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In metal powder, shaping the preparation and characterization of the feedstock is an aspect commonly recognized as fundamental. An optimized composition is required to ensure the successful shaping of the feedstock. In this study, a commercial binder system, pure aluminum and 316L austenitic stainless-steel powders were used for micro hot embossing. The optimization process revealed that powder characteristics such as shape and the stability of the torque mixing, were important parameters. Manipulating the feedstock composition by adding multi-walled carbon nanotubes or stearic acid or using a higher powder concentration considerably influenced the torque mixing values. The steady state of torque mixing was achieved for all feedstocks. This torque behavior indicates a homogeneous feedstock, which was also confirmed by microscopic observations. Nevertheless, an extruding process was required for greater homogeneity of the aluminum feedstocks. The presence of the carbon nanotubes increased the homogeneity of green parts and reduced microcrack formation. The roughness was essentially dependent on the feedstock composition and on the plastic deformation of the elastomer die. Shaping the prepared feedstocks (with or without carbon nanotube) was achieved by the optimized powder concentrations and it did not increase by the stearic acid addition.

The joining of alumina (Al2O3) to γ-TiAl and Ti6Al4V alloys, using Ag-Cu sputter-coated Ti brazing filler foil, was investigated. Brazing experiments were performed at 980 °C for 30 min in vacuum. The microstructure and chemical composition of the brazed interfaces were analyzed by scanning electron microscopy and by energy dispersive X-ray spectroscopy, respectively. A microstructural characterization of joints revealed that sound multilayered interfaces were produced using this novel brazing filler. Both interfaces are composed mainly of α-Ti, along with Ti2(Ag,Cu) and TiAg intermetallics. In the case of the brazing of γ-TiAl alloys, α2-Ti3Al and γ-TiAl intermetallics are also detected at the interface. Bonding to Al2O3 is promoted by the formation of a quite hard Ti-rich layer, which may reach a hardness up to 1872 HV 0.01 and is possibly composed of a mixture of α-Ti and Ti oxides. Hardness distribution maps indicate that no segregation of either soft or brittle phases occurs at the central regions of the interfaces or near the base Ti alloys. In addition, a smooth hardness transition was established between the interface of Al2O3 to either γ-TiAl or Ti6Al4V alloys.

Chips are obtained by subtractive processes such as machining workpieces and until recently considered as waste. However, in recent years they are shown to have great potential as sustainable raw materials for powder technologies. Powder production from metal chips, through the application of solid-state processes, seems to be an alternative to conventional atomization from liquid cooled with different fluids. However, chip material and processing have an essential role in the characteristics of powder particles, such as particle size, shape, size distribution and structure (4S’s), which are essential parameters that must be considered having in mind the powder process and the metallurgy applications. Moreover, different approaches refereed in the application of this new “powder process” are highlighted. The goal is to show how the actual research has been transforming subtractive processes from a contributor of wastes to clean technologies.

Hot embossing is a small-scale, low-cost processing technology that can deliver products to the market in a short time. This microreplication technology is well established to produce polymeric components and has applications in several industrial sectors. The use of micropowder hot embossing in the production of metal components is an emerging and challenging process that, when compared to other typical technologies, brings some economic advantages in a volatile market with an increasing tendency to manufacture customized products. The main objective of this review is to analyze the potential of powder hot embossing and its developments in the production of metallic microparts/components. This technology requires four distinct steps: (1) production feedstock (preparation of mixtures), (2) hot embossing (shape forming), (3) debinding and (4) sintering. These steps are interrelated and influence the characteristics of the final metallic microparts. This study summarizes the approaches implemented for the use of different metallic powders and polymeric binder systems for the preparation of the feedstock, the mold materials and the critical conditions tested in the embossing step to produce green parts, and the production of the final parts through the application of debinding and sintering. Powder hot embossing is a viable replication technology that allows the production of new metallic microcomponents, contributing to the global scientific effort of miniaturizing manufacturing process, equipment and products. The merit of powder hot embossing for industrialization needs further development to assert itself in the market and compete with other micromanufacturing techniques.

The development of biomaterials, particularly metallic ones, is one of the focuses of the scientific community, mainly due to an increase of average life expectancy and an improvement of the casted materials combined with better mechanical properties and defect-free products. The use of cobalt alloys in applications, such as knee, hip, and dental prostheses, is the result of their good ability to maintain mechanical properties and biocompatibility over long periods of use. Numerical methods are becoming more important, as they help product improvement in a faster and economic way. This work focuses on the development of a numerical model in ProCAST®, comparing the shrinkage porosity and cooling curves with real castings. When correlating simulation results with available experimental data, it is possible to understand that the formulated model demonstrates an acceptable solution in terms of precision (shrinkage porosity and cooling curve). The alloy’s thermal properties and heat conditions were iteratively changed until the developed numerical model turned out a viable tool for this specific alloy when used in the investment casting process.

Magnetic pulse welding can be considered as an advanced joining technique because it does not require any shielding atmosphere and input heat similar to conventional welding techniques. However, it requires comprehensive evaluations for bonding dissimilar materials. In addition to processing parameters, the surface preparation of the components, such as target material, needs to be evaluated. Different surface conditions were tested (machined, sand-blasted, polished, lubricated, chemically attacked, and threaded) using a fixed gap and standoff distance for welding. Microstructural observations and tensile testing revealed that the weld quality is dependent on surface preparation. The formation of waviness microstructure and intermetallic compounds were verified at the interface of some joints. However, these conditions did not guarantee the strength.

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