Commercially available fiber Bragg grating (FBG) sensors cannot be used for measuring cryogenic temperatures because they are made of silica the thermal expansion coefficient of which tends to zero when approaching 4 K. Because of the many advantages of fiber optic sensors with respect to conventional ones, in this paper it is shown how to circumvent such a limitation by applying a proper metal coating. This approach drastically increases temperature measuring capability of FBGs at cryogenic environments typically encountered in application involving liquid gases or in space. Various metals have been deposited by electro winning on the external fiber surface previously treated with an aluminum precoating. Also, a special casting process has been developed. The explored temperature region was 4.2-40 K. The paper reports the characterization of FBG sensors coated with different metals and shows the validity of this new temperature sensor with respect to conventional ones.

Intermetallic titanium aluminides have attracted considerable industrial interest for aero and automotive applications owing to their specific strength. These alloys are candidates for high-temperature applications such as turbine blades and turbocharger turbine wheels. In this work, the mechanical behaviour of an as-cast Ti–47Al–3Cr–3Nb (at.-%) alloy was studied. Four-point bending tests were performed to determine the mechanical properties of the alloy at both room and high temperatures. Microhardness and Young's modulus were evaluated by dynamic indentation tests at room temperature. Analyses of the as-cast alloy showed that, with the selected production process conditions, it has a duplex microstructure. Tests revealed that, while at room temperature the alloy is brittle, between 700 and 900°C it exhibits good ductility and mechanical properties.

In this work selective laser melting was successfully utilized to produce 316 stainless steel bulk specimens. Although this technology provides many advantages compared to conventional shaping processes, little residual porosity may be a problem for some applications where high strength is required. The objective of this work was to determine, through data analysis, a mechanical and metallographic comparison between thin sheets made by using different manufacturing technologies: Cold rolling and additive manufacturing. This comparison was useful to understand whether it could be more advantageous to use the prototyping for new mechanical components. The results show that the additive manufactured steel, due to its microstructure, is characterized by a higher yield strength and by a lower elongation and ultimate tensile strength.