Fracture characteristics of titanium VT1-0 and Zr–1 wt. % Nb alloy in different structures under gigacycle fatigue loading regime

Fatigue testing of ultrafine-grained, fine-grained and coarse-grained VT1-0 and Zr–1 wt. % Nb samples was performed under conditions of gigacycle fatigue regime. It was established that ultrafine-grained titanium and zirconium alloy samples initiate increasing fatigue strength of up to 1.3 times for titanium and 1.7 times for zirconium alloy within gigacycle region (109 cycles) comparable to fine-grained and coarse-grained samples. Analysis of fracture surface morphology has revealed the similar fractured structure in coarse-grained and ultrafine-grained titanium and zirconium alloy samples. Fractures in ultrafine-grained titanium and zirconium alloy samples exhibit quasi-brittle pattern

Influence of Hydrothermal Processing on the Structuring of Amorphous Strontium Hydroxyapatite

Strontium substituted hydroxyapatite is a biomaterial with high level of biocompatibility with improved cell proliferation from Sr ions in hydroxyapatite. The aim of this research is to study the effect of saturated steam pressure at elevated temperature on the transitions within amorphous strontium hydroxyapatite powder. Processing temperatures and times ranged from 90 to 150∘C for periods of 1, 3 and 6 hours, respectively. Powder was characterized by X-Ray Diffraction and Fourier Transformed Infrared Spectroscopy. The appearance of diffraction peaks in the X-ray diffraction pattern suggested that longer processing times were necessary to transform amorphous strontium hydroxyapatite to a higher crystallinity at lower temperatures. Transition from the amorphous to the crystalline state begins at 150∘C after an hour, at 120∘C after 3 hours, or at 110∘C after 6 hours. Infrared spectroscopy showed the characteristic phosphate absorption band and the presence of carbonate in the powder.     Keywords: hydrothermal processing, biomaterials, hydroxyapatite, material design, biocompatibilit

Mechanism of improvement of TiN-coated tool life by nitrogen implantation

The life of TiN-coated tools can be improved by a post-coating ion implantation treatment, but the mechanism by which this occurs is still not clear. Nitrogen implantation of both physical-vapor-deposited TiN and CVD TiN leads to surface softening as the dose increases, which has been attributed to amorphization. In this study a combination of transmission electron microscopy and atomic force microscopy was used to characterize the microstructure of implanted TiN coatings on cemented carbide for comparison with mechanical property measurements (nanoindentation, residual stress, etc.), made on the same samples. Ion implantation leads to a slight reduction in the grain size of the TiN in the implanted zone, but there is no evidence for amorphization. Surface softening is observed for physical-vapor-deposited TiN, but this is probably due to a combination of changes in surface composition and the presence of a layer of bubbles generated by the very high implantation doses use

Effect of grain refinement on deformation behavior of technical grade titanium under tension

The paper deals with the study on the impact of grain refinement by severe plastic deformation upon the microstructure, as well as deformation and fracture behavior under tensile loading of technical grade titanium. The microstructure of coarse- and ultra-fine grain technical grade titanium was investigated by optical, transmission electron microscopy and X-ray diffraction. In situ monitoring of deformation behavior was conducted by means of acoustic emission and digital image correlation. Scanning electron microscopy was employed for fracture surface observation. The results of the tensile tests have revealed significant growth in ultimate strength and decrease of ductility due to grain-boundary strengthening. The experimental data obtained allow one to get the appropriate understanding of the mechanisms responsible for variation of mechanical properties and fracture patterns as well as to attain quantitative estimation of strain localization induced by the grain refinement

Phase Composition and Microstructure of Ti-Nb Alloy Produced by Selective Laser Melting

The phase composition and microstructure of Ti-Nb alloy produced from composite titanium and niobium powder by selective laser melting (SLM) was studied. Produced monolayered Ti-Nb alloy enhanced the formation of fine-grained and medium-grained zones with homogeneous element composition of 36-38% Nb mass interval. Alloy phase composition responded to [beta]-alloy substrate phase (grain size was 5-7 pm) and non-equilibrium martensite [alpha]"- phase (grain size was 0.1-0.7 [mu]m). [alpha]"-phase grains were found along [beta]-phase grain boundaries and inside grains, including decreased niobium content. Alloy microhardness varied within 4200-5500 MPa

СВОЙСТВА ДЕМИНЕРАЛИЗОВАННОГО КОСТНОГО МАТРИКСА ДЛЯ БИОИНЖЕНЕРИИ ТКАНЕЙ

The purpose. Determination of tissues of physico-mechanical properties of demineralized bone matrix of spongy and compact human bone important for bioengineering.Material and Methods.The methods for studying micromorphological, piezoelectric and transport properties, adapted for measuring the materials of potential scaffolds.Results. The results of studying the physico-mechanical properties of the demineralized bone matrix of spongy and compact human bones are presented. It is shown that the demineralized spongy bone possesses the best characteristics of the pore system for the colonization of matrix cells. The tensile strength and modulus of elasticity of samples from the demineralized heads of the femurs extracted during the initial hip arthroplasty vary widely. The modulus of elasticity varied from 50 to 250 MPa, and the ultimate strength was from 1.1 to 5.5 MPa.Conclusion. Methods for measuring micromorphological, piezoelectric and transport properties for materials of potential matrices were developed and / or adapted. It is shown that in the samples of materials from the human bone, these characteristics, as a rule, vary considerably. Proceeding from this, it becomes obvious that the development of protocols of measurement methods of the above listed properties is an important work for the creation of technology of bioengineering of tissue implants for reconstructive surgery. Цель. Определение значимых для биоинженерии тканей физико-механических свойств деминерализованного костного матрикса губчатой и компактной кости человека.Материалы и методы. Перечислены методы исследования микроморфологических, пьезоэлектрических и транспортных свойств, адаптированные для измерения у материалов потенциальных матриц.Результаты. Приведены результаты исследования физико-механических свойств деминерализованного костного матрикса губчатой и компактной кости человека. Показано, что деминерализованная губчатая кость обладает наилучшими характеристиками поровой системы для заселения матриксов клетками. Предел прочности и модуль упругости образцов из деминерализованных головок бедренных костей, извлеченных в ходе первичного эндопротезирования тазобедренного сустава, изменяются в широких пределах. Модуль упругости изменялся от 50 до 250 МПа, а предел прочности – от 1,1 до 5,5 МПа.Заключение. Были отработаны и/или адаптированы методы измерений микроморфологических, пьезоэлектрических и транспортных свойств у материалов потенциальных матриц. Показано, что у образцов материалов из кости человека данные характеристики, как правило, значительно варьируют. Исходя из этого, становится очевидным, что отработка протоколов методов измерения вышеперечисленных свойств является важной работой для создания технологии биоинженерии тканевых имплантатов для восстановительной хирургии.