Effect of Zr and Cu on Mechanical Properties, Glass Forming Ability and Thermal Stability of Zr_63.68Cu_16.2 Ni_10.12 Al₁₀ Amorphous Alloy

The effects of Zr and Cu content on mechanical properties, glass forming ability and thermal stability of Zr_63.68−xCu_16.2+x Ni_10.12 Al₁₀ (x = 0, 0.45, 0.9, 1.35, 1.8, 2.25, 2.7) bulk metallic glasses (BMGs) has been studied. The specimens with diameters of 2, 4 and 6 mm cut from the same ladder-shaped BMG rod by copper mold suction casting method were used in the present investigation. The results show that with the increase of Cu content and the decrease of Zr content the prepared alloy specimens with diameter of 2 mm are completely amorphous. The plastic strain shows the trend of increasing at first and then decreasing. At x = 1.8, the plastic strain reaches the maximum and its value is 38.74%, about 4.3 times of Zr_63.68Cu_16.2Ni_10.12Al₁₀ (BMG) 9.10%. The elastic modulus is 51,757 MPa, the yield strength is 2079 MPa, the compressive strength and the fracture strength are 3861 MPa. With the increase of specimens size, there is obvious scale effect in plastic strain. It is also found that the plastic strain is up to 30.94% for specimens with diameter of 4 mm, showing a great plasticity. With the increase of Cu atoms and the decrease of Zr atoms, the width of the super-cooled liquid region (ΔT_x = T_x − T_g) and parameter (γ = T_x/(T_g + T_l)) both increase first and then decrease, the maximum values can reach 98 and 0.395 respectively at x = 1.35. The parameter γ tends to be constant at x = 1.8–2.7.