Micro/nanomechanical characterization of a decagonal single-grain quasicrystal, Al74.7Co16.9Ni8.4, has been carried out. Hardness and elastic modulus were measured by nanoindentation using a nanoindenter. Fracture toughness was measured by microindentation using a microindenter. It was found that the Al74.7Co16.9Ni8.4 quasicrystal shows a high hardness of 11.4 GPa and an elastic modulus of 177 GPa but a low fracture toughness of 0.81 MPa m1/2. Nanoindentation resulted in a pile-up around the indent. A small hysteresis was found in the multiple indentation of the quasicrystal. Indentation deformation, creep and fracture mechanisms were discussed in conjunction with the destruction of the quasicrystalline structure and the formation of the crystalline structure in indentation.
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