Papers by Author: Doina Raducanu

Abstract: In recent years a significant increase in new Ti-based biocompatible alloys (such as TiTaZr or TiTa-Nb-Zr) development was reported. Titanium and its alloys have been widely used in medicine since the 1960s because of their known biocompatibility, superior mechanical properties, low density and remarkable chemical stability. The present study investigates the microstructures and the mechanical properties of a Ti-29Nb-9Ta-10Zr (wt.%) alloys in order to investigate structural changes occurred during recrystallization treatment of 90% cold rolled Ti-29Nb-9Ta-10Zr (wt.%) alloy. The investigated alloy was fabricated by vacuum arc induction melting in levitation, using a FIVES CELES MP 25 furnace, starting from elemental components. Structural changes occurred during recrystallization treatment were investigated using X-ray diffraction, using a Philip PW 3710 diffractometer, in Bragg-Brentano θ-2θ geometry, with negligible instrumental broadening. Data concerning alloys component phases, average coherent crystallite size and internal average micro-strain was obtained.

Abstract: During the last decade the titanium alloys were extensively used in a variety of applications due to their good mechanical properties, high biocompatibility and corrosion resistance. β-type Ti alloys composed of Nb, Ta and Zr elements have received much attention, because they feature high specific strength, bio-corrosion resistance, no allergic problems and biocompatibility. A Ti-29Nb-9Ta-10Zr (wt.%) alloy was subjected to thermo-mechanical processing and testing. Two states were investigated: recrystallized and 80% cold-rolled. Data concerning phase structure and developed texture, expressed by Inverse Pole Figures (IPFs) and Orientation Distribution Functions (ODFs), was obtained and analyzed.

Abstract: A Ti-25Ta-25Nb β-type titanium alloy was subjected to thermo-mechanical processing and testing with the aim to observe the twinning deformation mechanism. Data concerning the evolution of twinning versus stress was obtained by SEM and micromechanical testing. Mechanical properties of the investigated alloy were also evaluated

Abstract: The design of novel Ti-based alloys for biomedical load-bearing implant application, such as hip or knee prostheses, aims at providing structural materials which are characterized by good corrosion stability in the human body, high fatigue resistance, high strength-to-weight ratio, good ductility, low elastic modulus, excellent wear resistance, low cytotoxicity and a negligible tendency to provoke allergic reactions. Low elastic modulus is required to be close to that of a human bone, in order to transfer the adequate mechanical stress to the surrounding bone. The Young’s modulus of biomaterials is desired to be equal to that of cortical bone because if the Young’s modulus of biomaterials is much greater than that of cortical bone, bone resorption occurs. Investigated samples were subjected to mechanical tests, having provided these mechanical properties: ultimate tensile strength (σ_UTS), yield strength (σ_YS), elongation to fracture (ε_f) and elastic modulus (E).

Abstract: The shape memory alloys are materials that can change their shape by applying thermomechanical treatments. In order to design SMA materials, the stress-strain-temperature relationship is necessary. Modeling the constitute behavior of these materials supposes a few phenomenological models that can provide a quick and reasonable approach to assess the behavior of SMA. The proposed constitutive equation expresses well the properties of the shape memory effect, pseudoelasticity and recovery stress.

Abstract: The paper is an electrochemical study regarding the influence of different acid etching conditions on the corrosion behaviour of a new Ti based bioalloy with Nb, Ta and Zr. Open circuit, potentiodynamic and electrochemical impedance spectroscopy were the methods performed in a simulated body fluid (SBF) and a stability mechanism was discussed in terms of equivalent circuits.