Development and optimization of novel sulfur-containing Ti-based bulk metallic glasses and the correlation between primarily crystallizing phases, thermal stability and mechanical properties

The effect of sulfur on the glass forming ability, thermal stability and mechanical properties of the eutectic alloy Ti33.4Zr33.3Cu33.3 was investigated by conventional X-ray diffraction, differential scanning calorimetry and 3-point flexural experiments. A novel region of bulk glass formation with a critical casting diameter of up to 4 mm was found in the quaternary Ti-Zr-Cu-S system, however, brittle fracture behavior was predominant. Various alloying strategies were employed to improve mechanical properties and a compositional transition from brittle to ductile fracture has been identified (e.g. for Ti36Zr33.5Cu24.5S6). A change of the primary precipitating phases from a C14 Laves to an intermetallic (Ti,Zr)2Cu phase can be observed, as well as a stabilization of the supercooled liquid. The origin of the thermally unstable behavior in Ti-based bulk metallic glasses is traced back to the easy formation of the icosahedral phase upon heating, which is structurally close to the supposedly predominant icosahedral short-range order in the amorphous state. The systematic study carried out in this work indicates a strong correlation between primary crystallizing phase and thermal stability, both pointing to the frozen short-range order in the amorphous state which is predetermining the mechanical properties. The transition from the Laves to the intermetallic (Ti,Zr)2Cu phase as well as the enlarged supercooled liquid region appear to be directly related to a destabilization of the icosahedral short-range order and ultimately to the improved mechanical properties

DESENVOLVIMENTO REGIONAL ATRAVÉS DAS REDES TURÍSTICAS: REGIÃO FRONTEIRA NOROESTE / REGIONAL DEVELOPMENT THROUGH TOURIST NETWORKS: NORTHWEST FRONTIER REGION

Abstract: Studies on endogenous regional development and association with tourist networks value cooperation and growth of entities and social actors that make up a given location. In this way, a contextualization about the themes was carried out, in order to understand regional development through tourist networks. This study can be understood as a theoretical essay, having the bibliographic survey as a research method. Among the main results, it was found that for there to be an endogenous regional development through a tourist network, it is essential that the collective effort stands out from the particular, with efficient social relations, empowerment of social actors, presence of a tourism system that cherish collective interests and, above all, the importance of participation and tripartite promotion formed by the State, civil community and private companies.Resumen: Los estudios sobre desarrollo regional endógeno y asociación con redes turísticas valoran la cooperación y el crecimiento de las entidades y actores sociales que conforman un determinado lugar. De esta forma, se realizó una contextualización sobre los temas, con el fin de comprender el desarrollo regional a través de las redes turísticas. Este estudio puede ser entendido como un ensayo teórico, teniendo como método de investigación el levantamiento bibliográfico. Entre los principales resultados se encontró que para que exista un desarrollo regional endógeno a través de una red turística es indispensable que el esfuerzo colectivo se destaque del particular, con relaciones sociales eficientes, empoderamiento de los actores sociales, presencia de un sistema turístico que acaricien los intereses colectivos y, sobre todo, la importancia de la participación y promoción tripartita formada por el Estado, la comunidad civil y la empresa privada.Os estudos sobre desenvolvimento regional endógeno e associação às redes turísticas prezam pela cooperação e crescimento das entidades e atores sociais que integram determinada localidade. Desta forma, realizou-se uma contextualização acerca dos temas, a fim de compreender o desenvolvimento regional através das redes turísticas. Este estudo pode ser compreendido como um ensaio teórico, tendo como método de pesquisa o levantamento bibliográfico. Entre os principais resultados, verificou-se que para haver um desenvolvimento regional endógeno por meio de uma rede turística, é primordial que o esforço coletivo se sobressaia ao particular, com relações sociais eficientes, empoderamento dos atores sociais, presença de um sistema de turismo que preze pelos interesses coletivos e, principalmente, a importância da participação e do fomento tripartite formado pelo Estado, comunidade civil e pelas empresas privadas. Abstract: Studies on endogenous regional development and association with tourist networks value cooperation and growth of entities and social actors that make up a given location. In this way, a contextualization about the themes was carried out, in order to understand regional development through tourist networks. This study can be understood as a theoretical essay, having the bibliographic survey as a research method. Among the main results, it was found that for there to be an endogenous regional development through a tourist network, it is essential that the collective effort stands out from the particular, with efficient social relations, empowerment of social actors, presence of a tourism system that cherish collective interests and, above all, the importance of participation and tripartite promotion formed by the State, civil community and private companies

Effect of composition and thermal history on deformation behavior and cluster connections in model bulk metallic glasses

The compositional dependence and influence of relaxation state on the deformation behavior of a Pt-Pd-based bulk metallic glasses model system was investigated, where platinum is systematically replaced by topologically equivalent palladium atoms. The hardness and modulus increased with rising Pd content as well as by annealing below the glass transition temperature. Decreasing strain-rate sensitivity and increasing serration length are observed in nano indentation with increase in Pd content as well as thermal relaxation. Micro-pillar compression for alloys with different Pt/Pd ratios validated the greater tendency for shear localization and brittle behavior of the Pd-rich alloys. Based on total scattering experiments with synchrotron X-ray radiation, a correlation between the increase in stiffer 3-atom cluster connections and reduction in strain-rate sensitivity, as a measure of ductility, with Pd content and thermal history is suggested

VVV-WIT-04: An extragalactic variable source caught by the VVV Survey

We report the discovery of VVV-WIT-04, a near-infrared variable source towards the Galactic disk located ~0.2 arcsec apart from the position of the radio source PMN J1515-5559. The object was found serendipitously in the near-IR data of the ESO public survey VISTA Variables in the V\'ia L\'actea (VVV). Our analysis is based on variability, multicolor, and proper motion data from VVV and VVV eXtended surveys, complemented with archive data at longer wavelengths. We suggest that VVV-WIT-04 has an extragalactic origin as the near-IR counterpart of PMN J1515-5559. The Ks-band light-curve of VVV-WIT-04 is highly variable and consistent with that of an Optically Violent Variable (OVV) quasar. The variability in the near-IR can be interpreted as the redshifted optical variability. Residuals to the proper motion varies with the magnitude suggesting contamination by a blended source. Alternative scenarios, including a transient event such as a nova or supernova, or even a binary microlensing event are not in agreement with the available data.R.K.S. acknowledges support from CNPq/Brazil through projects 308968/2016-6 and 421687/2016-9. P.W.L. is supported by STFC Consolidated Grant ST/R000905/1. Support for the authors is provided by the BASAL CONICYT Center for Astrophysics and Associated Technologies (CATA) through grant AFB-170002, and the Ministry for the Economy, Development, and Tourism, Programa Iniciativa Cient´ıfica Milenio through grant IC120009, awarded to the Millennium Institute of Astrophysics (MAS). D.M. acknowledges support from FONDECYT through project Regular #1170121

Laser powder bed fusion of Cu-Ti-Zr-Ni bulk metallic glasses in the Vit101 alloy system

Laser powder bed fusion (PBF-LB/M) of bulk metallic glasses (BMGs) has experienced growing scientific and industrial interest in the last years, with a special focus on application relevant systems based on zirconium. The high cooling rates and the layer-wise build-up process allow overcoming size and geometry limitations typical for conventional casting routes. Yet, the novel production approach requires different alloy characteristics than casting processes. The present work reports for the first time on the PBF-LB/M-processing of three CuTi-based bulk metallic glass formers in the Vit101 system, allowing to exceed the mechanical performance of most additively formed Zr-based BMGs. Furthermore, the influence of alloy properties like thermal stability and toughness on the PBF-LB/M applicability are systematically studied. Thermal stability plays a minor role to produce amorphous specimen, while notch toughness is found to be a more crucial aspect to achieve parts with low defect density and resulting high mechanical performance. The results suggest fundamentally different alloy development strategies adapted to the needs of the PBF-LB/M-process, leaving classical casting-based optimization of glass forming ability behind and evolving towards a rather toughness-oriented optimization

Ni-Nb-P-based bulk glass-forming alloys: Superior material properties combined in one alloy family

Ni-Nb-based bulk glass-forming alloys are among the most promising amorphous metals for industrial applications due to their incomparable combination of strength, hardness, elasticity and plasticity. However, the main drawback is the limited glass-forming ability, narrowing the field of application to solely small components. In this study, we show that minor additions of P to the binary Ni-Nb system increase the glass-forming ability by 150 % to a record value of 5 mm. P can be easily added by using an industrial Ni-P pre-alloy which is readily available. The partial substitution of Nb by Ta further boosts the glass-forming ability to values 200 % higher than that of the binary base alloy. Besides conventional X-ray diffraction measurements, the amorphous nature of the samples is verified by high-energy synchrotron X-ray diffraction experiments. Moreover, the mechanical properties of the new alloy compositions are characterized in uniaxial compression tests and Vickers hardness measurements, showing a high engineering yield strength of 3 GPa, an extended plastic regime up to 10 % strain to failure and an increase of the hardness to a maximum value of 1000 HV5. Additionally, calorimetric measurements reveal that the modified alloys feature an extended supercooled liquid region up to 69 K upon heating, permitting thermoplastic micro molding of amorphous feedstock material

Ni-Nb-P-based bulk glass-forming alloys: Superior material properties combined in one alloy family

Ni-Nb-based bulk glass-forming alloys are among the most promising amorphous metals for industrial applications due to their incomparable combination of strength, hardness, elasticity and plasticity. However, the main drawback is the limited glass-forming ability, narrowing the field of application to solely small components. In this study, we show that minor additions of P to the binary Ni-Nb system increase the glass-forming ability by 150 % to a record value of 5 mm. P can be easily added by using an industrial Ni-P pre-alloy which is readily available. The partial substitution of Nb by Ta further boosts the glass-forming ability to values 200 % higher than that of the binary base alloy. Besides conventional X-ray diffraction measurements, the amorphous nature of the samples is verified by high-energy synchrotron X-ray diffraction experiments. Moreover, the mechanical properties of the new alloy compositions are characterized in uniaxial compression tests and Vickers hardness measurements, showing a high engineering yield strength of 3 GPa, an extended plastic regime up to 10 % strain to failure and an increase of the hardness to a maximum value of 1000 HV5. Additionally, calorimetric measurements reveal that the modified alloys feature an extended supercooled liquid region up to 69 K upon heating, permitting thermoplastic micro molding of amorphous feedstock material