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The manufacturing process gives cast iron castings properties which are dependent on component design, metallurgy and casting method. Factors such as local wall thickness influences the coarseness and type of microstructure and the castings will have local properties depending on the local metallurgical and thermal history. The stress/strain behaviour of cast materials is typically determined by performing a tensile test in a tensile test machine. The deformation behaviour will normally be determined by two mechanisms, namely, elastic and plastic phenomena. The plastic behaviour is based on dislocation movements in the lattice. Commonly, the deformation history of cast iron involves elastic, plastic and crack phases. The cast iron material has a complex microstructure and first order equations cannot be used to predict the deformation during loading. Until methods have been developed, the characterization of complex microstructure materials such as cast iron has to be determined by use of empirical methods. The empirical methods have to couple the internal microstructure and composition of the material with deformation phenomena during loading. The paper will show a method to characterize tensile test curves of cast iron materials which can be used to couple deformation phenomena with for example microstructure. The equations are aimed to make the tensile test curve ready for curve fitting and optimization in two steps. Each stress/strain curve is like a finger print of the material and requires well performed tests and some advices are given. The paper also wants to encourage researchers and people working with tensile testing to get out more of their effort to measure strength of cast iron materials and connect the result to the microstructure of the specimens. CC BY 4.0

The reported research establishes a semi-analytical computational predictive model of fractal microstructure in ball-milled metal foils and powder particulates, with emphasis on its transformation mechanics via an energy-based approach. The evolving structure is composed of reconfigurable warped ellipsoid material domains, subjected to collisions with the ball milling impactors following Brownian motion energetics. In the first step of the model, impacts are assumed to generate ideal Hertzian elastic stress fields, with associated bulk deformations quantified as per Castigliano's strain energy methods. In the second stage of the model, elastic energies are recast to produce frictional slip and plastic yield, thus resulting in surface micro-joints. Only two parameters of the model necessitate experimental calibration, performed by comparison of joint energy with laboratory tensile measurements on ball-milled multilayer Al-Ni foils. Model predictions of evolving internal microstructure are validated against SEM micrographs of Al-Ni powder particulate samples for different ball milling durations. Results demonstrate the capability of the model to accurately capture relevant fractal measures of the microstructure of ball-milled powders. © 2016 Acta Materialia Inc. 123 305 316 305-316

International audience; Se with good glass formation ability was gradually doped into the Ge-As-Te glasses, and then the gradual change processes of some key physical and optical properties were observed. A series of Ge10As40Te50-xSex(x=0, 10, 20, 30, 40, 50) chalcogenide glass samples were prepared by the traditional melt-quenching method. The internal microstructure, physical and chemical properties of the glass samples were analyzed by using X-ray diffraction, Raman spectroscopy and thermal dilatometer instruments. Vis-NIR absorption spectra and infrared optical transmission spectra of these glasses were recorded with Spectrophotometer and Fourier transform infrared spectroscopy instrument. Then, the Tauc equation was adopted to calculate the direct and indirect optical band gaps of the glass samples. The results show that with the increasing of the Se, the thermal stability can be effectively improved, the maximum Tg can reach up to 233℃. A obvious blue shift of short infrared absorption spectrum cut-off edge appearance is observed in these glasses, i.e. The optical band gap increases gradually, which shows a wider range of transmission and better transparency spectrum, the maximum transmission rate can reach up to 56%. Infrared cut-off edge remains at 20μm, while Se content is less than 2 mol, its thermal stability is improved obviously and the optical spectral changes little. At last, using metal Mg as an oxide redactor for the purification of these glasses, the results show that the transmission spectra is much smooth and without any obvious impurity absorption peaks after the appropriate purification process. © 2016, Science Press. All right reserved.

The scanning electron-induced acoustic microscopy (SEAM) has been developed as a new tool for non-destructive observations of the internal microstructures of materials. It consists of the electric chopper to pulse the high current electron beam and the detector of the longitudinal acoustic waves, being attached to the commercial scanning electron microscopy (SEM). The SEAM gives the best performance for observing the internal defects like the local delamination of the interface in the sub-surface of the semiconductor, because it senses the local difference of thermal properties in the sample. The acoustic waves transmitted from the thermal waves generated near to the surface, in principle, carry the information on such internal defects. In the present paper, the outline of our improvements to the system for getting higher resolution is first stated with emphasis on electric chopper way, sample holder design and image data processing method. Some typical samples of a soldered copper piece, Fe-3%Si and TRIP steels are supplied to ascertain the detectability of the internal microstructures. And then, the effects of the pulsing frequency of the electron beam and the accelerating voltage to the resolution of the electron acoustic images are investigated. The higher resolution can be achieved as the higher pulsing frequency, as suggested by the phenomenological considerations.

International audience; Agglomerated food powders are made from native particles which are assembled to form grains. The present investigation seeks to contribute to a better understanding of the three-dimensional internal morphology of food agglomerates (i.e. different couscous grains made from durum wheat semolina under different agglomeration process conditions) by means of microscopic methods (size, compactness) and X-ray micro-computed tomography (XMT), to bring understanding of the process-structure relationships. The three-dimensional internal morphology of food agglomerates was evaluated by means of X-ray micro-computed tomography (XMT), using a tabletop system with a resolution of several micrometers. XMT was considered to evaluate the internal porosity (or void fraction) as well as the size and spatial distribution of pores inside the grains. Closed porosity values ranged between 0.005 and 0.011. Diameter of internal pores was found to range between 13 and 155 mu m which contribute to control mainly their end-properties. The experimental results were discussed to develop a better knowledge of the process-structure relationships for food agglomerates based on wheat powders, produced by wet agglomeration process. We demonstrated that the shearing conditions during the initial mixing stage significantly contribute to the internal structure characteristics of agglomerates. The cooking treatment is found to largely improve the mechanical strength of the agglomerates.

Los pernos de fibra de vidrio usados en las reconstrucciones de dientes, se han popularizado por poseer un módulo elástico similar a la dentina y color altamente estético, sin embargo han presentado fracasos clínicos de tipo mecánicos por fatiga del perno, por lo que se sospecha que un factor relevante es la calidad microestructural. El objetivo fue evaluar la ultraestructura interna de diferentes marcas de pernos de fibra de vidrio. Se evaluaron en cortes transversales cinco tipos de postes de fibra de vidrio (FRC Postec Plus Ivoclar Vivadent®, Parapost Fiber White Coltene Whaledent®, Parapost Fiber Lux Coltene Whaledent®, Glass Fiber Post Superpost® y Reforpost Rx Angelus®). Al Microscopio Electrónico de Barrido se obtuvieron imágenes a 100μm, 500μm y 2500μm de aumento. Con Photoshop se realizó la conversión de pixel a micra y se calculó: área total, área de defecto, homogeneidad en el diámetro de las fibras y relación fibra–matriz. El sistema más homogéneo, compacto y que no presentó imperfecciones fue el FRC Postec Plus. El Parapost Fiber White mostró los diámetros de las fibras más homogéneos y menor concentración de fibras. El Reforpost Rx presentó mayor número de defectos evidentes. Los pernos de fibra de vidrio presentan diferentes calidades microestructurales, algunos muestran defectos y baja consistencia en sus fibras. La calidad microestructural es un aspecto importante a tomar en cuenta en el momento de seleccionar un perno que requiera un desempeño mecánico adecuado en las reconstrucciones de muñón de dientes anteriores. The fiberglass bolts used in reconstruction of teeth, have become popular for having an elastic modulus similar to dentin and highly aesthetic color, however, have presented clinical failures of mechanical fatigue of the bolt, so it is suspected that a relevant factor is the microstructural quality. Our objective was to evaluate the internal ultrastructure of different brands of glass fiber posts. Cross sections were assessed cinco types of glass fiber posts (FRC Postec Plus Ivoclar Viva dent ®, Coltene Whaledent ParaPost ® Fiber White, Coltene Whaledent ParaPost Lux ® Fiber, Glass Fiber Post superposter ® and Rx Reforpost Angelus ®). With a scanning electron microscope images were obtained at 100μm, 500μm and 2500μm increase. With Photoshop conversion was performed micron pixel and calculated: total area, area of defect, homogeneity in the diameter of the fibers and fiber-matrix relationship. The most homogeneous, compact and not introduced imperfections was the FRC Postec Plus. The White Fiber ParaPost showed fiber diameters homogeneous and a lower concentration of fiber. The Rx Reforpost shows more obvious defects. The fiberglass bolts have different qualities microstructural defects and some show low consistency in its fibers. The microstructural quality is an important aspect to consider when selecting a bolt that requires an adequate mechanical performance stump reconstructions of anterior teeth. 5-14 karladaniela0484@gmail.com somimo@hotmail.com

A set of knitted poly(lactic acid) (PLA) fabrics was ozonated at room temperature for periods ranging from one to 60 minutes in order to identify any accompanying effects on physical properties (specifically whiteness, water-absorbency, flexural rigidity and burst strength), fiber surface integrity or internal microstructure. A significant (ca. 6% after 10 minutes of treatment) initial increase in whiteness was observed, with longer treatment times producing little further change. The fabric’s absorbency and flexibility both increased, the time of wetting having fallen by ca. 20% and the flexural rigidity by ca. 16%, respectively, after 10 minutes of treatment. Fabric strength remained virtually unaffected for short times (up to 10 minutes) of ozonation, although longer treatments caused a measurable drop (ca. 10% after 60 minutes). SEM imaging showed virtually no evidence for surface damage, even after 60 minutes of treatment, whereas peroxide treatment caused massive pitting of the fiber surface. Raman spectroscopy of the ozonated PLA fabrics indicated that the treatment had not affected the internal microstructure of the fibers. Our conclusion is that brief (no more than 10 minutes) room-temperature ozonation is potentially an effective, safe and low-energy alternative to conventional higher temperature peroxide treatment. © 2011, SAGE Publications. All rights reserved.