The intricate hierarchical microstructures typical of biological materials give rise to fascinating combinations of anisotropic mechanical properties that can surpass those of man-made materials. The linking together of three-dimensional (3D) imaging techniques has the potential to reveal these structures in unprecedented detail. However, a complete understanding can only be reached if the relationship between structure and mechanical properties can be elucidated. X-ray-computed tomography (CT) is uniquely placed to image such structures across a wide range of length scales. We review recent technical advances that are leading to improved contrast and spatial resolution. We highlight how time-lapse CT 3D studies can track the response of hierarchical microstructures to mechanical loading.

Continuous repetitive upsetting and extrusion (CRUE) processing was performed to investigate its effects on microstructures, mechanical properties and texture characteristics of a 2A66 Al–Li alloy. The results show that the average grain size is effectively refined from initial as-extruded ∼140 µm to ∼4 µm after 3 CRUE passes. The grain refinement is the combined effect of continuous dynamic recrystallization and discontinuous dynamic recrystallization. The texture intensity tends to be weaker and new cube texture is gradually developed with increasing CRUE passes. In addition, the fraction of high angle grain boundaries increases to 86.37% after 3 CRUE passes. Tensile test results reveal that the ductility is greatly enhanced with modest reduction in strength after CRUE processing. The variation in mechanical properties may be mainly due to the decrease of dislocation density and weakening of texture.

The electron microscope has made paramount contributions to understanding the structure of biological molecules, cells, and tissues. In general, the most faithful preservation of biological specimens and other soft-organic materials is achieved through cryogenic fixation. The embedding medium is the native aqueous environment itself, immobilized in vitrified form by rapid or pressurized cooling. Until recently, imaging of such vitrified thin specimens by electron cryo-microscopy has been nearly synonymous with wide-field transmission electron microscopy (TEM). Several new approaches have entered the cryo-microscopy field, including soft x-ray imaging, serial surface imaging using focused ion beam scanning electron microscopy, phase plates, and scanning TEM (STEM). In this article, we focus on the STEM method and its adaptation to biological cryo-microscopy. Cryogenic imaging of unstained specimens by STEM introduces specific challenges. Difficulties were long considered insurmountable, and the potential advantages were underappreciated. Future developments in experimental setup and detector technologies will allow for extension of the method to thicker specimens with improved resolution and analytic capabilities.

This paper critically evaluates methods used to synthesize boride compounds with emphasis on diborides of the early transition metals. The earliest reports of the synthesis of boride ceramics used impure elemental powders to produce multiphase reaction products; phase-pure borides were only synthesized after processes were established to purify elemental boron. Carbothermal reduction of the corresponding transition metal oxides emerged as a viable production route and continues to be the primary method for the synthesis of commercial transition metal diboride powders. Even though reaction-based processes and chemical synthesis methods are mainly used for research studies, they are powerful tools for producing diborides because they provide the ability to tailor purity and particle size. The choice of synthesis method requires balancing factors that include cost, purity, and particle size with the performance needed in expected applications.

A novel synchronous rolling-casting for metal (SRCM) process for producing metal components is developed. In this paper, the microstructure evolution and mechanical property of ZLl04 alloy with different pouring temperatures by SRCM are investigated. In the process, the pouring temperature has great effects on the microstructure and mechanical property primarily through the crystal change in the rolling-casting area. Temperature of liquids and solids of ZL104 alloy is measured by differential scanning calorimetry. Distribution and characteristics of the microstructure of samples are examined by optical microscopy, scanning electron microscopy equipped with energy dispersive spectrometer. The results show that the samples fabricated by SRCM present uniform structure and good performance with the pouring temperature at 620 °C when the velocity of the substrate is at 10 cm/s. The tensile strength of ZLl04 alloy reaches 211.89 Mpa, while the average vickers hardness is 81.5 HV.