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Direct measurement of critical cooling rates has been challenging and only determined for a minute fraction of the reported metallic glass forming alloys. Here, we report a method that directly measures critical cooling rate of thin film metallic glass forming alloys in a combinatorial fashion. Based on a universal heating architecture using indirect laser heating and a microstructure analysis this method offers itself as a rapid screening technique to quantify glass forming ability. We use this method to identify glass forming alloys and study the composition effect on the critical cooling rate in the Al–Ni–Ge system where we identified Al51Ge35Ni14 as the best glass forming composition with a critical cooling rate of 104 K/s.

Bulk metallic glasses (BMGs), which readily form amorphous phases during solidification, are increasingly being used in first applications of watch components, electronic casings, and sporting goods. The compositions of BMGs typically include four to six elements. Various political and geological factors have recently led to supply disruptions for several metals, including some present in BMG compositions. In this work, we assess the “criticality” of 22 technologically interesting BMG compositions, compare the results with those for three common engineering alloy groups, and derive recommendations for BMG composition choices from a criticality perspective. The criticality of BMGs is found to be generally much higher compared with those for the established engineering alloys. Therefore, criticality concerns should also be considered in the choice between existing and developing novel BMGs.

The flaw tolerance of bulk metallic glasses (BMGs) is evaluated using a thermoplastic synthesis approach. We found that flaw tolerance quantified by the notch toughness decreases apparently with decreasing radius until a critical value. Below this critical value, measured notch toughness is independent of its radius, revealing a flaw tolerance behavior of BMGs. We explain such flaw tolerance by a critical plastic zone originating from the BMGs' inherent crack tip blunting capability. This zone defines a characteristic distance over which stable shear banding plastic process develops prior to fracture instability. The specific characteristic distance and crack blunting capability vary widely among BMGs, which rationalizes the vast variety in their fracture behavior and suggest specific flaw tolerance. Our finding is encouraging for BMGs' structural applications since flaws smaller than the critical value are increasingly difficult to avoid but are “indistinguishable” in their influence to fracture toughness.

We consider a broad range of 13 BMGs from different alloy systems to represent the material class of bulk metallic glasses (BMGs) and characterize their fracture toughness. To determine the effect of composition on the fracture toughness within one alloy system, we consider alloys in Zr-Al-Ni-Cu and Pd-Ni-Cu-P BMG forming alloy systems, specifically Zrx(Al0.25Ni0.25Cu0.5)100-x (at.%) and Pdx(NiCu2)(80-x)/3P20. Sample preparation follows a thermoplastic forming based method ensuring constant fictive temperature, which allows us to eliminate extrinsic effects and detangle the effect of fictive temperature and alloy chemistry on the fracture toughness. We found that fracture toughness varies significantly with composition, even in a non-monotonic way. Within one alloy system, fracture toughness correlates closely with the ratio of shear modulus over bulk modulus. Such correlation however is not present when comparing BMGs across alloy systems. Observed behavior suggests that shear modulus and bulk modulus serves as an incomplete proxy describing the BMGs ability to resist shear and cavitation. Further, our results reveal a general inverse correlation between fracture toughness and glass forming ability suggesting a trade-off of both desired properties. Such trade-off is not necassary present in metal-metalloid containing BMGs, where our results reveal a possibility to optimize alloys for both GFA and fracture toughness simultaneously.

Bulk metallic glasses (BMGs) exhibit remarkable mechanical properties, such as high strength and elasticity, which is often paired with fracture toughness. Their supercooled liquid region gives rise to plastic-like processing and suggests parts and shapes that can otherwise not be obtained for crystalline metals. However, current processing techniques only allow for limited options in terms of geometry, thicknesses uniformity, and shape complexity. Here we introduce a new processing technique, “stretch blow molding,” to expand the range of possible parts and increase the available geometries that can be fabricated with BMGs. Additionally, a model is derived that allows for the quantification and prediction of stretch blow molding and provides insight into its potential use and limitations. We demonstrate that with stretch blow molding overall strains exceeding 2000% are achievable, compared to the previously reported ∼150% of blow molding. With the ability to stretch blow mold shapes that were previously unachievable with any other metal fabrication technique in a fast and economical manner, and the superb properties of BMGs, we look forward to a broad commercial adaptation of this technique.

3D Metallic glass structures (3DMGs) are fabricated through thermoplastic forming (TPF)-based patterning of MG sheets combined with a parallel joining technique. To demonstrate this capability and benchmark 3DMGs, we have fabricated honeycomb-like MG architectures covering a wide range of relative densities. 3DMGs exhibit high elasticity of up to 40% loading strain, high elastic energy storability, and high energy absorption which is superior compared to those made from other materials such as conventional metals and ceramics, based on our theoretical analysis. The combination of MG properties and introduced versatile fabrication method suggest the possibility of developing a wide range of 3DMGs with excellent performance for specific applications.

A method is introduced to determine notch toughness of bulk metallic glasses (BMGs). Through thermoplastic replication of Si molds, unprecedented control in fabricating BMG toughness samples can be achieved and influences such as cooling rate, thermal history, residual stress, sample geometry, and notch precision are drastically reduced. For the 20 Zr44Ti11Cu10Ni10Be25 BMG samples, we measured a notch toughness of 109 ± 3 MPa m . Such a much smaller scatter than the previously reported suggests reliable properties of BMGs when thermoplastically formed.

En el presente trabajo se prepararon membranas de polidimetilsiloxano con partículas de plata en tamaños nanométrico y micrométrico, así como fibras de carbono. Se evaluó el efecto de la incorporación de los diferentes materiales en las propiedades finales de las membranas. Primero se llevó a cabo la caracterización de los refuerzos de manera individual para las micro y nanopartículas de plata se caracterizaron por medio difracción de rayos X y microscopía electrónica de barrido, las fibras de carbono fueron caracterizadas por difracción de rayos X, microscopía electrónica de barrido, espectroscopia de infrarrojo y espectroscopia de Raman así como por energía dispersiva de rayos X; esto con el objetivo de corroborar las propiedades de los refuerzos antes de incorporarlos al polidimetilsiloxano. Posteriormente se prepararon membranas de polidimetilsiloxano con nanopartículas de plata y micropartículas de plata en concentraciones de 5%, 12%, 20%, 30%, 50%, 60%, 65% y 70% en peso. Para el sistema de polidimetilsiloxano con fibras de carbono las concentraciones utilizadas fueron 1 %, 3%, 5%, y 7% en peso. Las membranas fueron preparadas mediante las técnicas de spin coating para el sistema de polidimetilsiloxano con plata y moldeado estático para el sistema de polidimetilsiloxano con fibras de carbono. Mediante la microscopía de barrido se estudió la dispersión y distribución de los refuerzos en el polidimetilsiloxano. Además ésta técnica se utilizó para determinar los espesores de las membranas obtenidas. Para las membranas de polidimetilsiloxano con fibras de carbono se llevó a cabo la caracterización por medio de espectroscopia de Raman así como análisis por espectroscopia infrarroja por transformada de Fourier y se comprobó que no existen interacciones químicas entre el polidimetilsiloxano y las fibras. Las membranas obtenidas fueron caracterizadas eléctricamente, para esta evaluación se fabricaron diferentes contactos eléctricos en obleas de silicio. Finalmente se diseñó un arreglo matricial de contactos eléctricos para determinar la posibilidad de utilizar las membranas como sensores de presión. En las membranas de polidimetilsiloxano con partículas de plata no se observaron cambios en la resistencia eléctrica, sin embargo, el sistema de polidimetilsiloxano con fibras de carbono si presentó una disminución en su resistencia eléctrica. Ésta propiedad fue evaluada en función de la fuerza aplicada para determinar la viabilidad del uso de las membranas en sensores de presión, de éstas mediciones se determinó que es una opción viable al ser comparada con una membrana comercialmente disponible debido a la disminución de la resistencia eléctrica inicial y a presentar una alta linealidad en el cambio de la resistencia eléctrica conforme se aumenta la fuerza aplicada en la membrana para el rango de valores estudiado.