Ductile quasicrystalline alloys

An icosahedral (I) quasicrystalline phase with a grain size below 40 nm was formed as a metastable phase in crystallization of the bulk glassy Zr₆₅Al_7.5CU_17.5-xNi₁₀M_x (M=Ag, Pd, Au, or Pt; x=5 and 10 at %) alloys. The volume fraction (V_f) of the I phase is about 85% for the 5% M alloy and nearly 100% for the 10% M alloy. The I phase changes to Zr₂Cu+Zr₂Ni+ Zr₂Al₃ in a fully annealed state. Compressive fracture strength (σ_c,f) and fracture elongation (∈ε_c,f) of the 10% Pd cylinder with a diameter of 2 mm are respectively 1640 MPa and 2.2% for the glassy phase and increase to 1830 MPa and 3.1% for the I phase. The increase in σ_c,f is due to the suppression effect of the I particles against the shear deformation of the intergranular glassy phase, and the increase in ε_c,f results from the localization effect of deformation into the glassy layer. The precipitation of the I phase implies that the glassy alloys include randomly oriented I configurations. The present work shows promise for the new class of high-strength nanoquasicrystalline materials.