Fatigue damage in bulk metallic glass II: Experiments

Cyclic fatigue was investigated in metallic glasses using fracture mechanics-based crack-growth and stress-life experiments. Steady-state crack growth in a Zr-based bulk metallic glass occurred with a Paris law exponent of ∼1.5. Growing planar fatigue cracks were often noted to destabilize into a wavy crack front geometry, and the conditions determining the stability of these cracks are analyzed. Transient crack-growth rates were measured during variable-amplitude fatigue. Stress-life experiments showed low endurance limits. Fatigue damage initiated at an angle to the applied load, but changed direction at a critical length and grew as mode I cracks. However, the initiation stage of fatigue damage was very short, and almost the entire fatigue life was spent in the crack-growth stage.