A Highly Fatigue-Resistant Zr-Based Bulk Metallic Glass

The strength-normalized fatigue endurance strength of the bulk metallic glass (BMG) Zr_52.5Cu_17.9Ni_14.6Al₁₀Ti₅ (Vitreloy 105) has been reported to be the highest for any BMG; however, to date, there has been no explanation of why this material is so much better than other Zr-based compositions. In this study, the fatigue-crack growth behavior of Zr_52.5Cu_17.9Ni_14.6Al₁₀Ti₅ was compared in ambient air vs dry nitrogen environment. The excellent fatigue life behavior is attributed to a relatively high fatigue threshold (ΔK _TH ≈ 2 MPa√m) and a lack of sensitivity to environmental effects on fatigue-crack growth in ambient air, as compared to other Zr-based BMGs. Fatigue life experiments conducted in ambient air confirmed the excellent fatigue life properties with a 10⁷-cycle endurance strength of ~0.24 of the ultimate tensile strength; however, it was also found that casting porosity, even in limited amounts, could reduce this endurance strength by as much as ~60 pct. Overall, the BMG Zr_52.5Cu_17.9Ni_14.6Al₁₀Ti₅ appears to have excellent strength and fatigue properties and should be considered as a prime candidate material for future applications where good mechanical fatigue resistance is required.