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High-entropy alloys (HEAs) contain multiple principal alloying elements, but usually with simple crystal structures. Quasicrystals are structurally complex phases, but are generally dominated by only one element. However, near-equiatomic high-entropy quasicrystals have rarely been reported because they are difficult to prepare experimentally and predict theoretically. Therefore, the preparation and crystal structures of near-equiatomic high-entropy quasicrystals have drawn much interest. We report a quinary decagonal quasicrystal (DQC) with near-equiatomic alloying elements in Al20Si20Mn20Fe20Ga20 melt-spun ribbons, which is the first to our knowledge. Meanwhile, the structural features of the DQC are characterized in detail. The configurational entropy of both the alloy and DQC satisfies the entropy-based criterion for HEAs, suggesting a high-entropy DQC. Our findings provide a new strategy to develop high-entropy quasicrystals.

Seldom could metals and alloys maintain excellent properties in cryogenic condition, such as the ductility, owing to the restrained dislocation motion. However, a face-centered-cubic (FCC) CoCrFeNi high-entropy alloy (HEA) with great ductility is investigated under the cryogenic environment. The tensile strength of this alloy can reach a maximum at 1,251±10 MPa, and the strain to failure can stay at as large as 62% at the liquid helium temperature. We ascribe the high strength and ductility to the low stacking fault energy at extremely low temperatures, which facilitates the activation of deformation twinning. Moreover, the FCC→HCP (hexagonal close-packed) transition and serration lead to the sudden decline of ductility below 77 K. The dynamical modeling and analysis of serrations at 4.2 and 20 K verify the unstable state due to the FCC→HCP transition. The deformation twinning together with phase transformation at liquid helium temperature produces an adequate strain-hardening rate that sustains the stable plastic flow at high stresses, resulting in the serration feature.