Rotating-beam fatigue properties and effect of Ni element additive in bulk glassy Zr₅₀Cu₄₀Al₁₀ alloys

We examined Wöhler curves of Zr₅₀Cu₄₀Al₁₀ and Zr₅₀Cu₃₀Ni₁₀Al₁₀ bulk glassy alloys using a rotating-beam fatigue test to evaluate the effect of adding a Ni element on fatigue strength. As a result, we found that the fatigue limit was increased from 250 MPa to 500 MPa by adding 10 at% Ni instead of Cu to a Zr₅₀Cu₄₀Al₁₀ bulk glassy alloy. A Zr₅₀Cu₄₀Al₁₀ bulk glassy alloy exhibits a wide fatigue-fractured region with striation-like marks up to 80% in response to low applied stress (near the fatigue limit). However, adding Ni limits the fatigue-fractured region to half of the whole fractured surface. We also observed fatigue-fracture surfaces of Zr₅₀Cu₄₀Al₁₀ and Zr₅₀Cu₃₀Ni₁₀Al₁₀ bulk glassy alloys to estimate the fatigue-fracture toughness. The fatigue fracture toughness decreases suddenly around N = 10³ to 10⁴, similar to Wöhler curves.