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Role of ogyxen and nitrogen in mechanical alloying mechanism of Ni-Ti powder mi...
Neves, Filipe; Fernandes, F. M. Braz; Martins, Isabel M.; Correia, J. BritoIn this study, the critical milling behaviour of Ni-Ti powder mixtures was evaluated in relation to the effect of atmospheric gases, more specifically to oxygen and nitrogen. Within the experimental conditions used, it is shown that both gases play an important role in the alloying process and that not only oxygen gas reacts with the mechanically alloyed powders but also nitrogen. The most effective mixing occu...
In situ experiments with synchrotron high-energy x-rays of Ni-Ti alloys produce...
Neves, Filipe; Correia, J. Brito; Martins, Isabel M.; Fernandes, F. M. Braz; Mahesh, K. K.; Stark, A.; Schell, N.The structural evolution that takes place during the homogenization heat treatments of powder metallurgical Ni-Ti- alloys was studied by in situ synchrotron diffraction. It is proposed to get a deeper understanding of this phenomenon by using different types of thermal/mechanical cycles.
Nonconventional production technologies for NiTi shape memory alloys
Neves, Filipe; Fernandes, F. M. Braz; Martins, Isabel M.; Correia, J. Brito; Oliveira, M.; Gaffet, E.; Wang, T. Y.; Lattemann, M.; Suffner, J.; Hahn, H.The development of new production technologies for NiTi Shape Memory Alloys (SMAs) is always challenging. Recently, we introduced two powder metallurgical (PM) processing routes involving mechanical activation of elemental powder mixtures and densification through extrusion or forging. Those processes were named Mechanically Activated Reactive Extrusion Synthesis (MARES) and Mechanically Activated Reactive FOrg...
Microstructure characterization of aluminium syntactic functionally graded comp...
Ferreira, S. C.; Velhinho, A.; Rocha, L. A.; Fernandes, F. M. BrazSyntactic functionally graded metal matrix composites (SFGMMC) are a class of metallic foams in which closed porosity results from the presence of hollow ceramic microspheres (microballoons), whose spatial distribution varies continuously between the inner and the outer section of the part, thus resulting in a continuous variation in properties. In this work, aluminium-based SFGMMC rings were fabricated by radi...
Application of X-ray microtomography to the microstructural characterization of...
Velhinho, A.; Fernandes, F. M. Braz; Ferreira, S. C.; Rocha, L. A.; Vignoles, G.; Cloetens, P.This paper provides a brief overview of the possibilities offered by X-ray computed microtomography, and particularly synchrotron radiation X-ray microtomography, regarding metal matrix composite characterization, emphasis being placed in the case of Al-based functionally graded materials. Examples are provided concerning the characterization of the reinforcement population, interfacial properties, in-situ tran...
Evaluation of SiC-particle connectivity in functionally graded Al/SiCp composit...
Velhinho, A.; Vignoles, G.; Cloetens, P.; Thibault, X.; Boller, E.; Fernandes, F. M. Braz; Rocha, L. A.; Botas, J. D.Reliability of functionally graded metal matrix composites (FGMMCs) for automotive components is still dependent on the detailed knowledge of the mechanisms of the microstructural build-up, for instance on the mechanisms leading to the distribution and relative positions of the reinforcing particles. In order to assess the influence of the SiC particle size on the 3-D inter-particle connectivity in functionally...
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