with the previously reported CCAs.