Fatigue and stress rupture properties of Inconel 713C, V-57C and titanium alloys 7A1-3Mo-Ti and MST 821 (8A1-2Cb-1Ta-Ti)

"Materials Central, Contract No. AF 33(616)-6828, Project No. 7351."

Machining data for titanium alloys.

"AFMDC 65-1."

The relationship between fracture toughness and microstructure in titanium alloys

Linear Elastic Fracture Mechanics has been used to study the microstructural factors controlling the strength and toughness of two alpha-beta, titanium alloys. Fracture toughness was found to be independent of orientation for alloy Ti/6A1/4-V, but orientation dependent for IMI 700, bend and tension specimens giving similar toughness values. Increasing the solution temperature led to the usual inverse relationship between strength and toughness, with toughness becoming a minimum as the beta transus was approached. The production of a double heat treated microstructure led to a 100% increase in toughness in the high strength alloy and a 20% increase in alloy Ti/6A1/4V, with little decrease in strength. The double heat treated microstruoture was produced by cooling from the beta field into the alpha beta field, followed. by conventional solution treatment and ageing. Forging above the beta transus led to an increase in toughness over alpha beta forging in the high strength alloy, but had little effect on the toughness of Ti/6A1/4V. Light and electron microscopy showed that the increased toughness resulted from the alpha phase being changed from mainly continuous to a discontinuous platelet form in a transformed beta matrix. Void formation occurred at the alpha-beta interface and crack propagation was via the interface or across the platelet depending on which process required the least energy. Varying the solution treatment temperature produced a varying interplatelet spacing and platelet thickness. The finest interplatelet spacing was associated with the highest toughness, since a higher applied stress was required to give the necessary stress concentration to initiate void formation. The thickest alpha platelet size gave the highest toughness which could be interpreted in terms of Krafftt's "process zone size" and the critical crack tip displacement criterion by Hahn and Rosenfield from an analysis by Goodier and Field.

Growth of short fatigue cracks in titanium alloys

The initiation and early propagation of short fatigue cracks has been studied in detail in two alpha / beta titanium alloys as a function of microstructure. Detailed metallography is presented relating short crack growth rates to the microstructural features present. The work shows the significant differences in short crack propagation rates which can be achieved by microstructural changes within a single alloy.

Influence of the Substitutional Solute on the Mechanical Properties of Ti-Nb Binary Alloys for Biomedical Use

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Electrochemical stability and corrosion resistance of Ti-Mo alloys for biomedical applications

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Biomedical Ti-Mo Alloys with Surface Machined and Modified by Laser Beam: Biomechanical, Histological, and Histometric Analysis in Rabbits

Purpose: In vivo bone response was assessed by removal torque, hystological and histometrical analysis on a recently developed biomedical Ti-15Mo alloy, after surface modification by laser beam irradiation, installed in the tibia of rabbits. Materials and Methods: A total of 32 wide cylindrical Ti-15Mo dental implants were obtained (10mm × 3.75mm). The implants were divided into two groups: 1) control samples (Machined surface - MS) and 2) implants with their surface modified by Laser beam-irradiation (Test samples - LS). Six implants of each surface were used for removal torque test and 10 of each surface for histological and histometrical analysis. The implants were placed in the tibial metaphyses of rabbits. Results: Average removal torque was 51.5Ncm to MS and >90Ncm to LS. Bone-to-implant-contact percentage was significantly higher for LS implants both in the cortical and marrow regions. Conclusions: The present study demonstrated that laser treated Ti-15Mo alloys are promising materials for biomedical application. © 2011 Wiley Periodicals, Inc.

Titanium-35niobium alloy as a potential material for biomedical implants: in vitro study

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Structure, microstructure, and selected mechanical properties of Ti-Zr-Mo alloys for biomedical applications

New titanium alloys for biomedical applications have been developed primarily with the addition of Nb, Ta, Mo, and Zr, because those elements stabilize the β phase and they don’t cause cytotoxicity in the organism. The objective of this paper is to analyze the effect of molybdenum on the structure, microstructure, and selected mechanical properties of Ti-15Zr-xMo (x = 5, 10, 15, and 20 wt%) alloys. The samples were produced in an arc-melting furnace with inert argon atmosphere, and they were hot-rolled and homogenized. The samples were characterized using chemical, structural, and microstructural analysis. The mechanical analysis was made using Vickers microhardness and Young’s modulus measurements. The compositions of the alloys were sensitive to the molybdenum concentration, indicating the presence of α’+α”+β phases in the Ti-15Zr-5Mo alloy, α”+β in the Ti-15Zr-10Mo alloy, and β phase in the Ti-15Zr-15Mo and Ti-15Zr-20Mo alloys. The mechanical properties showed favorable values for biomedical application in the alloys presenting high hardness and low Young’s modulus compared with CP-Ti.

The influence of heat treatment on the structure and microstructure of Ti-15Mo-xNb system alloys for biomedical applications

The Ti-15Mo-xNb system integrates a new class of titanium alloys without the presence of aluminum and vanadium, which exhibit cytotoxicity, and that have low elasticity modulus values (below 100 GPa). This occurs because these alloys have a beta structure, which is very attractive for use as biomaterials. In addition, Brazil has about 90% of the world’s resources of niobium, which is very important economically. It strategically invests in research on the development and processing of alloys containing this element. In this paper, a study of the influence of heat treatments on the structure and microstructure of the alloys of a Ti-15Mo-xNb system is presented. The results showed grain grown with heat treatment and elongated and irregular grains after lamination due to this processing. After quenching, there were no changes in the microstructure in relation to heat-treated and laminated conditions. These results corroborate the x-ray diffraction results, which showed the predominance of the β phase.

Characterization of a new beta titanium alloy, Ti-12Mo-3Nb, for biomedical applications

In recent years, different beta titanium alloys have been developed for biomedical applications with a combination of mechanical properties including a low Young's modulus, high strength, fatigue resistance and good ductility with excellent corrosion resistance. From this perspective, a new metastable beta titanium Ti-12Mo-3Nb alloy was developed with the replacement of both vanadium and aluminum from the traditional Ti-6Al-4V alloy. This paper presents the microstructure, mechanical properties and corrosion resistance of the Ti-12Mo-3Nb alloy heat-treated at 950 degrees C for 1 h. The material was characterized by X-ray diffraction and by scanning electron microscopy. Tensile tests were carried out at room temperature. Corrosion tests were performed using Ringer's solution at 25 degrees C. The results showed that this alloy could potentially be used for biomedical purposes due to its good mechanical properties and spontaneous passivation. (c) 2011 Elsevier B.V. All rights reserved.

Influence of the substitutional solute on the mechanical properties of Ti-Nb binary alloys for biomedical use

Titanium alloys are widely used in the manufacture of biomedical implants because they possess an excellent combination of physical properties and outstanding biocompatibility. Today, the most widely used alloy is Ti-6Al-4V, but some studies have reported adverse effects with the long-term presence of Al and V in the body, without mentioning that the elasticity modulus value of this alloy is far superior to the bone. Thus, there is a need to develop new Ti-based alloys without Al and V that have a lower modulus, greater biocompatibility, and similar mechanical strength. In this paper, we investigated the effect of Nb as a substitutional solute on the mechanical properties of Ti-Nb alloys, prepared in an arc-melting furnace and characterized by density, X-ray diffraction, optical microscopy, hardness and elasticity modulus measurements. The X-ray and microscopy measurements show a predominance of the α phase. The microhardness values showed a tendency to increase with the concentration of niobium in the alloy. Regarding the elasticity modulus, it was observed a nonlinear behavior with respect to the concentration of niobium. This behavior is associated with the presence of the α phase.

Effect of shotpeening on sliding wear and tensile behavior of titanium implant alloys

Titanium has good biocompatibility and so its alloys are used as implant materials, but they suffer from having poor wear resistance. This research aims to improve the wear resistance and the tensile strength of titanium alloys potentially for implant applications. Titanium alloys Ti–6Al–4V and Ti–6Al–7Nb were subjected to shotpeening process to study the wear and tensile behavior. An improvement in the wear resistance has been achieved due to surface hardening of these alloys by the process of shotpeening. Surface microhardness of shotpeened Ti–6Al–4V and Ti–6Al–7Nb alloys has increased by 113 and 58 HV(0.5), respectively. After shotpeening, ultimate tensile strength of Ti–6Al–4V increased from 1000 MPa to 1150 MPa, higher than improvement obtained for heat treated titanium specimens. The results confirm that shotpeening pre-treatment improved tensile and sliding wear behavior of Ti–6Al–4V and Ti–6Al–7Nb alloys. In addition, shotpeening increased surface roughness.