In this paper, we study the corrosion-resistant austenitic steel Fe-0.02C-18Cr-8Ni for medical applications. The microstructure and mechanical properties (tensile mechanical properties, torsional strength, impact toughness, and static and cyclic crack resistance) under different types of loading of the steel are investigated. The results are compared for the two states of the steel: the initial (coarse-grained) state and the ultrafine-grained state produced by severe plastic deformation processing via equal-channel angular pressing. It is demonstrated that the ultrafine-grained steel 0.08C-18Cr-9Ni has essentially better properties and is very promising for the manufacture of medical products for various applications that experience various static and cyclic loads during operation.

We present experimental facts on the role of electrolyte pH in shape control of electrodeposited small silver microcrystals. Increasing electrolyte pH value, i.e. the transition from acidic to alkali solutions, causes the change of microcrystal habitus from strongly distorted (pH ß 4) through faceted (pH ß 7) to smooth hemispheric (pH ß 10) ones. At neutral pH ß 7 the observed silver microcrystals demonstrated shapes with pentagonal symmetry including icosahedral microcrystals with incoming pentagonal facets at the icosahedron vertices that is unique for single-component small metallic particles. Such faceting has previously been reported only for bicompounent B 6 O icosahedral small particles [H. Hubert et al., Nature 391, 376 (1998)].It is well known, that the size of a physical object is an important parameter substantially determining its properties [1]. At the range of nano-and microscale small particles and microcrystals often demonstrate nontrivial features. In particular, decahedral or icosahedral morphology is documented for small particles for materials with FCC crystal structure [2-6]. Such particles are referred to as pentagonal small particles (PSPs). Decahedral small particles (DSPs) and icosahedral small particles (ISPs) can be composed of, respectively, five and twenty weakly distorted tetrahedral single-crystal regions. An individual tetrahedron possesses FCC closepacked crystal structure. Neighbor tetrahedra are joined on {111}-type crystallographic planes, which become twin boundaries inside PSPs. It is due to this fact such objects are also designated as multiple-twinned particles [2][3][4][5][6].Small metal particles including multiple-twinned ones can be fabricated by various techniques, in particular, by nucleation from a gas phase with the use of physical or chemical vapor deposition onto a substrate [1]. Electrodeposition from an electrolyte solution plays an important role among the methods of fabrication of metal microparticles. This simple technique demonstrates a big variety of the control parameters such as electrolyte chemical composition, electric current density, cathode overvoltage, deposition time, process temperature, and the type of substrate. For example, variation in the chemical composition of the electrolyte, but for the same deposited metal, leads to considerable changes in the structure of the fabricated objects [7].In the present work, we investigate the effect of electrolyte pH on the morphology of the electrodeposited small silver particles and microcrystals and describe atypical shapes of silver PSPs.To fabricate silver small particles and microcrystals, we used a solution prepared with a distilled water and containing 35 g/l of silver nitrate AgNO 3 and 150 g/l of ammonium sulfate (NH 4 ) 2 SO 4 . The control parameter was electrolyte рН varied from 4.0 to 10.0 by adding a 25-percent aqueous solution of ammonia NH 4 OH. For reproducibility of experimental results, deposition of silver was carried out in a potentiostatic regime with cathode overvoltage of 100 . . . 1...

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This paper evaluates the fatigue strength of ultrafine-grained (UFG) Grade 4 Ti in the low-cycle fatigue region, as well as the strength of medical implants (plates and screws) made of UFG Ti under various types of loading in comparison with the strength of products made of coarse-grained (CG) Ti. To produce a UFG state, titanium billets after annealing were processed by the ECAP-Conform technique. The fatigue of the prismatic specimens with a thickness of 10 mm from CG and UFG Ti was tested by the three-point bending method using an Instron 8802 facility. The modeling and evaluation of the stress-strain state in the ANSYS software package for finite-element analysis revealed, in particular, the localization of equivalent stresses in the area of hole edges and at fillets during the tension of the plates. The performed research has demonstrated that medical implants (plates and screws) from UFG Grade 4 Ti have a higher strength under different types of loading (tension, fatigue strength, torsion) in comparison with products from CG Ti. This opens up a possibility for the miniaturization of medical products from UFG Ti while preserving their main performance properties at an acceptable level.

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