Improving plasticity and toughness of Cu-Zr-Y-Al bulk metallic glasses via compositional tuning towards the CuZr

In this work, we propose a simple approach for designing plastic bulk metallic glasses (BMGs) by exploiting the ductility of intermetallic compounds involved in the BMG-forming system. Its validity was examined by investigating a series of quaternary Cu-Zr-Y-Al alloys along the composition tie-line between Cu₄₂Zr_44.4Y_3.6Al₁₀ (Y1) and the B2 CuZr phase, expressed as (Cu_0.5Zr_0.5)_x(M)_100-x (M = Zr_0.15Y_0.225Al_0.625, 84≤x≤93). When tuning the composition towards the CuZr, the glass-forming ability of alloys is dramatically degraded, showing a reduction of critical diameter D_c for BMG formation from 16 mm at x = 84 (Y1) to 2 mm at x = 93. As the composition of BMGs shifts to the CuZr terminal, the shear modulus μ of the BMGs decreases, whereas the Poisson's ratio ν increases. With respect to the Y1 BMG, compressive plasticity and toughness of the Y2 BMG (x = 92, D_c = 4 mm) with a higher concentration of the CuZr are improved, which is consistent with its lower μ and higher ν values.