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ZnMg0.8Ca/Sr0.2 ternary alloys - the influence of the third element on material properties
Čapek, Jaroslav ; Pinc, Jan ; Kubásek, J. ; Molnárová, Orsolya ; Maňák, Jan ; Drahokoupil, Jan
Zinc-based materials alloyed with the elements of the 2nd group of the periodic table have been studied as potential materials for the fabrication of various biodegradable implants. In this study, we prepared two ternary alloys: ZnMg0.8Ca0.2 (wt.%) and ZnMg0.8Sr0.2. The microstructure of both ternary alloys was similar, the main difference was in the size and morphology of the Ca/SrZn13 phase. The SrZn13 phase formed fine particles with a submicron size and had more significant hardening effect in the as-cast state compared to the CaZn13 phase. The annealing led to a transformation of the eutectic structure into the “massive” Mg2Zn11 phase which caused a significant increase of both hardness and compressive yield stress. In the annealed states, comparable hardness was observed for both alloys and higher compressive yield strength for the Ca-containing alloy.
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Neutron investigation of Nitinol stents and massive samples before and after PIRAC coating
Rogante, M. ; Buhagiar, J. ; Cassar, G. ; Debono, M. ; Lebedev, V. ; Mikula, Pavol ; Ryukhtin, Vasil
Nitinol, a thermoelastic Ni-Ti Shape Memory Alloy (SMA) with approximately 50 at. % Ti, is adopted in a wide range of medical equipment and devices used in interventional radiology, orthopaedics, neurology and cardiology, in particular as a smart material for stents. In this work, NiTi real stents and massive samples before and after different Powder Immersion Reaction Assisted Coating (PIRAC) treatments have been investigated by using two neutron techniques: (1) Small and Ultra-Small Angle Neutron Scattering (SANS, USANS) for nano- and micro-scale characterization, obtaining information on structure and the effects due to the coating treatment, and (2) High-Resolution Neutron Diffraction (HRND), evaluating the macrostrain components resulting from angular shifts of diffraction peaks and the micro-strains in the plastically deformation region by means of profile-broadening analysis. The obtained results contribute: improving knowledge of defects and other key features of the materials complementary to those achieved by using traditional examination techniques. helping to better understand the functional characteristics of Nitinol parts and predict the material's mechanical behaviour.
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