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The AlCoCrFeNi 2.1 eutectic high-entropy alloy (EHEA) has become one of the hottest research topics owing to its comprehensive mechanical properties. In this study, the AlCoCrFeNi 2.1 EHEA was fabricated via the laser powder bed fusion (L-PBF) technique, and the grain morphology, eutectic structure, mechanical properties, and deformation mechanism were investigated. The results indicate that the samples have superfine grains and nano-lamellar eutectic structures, attributable to the high cooling rate of the L-PBF process. Furthermore, the phenomenon of solute trapping was observed in the boundary of the FCC and B2 semi-cohesive phase in the nano-lamellar eutectic structure. Based on the special eutectic structure of the AlCoCrFeNi 2.1 EHEA prepared using the L-PBF technique, the samples exhibited an exceptional tensile strength of up to 1.6 GPa, accompanied by tensile ductility of over 9.5 %. The improvement of mechanical properties may be attributable to the Hall–Petch strengthening and back stress effect caused by refining the eutectic structure, whereas the growth of the nano-lamellar structure may be closely related to the solute-trapping effect. • Nano-lamellar EHEA with K–S type OR was prepared by additive manufacturing. • The L-PBF EHEA exhibited an exceptional tensile strength of up to 1.6 GPa. • The solute trapping phenomenon was observed at the boundary of nano-lamellar. [ABSTRACT FROM AUTHOR]

Solid-solution agglomerated ZrO 2 -based powders co-doped with Gd 2 O 3 , Yb 2 O 3 and Y 2 O 3 rare earth oxides were synthesized by solid-phase sintering and spray drying. The corresponding GYYZO coating was prepared by using atmospheric plasma spraying, while the 8YSZ coating was also prepared as a control group for the high temperature performance investigation. The high temperature structure and phase stability as well as the sintering resistance of both coatings were investigated by SEM, XRD, DSC, EPMA and TEM observations. The results showed that the 8YSZ coating began to undergo a phase transition of tetragonal (t) phase to monoclinic (m) after 50 h heat treatment at 1400 °C, while the GYYZO coating remained free of phase transition even heat-treated for up to 200 h, demonstrating a better phase stability. In addition, as an indicator of sintering resistance of the coating, the porosity of the 8YSZ coating decreased up to 90.1 % after 200 h heat treatment, while that of the GYYZO coating decreased only 20.6 %. The superior high temperature performance of GYYZO coating can be explained by the pinning effect of nano-pores on grain boundaries. The formation of nano-pores was associated with the evolution of defect clusters in the coating, which were facilitated by the substitution defects and oxygen vacancies created by the Gd Yb co-doping. During the heating process, these clusters migrated along with the grain boundaries and formed pearl-string-like nano-pores at the grain boundaries. The eventual formation of nanopores not only further inhibits grain boundary migration to reduce sintering, but also prevents the segregation of Y elements to hinder t-phase to m-phase transition. • GYYZO coating has excellent phase stability and sintering resistance at high temperature. • The nanopores of GYYZO coating have pinning effect on grain boundaries. • The pinning effect of nanopores can inhibit grain boundaries migration and Y elements segregation. [ABSTRACT FROM AUTHOR]

Homemade nano-agglomerated powders 8YSZ powders for PS-PVD were prepared by the spray drying, then calcination processes at four different temperatures (500 °C, 700 °C, 900 °C and 1100 °C) were carried out on the spray-dried powders. Checked by laser particle sizer, scanning electron microscope (SEM) and X-ray diffraction (XRD), the physical properties, microstructure and phase constitutions of the calcined powders were investigated. The results show that the size of powders calcined at 500 °C is increased relative to the spray-dried powder, whereas the powders calcined at 700 °C, 900 °C and 1100 °C possess smaller size. The binding force of the primary particles tend to rise with the increase of calcination temperature. When the temperature was up to 900 °C and above, it was found that the sintering neck indicating with strong binding was formed between the primary particles. In parallel, the powders underwent an m-ZrO 2 to t-ZrO 2 transition as the calcination temperature rose. It is also found that the PS-PVD prepared coatings which were obtained by using the above powders undergo a transformation from a feather-like to a dense laminate structure as the calcination temperature rises. It is noteworthy that the coating obtained by the powders calcined at 700 °C have a special three-layer composite structure of near dense surface layer, columnar intermediate layer and dense sub-layer. The composite structural coating has excellent adhesion and thermal shock resistance, with a bonding strength of 81MPa and no major spalling when water quenched 100 cycles at 1100 °C. [ABSTRACT FROM AUTHOR]