Reducing the stiffness of titanium is an important issue to improve the behavior of this material when working together with bone, which can be achieved by generating a porous structure. The aim of this research was to analyze the porosity and mechanical behavior of Ti–6Al–4V porous samples developed by spherical powder sintering. Four different microsphere sizes were sintered at temperatures ranging from 1300 to 1400 °C for 2, 4 and 8 h. An open, interconnected porosity was obtained, with mean pore sizes ranging from 54.6 to 140 µm. The stiffness of the samples diminished by as much as 40% when compared to that of solid material and the mechanical properties were affected mainly by powder particles size. Bending strengths ranging from 48 to 320 MPa and compressive strengths from 51 to 255 MPa were obtained.
The use of boron for successfully obtaining high density PM stainless steels with improved mechanical properties and corrosion resistance is presented. Boron is added as part of master alloys which have been specifically designed to provide the formation of wetting liquid phases with excellent characteristics for producing controlled densification and alloying of 316L and 304L austenitic stainless steels. The as-sintered density and properties of these alloys is determined by the amount of master alloy, the chemical composition of the stainless steel powder, the sintering temperature and time. The microstructural development and alloy homogenisation are determined by the chemical composition of the Fe-based powder and the chemical reactions taking place between the basic powder and the master alloy particles during high temperature sintering. The use of this master alloy is shown to lead to stainless steels with outstanding combinations of strength and ductility. The influence of alloying and the sintering conditions on the final microstructure, density, corrosion resistance and tensile properties is also discussed.
ResumenEl titanio es un material biocompatible que, además de presentar buenas propiedades a la corrosión, posee una elevada resistencia mecánica teniendo en cuenta su baja densidad. En el campo de la pulvimetalurgia, entre otras aplicaciones, este material se usa con objeto de obtener materiales porosos para aplicaciones biomédicas. Recientemente se ha investigado la aplicación de los materiales porosos en la fabricación de implantes de cadera. La razón principal está basada en la reducción de la rigidez de los implantes, lo cual minimiza los efectos del "apantallamiento de tensiones", al aproximarse su módulo elástico al del hueso. El propósito del presente trabajo, es producir materiales porosos mediante la técnica de sinterización con espaciador, usando el bicarbonato de amonio como propulsor de la formación de poros. Para la obtención de los mismos, se ha utilizado polvo de titanio de diferentes tamaños de partícula, usando diversas presiones de compactación. Antes de realizar la sinterización, se han evaluado las propiedades mecánicas de las muestras en verde, de modo que se permita su manipulación. Tras realizar la sinterización, se ha evaluado la densidad y porosidad. Igualmente, se ha valorado el efecto de estas variables en las propiedades mecánicas y el módulo elástico, obtenidos mediante el ensayo de flexión a tres puntos. La caracterización microestructural se ha realizado mediante microscopía óptica y electrónica. Palabras claveTitanio poroso; Rigidez; Método del espaciador; Bicarbonato de amonio; Tamaño de partícula; Ensayo de flexión. Fabrication and characterisation of porous Ti and Ti6Al4V produced by sintering with spacer AbstractTitanium is well-known to be a biocompatible material with good corrosion properties and good strength, taking into account their low specific weight. In powder metallurgy field, titanium has been used in order to obtain porosity materials for biomedical applications. Recently, porous materials have been investigated for their use like hips implants. The principal reason is based on a reduction of stiffness implants, minimizing effects of stress shielding. The purpose of the present work is produced porous materials by space holder technique using ammonium bicarbonate like spacer. Scaffolds of titanium have been fabricated by powders of titanium with different grades of particle size and compacting pressure. Before sintering, stability of green parts has been studied by mechanical test. After sintering, porosity has been evaluated besides mechanical properties and elastic modulus by three points bending test. The microstructural characterisation is performed by optical and electron microscopy.
Titanium is a material used in biomedicine for osseous implants due to their low density and biocompatibility. Its use in this field is limited by the lack of similarity of their stiffness with the stiffness of bones. In order to reduce this difference, powder metallurgy offers ways to develop porous materials with a reduced stiffness. The main objective of this work is to develop titanium scaffolds by space-holder technique, concretely with using two different spacers: Ammonium bicarbonate and sodium chloride. It has been studied the best way for remove spacer of green compacts, which have been sintered in high vacuum. Materials obtained by using of two spacers, have been analyzed in order to value different results in porosity, microstructural and mechanical properties. The stiffness of new materials was obtained by testing of three points in bending. This research shows that the manufacturing method of porous materials for bone replacement using space holder technique with ammonium bicarbonate or sodium chloride, allows obtained samples with slightly difference in physical, microstructural and mechanical properties.
Being an effective sintering enhancer boron is gaining relevance for obtaining high density PM steels. Thermodynamic calculations are an important tool for studying the roll of alloying elements in the formation of a liquid during sintering. In the present work, the system Fe-Cr-B was obtained by combining up to date thermodynamic descriptions for the subsystems Fe-Cr, Cr-B and B-Cr. The calculations were carried out with Thermo-Calc software to predict isothermal sections for the ternary diagram for 1210 and 1250°C. The analysis of the isothermal sections indicates that the solid phases in equilibrium with the liquid are M2B and a-BCC solid solution. The generation of the liquid is based on a eutectic reaction (Lða+(FeCr)2B) involving the mixed borides previously formed. On the other hand, simulations for PM steels with constant boron but higher chromium content allowed realising that the formation of the liquid may be completely inhibited, within the temperature range under consideration, as materials with too high Cr/Fe ratios are used. This study was also supported by selected experiments which were in excellent agreement with the thermodynamic calculations.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.