Improving the glass forming ability and plasticity of ZrCuNiAlTi metallic glass by substituting Zr with Sc

Abstract

The present study reports the effect of substituting Zr with Sc on the glass forming ability (GFA) and mechanical properties of ZrCuNiAlTi bulk metallic glass (BMG). Results showed that Zr 57- x Cu 20 Ni 8 Al 10 Ti 5 Sc x ( x = 0, 1, 2, 3, 4 at%) BMGs had the best GFA at x = 2, and the critical size was 10 mm, which correlated well with the GFA indicator ( T rg and γ ). The large atomic radius of Sc and small Gibbs free energy difference between the supercooled liquid and crystalline solid (Δ G l-c ) caused significant atomic size mismatch and inhibited crystallization during cooling, ultimately improving GFA. Compression test results indicated that the plasticity of the Zr 55 Cu 20 Ni 8 Al 10 Ti 5 Sc 2 BMG increased fivefold (9.1%) relative to that of the Sc-free case, whereas fracture stress was successfully retained at a value of 1815 MPa. The high plastic strain of Zr 55 Cu 20 Ni 8 Al 10 Ti 5 Sc 2 BMG can be attributed to the localized nanocrystallization phenomenon under uniaxial compression and to the high relaxed excess free volume (REFV) in ZrCuNiAlTiSc BMGs. The high REFV prevented the expansion of shear bands, generated secondary shear bands, and finally increased plasticity. • GFA and plasticity are both enhanced by substituting with Sc in ZrCuNiAlTi BMGs. • The smaller ΔGl-c of Sc2 compared with Sc-free BMG results in its high GFA. • Nanocrystalline phenomenon is the main reason for the high plasticity of Sc2 BMG. • The high plasticity of Sc2 alloy is also attributed to its higher REFV than others.