Nanocrystalline metals demonstrate a range of fascinating properties, including high levels of mechanical strength. However, as these materials are exposed to high temperatures, it is critical to determine the grain size evolution, as this process can drastically change the mechanical properties. In this work, nanocrystalline sputtered Cu thin films with 43 +/- 2 nm grain size were produced by dc-magnetron sputtering. Specimens were subsequently annealed in situ in a transmission electron microscope at 100, 300 and 500 degrees C. Not only was grain growth more evident at 500 degrees C but also the fraction of twins found. An analysis of grain growth kinetics revealed a time exponent of 3 and activation energy of 35 kJ mol(-1). This value is explained by the high energy stored in the form of dislocation, grain boundaries and twin boundaries existing in nanocrystalline copper, as well as the high probability for atoms to move across grains in nanocrystalline materials.

Alternating nanometric layers of titanium and aluminium were used as filler material to promote joining between titanium aluminide samples. The improved diffusivity of these nanometric layers is thought to overcome the difficulties in solid-state joining of titanium aluminides without producing chemical discontinuities at the interface. In this study, a thin multilayer (alternating titanium and aluminium layers), 2 mm thick, was deposited by dc-magnetron sputtering onto the two surfaces to be joined. The effects of processing conditions and the thickness of nanometric layers on microstructure and chemical composition variation across the interface have been analyzed. Sound regions can be obtained at temperatures as low as 600 C but higher temperatures (800e1000 C) are needed to obtain completely sound joints. During processing, the asdeposited film evolves to a nanocrystalline TiAl layer which may explain why the bond region is slightly harder than the base material.

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The use of replicative processes has become strategic and critical in industry to produce precise, microscopically detailed metallic parts and devices via low cost manufacturing routes. Metal powder hot embossing is an emerging process that brings some advantages associated with the reduction of production costs relative to powder injection moulding (PIM). The technology involves four distinct steps: preparation of the selected feedstock material (powder and binder); hot embossing; debinding; and sintering. The effect of continuous pressure during the hot embossing step as a means of replicating microdetails in 316L stainless steel parts is examined. Dimensional accuracy, microstructure and mechanical properties of the parts produced were evaluated. For the configuration tested, the most promising results were achieved when processing at 180°C for 30 min at a pressure of 14 MPa.