Deformation of metallic glasses requires the existence of free volume to allow atomic movement under mechanical loading. Accordingly, the present research seeks to understand how free volume variations in alloys of identical compositions affect the fatigue and fracture behavior. By annealing below the glass transition temperature, the free volume of...
Deformation of metallic glasses requires the existence of free volume to allow atomic movement under mechanical loading. Accordingly, quantification of the free volume state of the alloy is crucial to understand it's mechanical behavior. By annealing below the glass transition temperature, the free volume of a Zr₄₄Ti₁₁Ni₁₀Cu₁₀Be₂₅ bulk metallic glass...
Depth-profiled Doppler broadening spectroscopy of positron annihilation on the cyclic fatigue-induced fracture surfaces of three amorphous Zr₄₄Ti₁₁Ni₁₀Cu₁₀Be₂₅ metallic glass specimens reveals the presence of a 30–50 nm layer of increased free volume that is generated by the propagating fatigue crack tip. The presence and character of this fatigue transformation zone...
Bulk metallic glasses (BMGs) offer a great deal of potential through their near-theoretical strength, potentially high toughness and unique forming and molding traits. However, there are still a number of outstanding issues that bar their widespread use. This thesis describes the investigation of three research questions each designed to further...
Energetic resources transferred between distinct habitats or ecosystems, referred to as allochthonous resources, can greatly subsidize consumers in the recipient habitat, and thus influence food web structure and dynamics. Such subsidies may allow the growth of the consumer population to be decoupled from in situ productivity with effects on consumer...
The fracture toughness is a critical material property that determines engineering performance.
However, as is well known for crystalline materials, if certain sample geometry and size
requirements are not met, test results become sample-size dependent and difficult to compare
among different studies. Here, the room-temperature fracture toughness of the Zr-based...
Full Text:
glasses
Size-dependent fracture toughness of bulk-metallic glasses
Gludovatz, B., Naleway, S. E
The strength-normalized fatigue endurance strength of the bulk metallic glass (BMG) Zr₅₂.₅Cu₁₇.₉Ni₁₄.₆Al₁₀Ti₅ (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...
The influence of shear rate and temperature on the viscosity and fragility of the Zr₄₁.₂Ti₁₃.₈Cu₁₂.₅Ni₁₀.₀Be₂₂.₅ (Vit1) metallic glass forming liquid is measured in the liquid and undercooled liquid state between 907 and 1300 K. The results show a complex rheological behavior of Vit1. The viscosity of Vit1 is about three...
The effect of ambient environment on the fatigue behavior of two Zr-Ti-Cu-Ni-Be bulk metallic glasses (BMGs) is examined in the present study. The first metallic glass, Zr₄₄Ti₁₁Ni₁₀Cu₁₀Be₂₅, was tested to establish the presence of an environmental effect in the fatigue growth curve measured in ambient air. Fatigue growth curves produced...
The slow β relaxation is understood to be a universal feature of glassy dynamics. Its presence in bulk metallic
glasses (BMGs) is evidence of a broad relaxation time spectrum that extends to deep within the glassy state.
Despite the breadth of research devoted to this phenomenon, its microscopic origin is...