List of figures Page Figure 1.1 DSC scan of Zr44Ti11Cu20Be25 showing heat capacity characteristics 1.3. It is interesting to note that the theoretical additive viscosity case corresponds to the flow seen in figure 6.5, suggesting that we can approximate the immiscible fluids resisting an indefinite extension case, proposed in [1] on page 87.
Introduction 1.1 History
Physics of Metallic Glasses
A glass at room temperature can be reheated above Tg to a viscous liquid state in which the mobility of the atoms increases as a function of temperature. At temperatures lower than Tn, the thermodynamic driving force is greater, but the mobility of the atoms is too low.
Time
Applied Physics (for processing) in Metallic Glasses
However, processing a BMG using a method similar to injection molding in SCLR requires high thermal stability of the glass during heating. Another method to measure the formability of glass alloys in SCLR was suggested by Schroers [29].
Process in entire Δ T region dT/dt = 10 K/min
This could be a simple way to eliminate many compounds from consideration as potential alloys for plastic forming processes in the SCLR. The diameter of the flattened disk would be a measure of ductility, with larger diameters indicating higher ductility in the SCLR.
Sample size= 0.1 cm 3
Schroers proposed that 0.1 cm3 of material could be compressed between parallel plates via the SCLR under a specified load and at a constant heating rate until crystallization of the glassy material stopped the flow. The basic idea is to integrate the area between the viscosity line at infinite temperature and the η(T) equation over the SCLR.
Final Diameter indicates thermoplastic formability
Advantages of Thermoplastic Processing and State of the Field in 2005 Most practical applications of MG demand near net-shaping process in
Thermoplastic forming methods take advantage of the kinetic stability of an alloy at temperatures below the crystallization nose. The formation of amorphous metal sheets limits the thickness of the final sample and the available part geometries.
![Figure 1.6: Thermoplastic forming demonstrations 2005-2007 [30-31, 36-37].](https://thumb-ap.123doks.com/thumbv2/123dok/11220178.0/32.918.154.785.466.1026/figure-thermoplastic-forming-demonstrations-2005-2007-30-31.webp)
Alloy Development Strategies
Using this previous work by Tanner and the ternary phase space simplification, we were able to significantly reduce the number of alloys needed to explore the compositional space. DSC plots of the ternary alloys and the quaternary alloy, which could be thought of as Cu substitution for the various elements, are included in Figure 1.8.
Temperature [C]
What To Do with All These Alloys
The crush test showed that Zr35Ti30Be27.5Cu7.5 has the best potential for TPF of all the tested alloys. A more detailed study of the flow properties of these materials with two Tg events is included in Chapter 6 of this thesis.
- Introduction Summary
If this two-phase analysis is correct, the endpoints of the miscibility gap have been discovered and the phases into which the alloy separates are known. If we had microscopic evidence of the two phases, we could argue that all the Fe went to the Ti rich phase and therefore all spectra looked like the.
Cylindrical rods of 3 mm diameter x 6 mm height were used to measure the mechanical properties of Ti-based light glass alloys on an Instron testing machine at a strain rate of 1*10-4 s-1. These lightweight amorphous titanium-based alloys also have higher specific strengths than crystalline titanium alloys.
ZrTi Based Be Bearing Glasses Optimized for High Thermal Stability and Thermoplastic Formability
- Introduction
- Experimental Method
- Results and Discussion
- Conclusion
Essentially, such thermoplastic forming ability arises as a result of the thermal stability and fragility of the supercooled fluid. It is interesting to note that the scans of the alloys of Figure 3.3 show a single exothermic peak after the glass transition, suggesting that these alloys tend to crystallize by simultaneous crystal growth. A summary of the alloys with the largest ΔT from each of the quaternary families is shown in Figure 3.5.
Perhaps the simplest approach would be to estimate ternary phase diagrams from known binary phase diagrams using a.
Bulk Metallic Glass with Benchmark Thermoplastic Processability After discovering the large ΔT alloys discussed in Chapter 3, we characterized the
- Experimental Method
Data at the bottom of the nose were collected by warming the metallic glass from room temperature. The data on the top of the nose were obtained by cooling the material from the melt. Before TPF was performed, we produced diamond-shaped (~100μm) microindentation patterns on the top flame of the coin using a Vickers hardness tester (Figure 4.4c).
For the viscosity measurements, the resonant oscillation of the molten droplet was induced by an alternating current electric field while keeping the sample at a predetermined temperature. Viscosity was calculated from the decay time constant of free oscillation that followed the excitation pulse. We also thank the support of the MRSEC program (Center for the Science and Engineering Materials, CSEM) of the National Science Foundation under Grant number DMR - 0520565.
Injection Molding Metallic Glass
The injection molding process appears to have had little effect on the thermodynamic properties measured in DSC. The short fill shown in Figure 5.3a was due to the piston being attached to the tank. The discovery of Zr35Ti30Be27.5Cu7.5 alloy with SCLR viscosity up to 104 Pa allowed to demonstrate the injection molding of a metallic glass.
Relaxation Phenomena in the ZrTiBe System 6.1 Abstract
- Introduction
- Experimental Method
- Results and Discussion
Heat capacity measurements using DSC have shown that some glassy alloys have two heat capacity discontinuities when heated. The two jumps in heat capacity are labeled Δcp1 and Δcp2 and are shown in Figure 6.1. Liquids with low brittleness show smaller jumps in heat capacity at the glass transition temperature because T*Δcp = Sconfig.
Rule of Mixtures Iso-Be
The rule of mixture analysis predicted the compositions in which a single-phase glass would exist and we now have some evidence of the compositions in which the two-phase glasses separate. Note that the glass transition temperatures of each phase are quite consistent between the two-phase and single-phase glasses and that the overall heat capacity jumps Δcp1 + Δcp2 are similar along each isoBe line. The ZrTiBe glasses differ from the Vitreloy glasses in that they exhibit the two-phase behavior without any annealing in the SCLR.
Miscibility Gap Be = 40
In two-phase amorphous alloys (ZraTi1-a)60Be40, we would expect three regions of flow. We also see a compositional effect causing lower measured viscosities at a given temperature for alloys with higher proportions of the low Tg phase. The horizontal area in the graphs of η(T) at Tg2 is not understandable and may be the result of the small diameter of the tested samples.
Region 2 Region 3
- Conclusion
There are two changes in the slope of G(T), which roughly correspond to the two glass transition temperatures. This is further evidence of two relaxation events in the SCLR of these alloys, showing the apparent double glass transition. The observed double relaxation phenomena in the SCLR of the studied alloys are not yet fully understood.
An explanation proposing a single glass transition with an exothermic ordering event is unlikely to be sufficient to describe the relaxation phenomena observed in these experiments.
Conclusion
- Future Research Directions
The discovery of bulk glass formers in the ZrTiBe system facilitated a better understanding of the SCLR of these alloys and enabled the clear observation of two relaxation phenomena in the SCLR that are likely phase-related. If no phase separation is detected, an alternative analysis of the physics behind the two Tg phenomena observed in the SCLR of these alloys could be explored. Another method already being explored by Johnson's group is abbreviated RDF, Rapid Discharge Formation (not a radial distribution function).
Parts exceeding the critical alloy casting thickness could even be produced if sufficient time is available to cool in the SCLR, and as shown in Chapter 5, parts resulting from TPF are more reliable than parts cast under pressure, and show similar strength with less dispersion in strength. Part geometries are probably more limited than what higher ΔT alloys could achieve, but alloys that exhibit desirable properties but with poor GFA would become much more useful.
Corrosion Properties of ZrTiBe + Me Alloys in HCl
The corrosion rate and the standard half-cell potential of the element Me are related and show a log-linear relationship. The rates were highly dependent on the "nobility" or standard half-cell potential of the alloying element. The logarithm of the corrosion rate appears to be linearly correlated with the standard half-cell potential or the nobleness of the alloying element, where more noble elements counterintuitively produce higher corrosion rates.
One Year Rabbit Implantation Study of a Zirconium Based Beryllium Bearing Metallic Glass
In the second and third tests, specific Pathogen Free New Zealand White Rabbits were tested. In the second test, rabbits were treated with isotonic saline extracts of LM1 and LM2. In the third test, isotonic saline and cottonseed oil extracts of LM1 and LM2 were injected intradermally into the back of the rabbits.
None None - cortical hole present with or without periosteal lining. 4 Chronic widespread and predominantly lymphocytic inflammation 4 Focal chronic inflammation in a thick capsule region 5 Intracapsular inflammation predominantly lymphocytes, however occasional neutrophils are identified (~1 high power field) Inflammation is located in the thickest part of the capsule. 6 Chronic inflammation - focal and localized in the thick part of the fibrosis 7 Chronic focal inflammation located perivascularly in the extracapsular region and the adjacent capsule 8 Marked, diffuse chronic inflammation involving the entire circumference 9 Mixed acute/chronic inflammation focally 10 Mixed focal inflammation in a region of capsular thickening and diffuse inflammation1. accompanied by thick capsular regions 12 Chronic focal inflammation.
Corrosion and Corrosion Fatigue of Vitreloy Glasses Containing Low Fractions of Late Transition Metals
For example, the corrosion resistance of ZrTiNiCuAl glass (Vitreloy 105) in phosphate-buffered saline (PBS) was found to be equal to or slightly lower than commonly used metallic biomaterials such as stainless steels, Ti-6Al-4V and CoCrMo [6 ]. . Despite the generally good corrosion behavior of BMG-type Vitreloys, their stress corrosion behavior. The improvement in corrosion resistance, however, is not accompanied by an analogous improvement in corrosion fatigue resistance, revealing that the two processes are controlled by different physical mechanisms.
Cyclic Anodic Polarization
For Vit 105, four-point bending fatigue and corrosion fatigue data from the study of Morrison et al. The relationship of fatigue limit to yield stress in air and in salt solution for the three BMG is listed in Table A3.1. Data for 18/8 stainless steel, Alclad 24S-T and Monel taken from Atlas of Fatigue Curves and other sources [11-15] are also displayed in Table A3.1.
Cycles to Failure (N F )
- M NaCl
- References
- Derivations
- Fourier Heat Equation We begin with the Fourier heat equation
- Implications of Slope Change in Thermodynamic Variables Assume a slope change in the entropy S(T) or enthalpy H(T) of a material. Call the
- Stephan’s Equation for Parallel Plate Viscometer
In stress (or cyclic stress) corrosion conditions, the mechanical stability of the passive layer is also important. Mechanical rupture of the passive layer is expected to result in severe chemical attack concentrated at the tip of the extended crack. Assume that the temperature of the material when it is poured into the mold at t = 0 is U(x,0) = TL or the liquidus temperature.
- Vogel-Fulcher-Tammann Viscosity
- Viscosity of BMG from Potential Energy Landscape Perspective Flow of a metallic glass is described as barrier crossing events in “Rheology and
- Composition Counting
- Limiting Cases of Two Phase Liquid Flow
- Modulus of Rupture Equation for Rectangular Beam Modulus of Rupture for beam bending
- References
We integrate as shown in Figure A4.1 by greatly simplifying the BMG physics and assuming that all BMGs exhibit the same viscosity at Tx. This case is best handled with a quaternary phase diagram drawn in 3D due to the constraint as shown in Figure A4.4. Where F is the applied shear stress, η is the viscosity and dr. dv is the spatial derivative of the velocity orthogonal to the shear direction.
