Improved mechanical properties of porous nitinol by aluminum alloying

Aluminum alloying effects (up to 2 at %) on the macrostructure, microstructure, and mechanical properties of porous nitinol (NiTi) obtained by self-propagating high-temperature synthesis (SHS) were studied. It has been established that Ni and Ti interactions with liquid Al (0.5–1 at % Al) in the SHS process significantly change macrostructure, decrease the size of the interpore bridges, and increase their number, resulting in a larger effective cross-sectional area. An increase in the aluminum content above 1 at % leads to larger interpore bridges in the SHS product. The microhardness of TiNi(Al) increases from 305 HV50 g to 422 HV50 g with aluminum concentration, while the fraction of the TiNi(Al) (B2 + B19′) phases decreases from 75% to 50%. The Ti2Ni(Al) phase fraction increases from 25% to 50% with Al concentration. The 64 MPa tensile strength and 2.9% fracture strain of porous Ti50Ni49Al1 alloy are higher than without Al. The increase in strength is due to the formation of a more homogeneous macrostructure and solid solution strengthening of the alloy-forming phases

Study of the effect of diamond nanoparticles on the structure and mechanical properties of the medical Mg–Ca–Zn magnesium alloy

The paper addresses the production and investigation of the Mg–Ca–Zn alloy dispersionhardened by diamond nanoparticles. Structural studies have shown that diamond nanoparticles have a modifying effect and make it possible to reduce the average grain size of the magnesium alloy. Reduction of the grain size and introduction of particles into the magnesium matrix increased the yield strength, tensile strength, and ductility of the magnesium alloy as compared to the original alloy after vibration and ultrasonic treatment. The magnesium alloy containing diamond nanoparticles showed the most uniform fracture due to a more uniform deformation of the alloy with particles, which simultaneously increased its strength and ductilit

Microstructure and biodegradation performance of Mg–4Ca–1Zn based alloys after ultrasonic treatment and doping with nanodiamonds for biomedical applications

This work aims to study microstructural features, phase composition, topology, surface potential, and the biodegradation performance of Mg–4Zn–1Ca-based alloys whose melts were ultrasonically (US) treated and doped with nanodiamonds (ND). The findings show a correlation between the ratio of the secondary phase segregated along the grain boundaries and the biodegradation rate in the RPMI-1640 synthetic culture medium. The fewer Ca2Mg6Zn3 phase fraction, the lower the biodegradation rate. Also, ND doping does not significantly affect the biodegradation rate. Intriguingly, the latter in the US-treated alloy was found to be noticeably inhibited due to a smoother topography and the presence of the fewest Ca2Mg6Zn3 phase fraction segregated along the grain boundaries. Further studies are needed to assess the biodegradable potential of the ND doped alloy, which melt was ultrasonically treated

Perspectives of using a microsurgical device made of titanium nickelide in complicated cataract surgery

Purpose. To examine the possibility of using a tool with variable shape geometry of the operational section of titanium nickelide for small incision surgery to remove complicated cataract.Material and methods. Cadaveric eyes of 7 patients with complicated cataract were used for the study. Nickel titanium alloy was selected as the material for lens destruction, as it meets the medical requirements for design solutions of this class of surgical tools in cycles of their deformation in active and transportation conditions. The instrument operational mechanism is shaped as a loop of superelastic thin thread of titanium nickelide with a diameter of 60 microns with a porous surface coating, is used for mechanical fragmentation of the lens nucleus in complicated cataracts.Results. The size of tissue incision in the access zone is reduced. There is a decrease in capsular bag mobility at the stages of nucleus lens fragmentation. The risk of complications caused by a negative energy and other impacts on eye structures related to ultrasound fragmentation of lens nucleus in complicated cataracts is reduced.Conclusion. Use of such opportunities as material superelasticity, plasticity and strength, and its cutting properties when changing the shape of operational part of titanium nickelide micro-tool contributes to improving the intervention efficiency under complicated cataracts in small incision surgery