Preparation and characterization of Ti–Ta alloys for application in corrosive media

doi:10.1016/S0167-577X(02)01422-2

Materials Letters

Volume 57, Issue 20, June 2003, Pages 3010-3016

https://doi.org/10.1016/S0167-577X(02)01422-2 Get rights and content

Abstract

Titanium (Ti) exhibits a good corrosion resistance in oxidizing acids and neutral media but is severely attacked in reducing acids. On the contrary, tantalum (Ta) presents an excellent resistance in both oxidizing and reducing acids, but its high cost limits its use to very aggressive conditions. The Ti–Ta alloys are promising materials for use in reducing acids, due to their lower cost and density when compared to tantalum, and their higher corrosion resistance when compared to titanium. Ti-20, 40, 60 and 80 wt.% Ta alloys were prepared by arc melting and were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffractometry (XRD). Some electrochemical experiments were performed in H₂SO₄ solutions at room temperature to evaluate their corrosion resistance.

Introduction

Pure titanium (Ti) offers outstanding corrosion resistance in a wide variety of environments, specially oxidizing, neutral and inhibited reducing media [1]. The corrosion resistance of Ti is due to the formation of a protective and self-adherent oxide film mainly composed of TiO₂ [2]. For this reason, Ti is widely used for handling nitric acid in industrial applications and marine environments [3]. Nevertheless, Ti is severely attacked in reducing acids [1], except when oxidizing species such as oxygen, ferric, cupric and chromic ions are present [4].

Tantalum (Ta) exhibits an excellent corrosion resistance in almost all aqueous media except HF and alkaline solutions [5]. Its main application is found in equipments for chemical industry dealing with hot and concentrated mineral-reducing acids such as H₂SO₄ e HCl, where the usual structural alloys do not resist [6], [7]. Its high resistance is due to the formation of a protective Ta₂O₅ oxide film. It is not more widely used in chemical environments due to its high cost, nearly 10 and 5 times the cost of stainless steel and Ti for finished fabricated equipment, respectively [8].

Ti–Ta alloys are promising materials for substitution of Ta because they save weight and cost when compared to Ta and are expected to present higher corrosion resistance than Ti in reducing acids. Despite these advantages, few works are available about Ti–Ta alloys and their corrosion resistance [9], [10], [11]. Especially, no data are available on their electrochemical behavior in reducing acid solutions.

In this work, Ti-20, 40, 60 and 80 wt.% Ta alloys were obtained by arc melting, with and without subsequent heat treatment, and characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffractometry (XRD). The microhardness and density of the alloys were also measured. Some preliminary electrochemical experiments were performed to evaluate the corrosion behavior of the Ti–Ta alloys in 80 wt.% H₂SO₄ solutions at room temperature.

Section snippets

Experimental procedure

Ti and Ta shapes were mixed in the appropriate proportions to obtain the Ti-20, 40, 60 and 80 wt.% Ta alloys. The pure metals were previously degreased and pickled in 4HNO₃+1HF (v/v) solution for Ti and 2HNO₃+2HF+5H₂SO₄+2H₂O (v/v) solution for Ta. The mixtures were arc melted under argon atmosphere of 99.9% purity. After the first melting, samples were cut from the ingots, mounted in resin, grounded until 4000 grit and polished using an aqueous suspension of Al₂O₃ powder. The remaining

Preparation and characterization of the Ti–Ta alloys

After the first melting, two important observations were made from MEV observations: (1) an incomplete fusion of the Ta shapes occurred and (2) a great segregation took place during solidification. Difficulties for the obtainment of Ti–Ta alloys by conventional arc melting have been reported [12]. These difficulties arise from the great difference between the melting point and density of both Ti and Ta (Table 1) and the relatively large two-phase (liquid+solid) field in the binary Ti–Ta phase

Conclusions

The Ti-20, 40, 60 and 80 wt.% Ta alloys were produced by arc melting followed by heat treatment at 1200 °C for 48 h and cooling to room temperature in the furnace.

Both α- and β-phases were detected in the microstructure of Ti–20Ta and Ti–40Ta alloys, whereas only the β-phase was present in Ti–60Ta and Ti–80Ta alloys.

The microhardness of these alloys was higher than those of Ti and Ta.

From a preliminary electrochemical study in 80 wt.% H₂SO₄ solutions at room temperature, Ti–20Ta was shown to be

Acknowledgments

K.A.S. and A.R. acknowledge the Fundação de Amparo à Pesquisa do Estado de São Paulo—Brazil (FAPESP) for financial support (proc. 01/06974-0 and 00/13707-5).

References (15)

R.W. Schutz et al.
Effect of oxide films on the corrosion resistance of titanium
Corrosion
(1981)
G. Bewer et al.
Titanium for electrochemical processes
Journal of Metals
(1982)
H.B. Bomberger
Factors which influence corrosion properties of titanium
M. Schussler et al.
Corrosion of tantalum
R.H. Burns et al.
Industrial applications of corrosion-resistant tantalum, niobium and their alloys
C.E.D. Rowe
Fabrication of a tantalum structure for chemical plant use
Metal Construction
(1984)

There are more references available in the full text version of this article.

Cited by (50)

Improving biocompatibility for next generation of metallic implants
2023, Progress in Materials Science
The increasing need for joint replacement surgeries, musculoskeletal repairs, and orthodontics worldwide prompts emerging technologies to evolve with healthcare's changing landscape. Metallic orthopaedic materials have a shared application history with the aerospace industry, making them only partly efficient in the biomedical domain. However, suitability of metallic materials in bone tissue replacements and regenerative therapies remains unchallenged due to their superior mechanical properties, eventhough they are not perfectly biocompatible. Therefore, exploring ways to improve biocompatibility is the most critical step toward designing the next generation of metallic biomaterials. This review discusses methods of improving biocompatibility of metals used in biomedical devices using surface modification, bulk modification, and incorporation of biologics. Our investigation spans multiple length scales, from bulk metals to the effect of microporosities, surface nanoarchitecture, and biomolecules such as DNA incorporation for enhanced biological response in metallic materials. We examine recent technologies such as 3D printing in alloy design and storing surface charge on nanoarchitecture surfaces, metal-on-metal, and ceramic-on-metal coatings to present a coherent and comprehensive understanding of the subject. Finally, we consider the advantages and challenges of metallic biomaterials and identify future directions.
Strengthening mechanism of lamellar-structured Ti-Ta alloys prepared by powder metallurgy
2022, Journal of Materials Research and Technology
Titanium-tantalum alloys with lamellar microstructure were fabricated by cold isostatic pressing under 400 MPa and pressure-free sintering at 1600 °C. By such a low-cost powder metallurgy method, the Ti–Ta alloy exhibited the tensile yield strength of 1124 MPa at room temperature, which was twice that of the cast Ti–Ta alloys. The microstructure and mechanical properties were characterized in detail to elucidate the deformation behavior and the strengthening mechanism of the Ti–Ta alloys prepared by powder metallurgy. With the increasing Ta content, the width of the α laths decreased, and that of the β laths increased, leading to the precipitation of the acicular α in the β laths. Correspondingly, the yield and ultimate strength increased, while the strain to failure decreased. Lamellar structure strengthening was determined to be the dominating mechanism for the high strength of the Ti–Ta alloys prepared by powder metallurgy. After quantitatively evaluating the contributions of laths, solute atoms, prior β grain boundaries, and dislocations, a model was established to illustrate the yield strength of the Ti–Ta alloys. The calculated values agreed well with the measured strength values of the Ti–Ta alloys, indicating that this model is effective in forecasting the strength of the dual-phase Ti alloys with lamellar structure.
Ti–Ta dental alloys and a way to improve gingival aesthethic in contact with the implant
2022, Materials Chemistry and Physics
The development of Ti-based alloys with improved properties for medical applications is a challenge nowadays in the field of materials engineering. In this study, the color of oxide layers developed by anodic oxidation in H₂SO₄ solution on Ti–Ta alloys was studied and the alteration in microhardness was evaluated. The alloys were manufactured by levitation fusion technique using Ti as base material and Ta was added in 5, 15, 25, and 30 wt%. After the alloys were passivated, changes of oxide color function of applied potential, the growth of oxide mass and the microhardness were investigated. The studies showed that the oxide mass increases with the potential and the hardness values vary as a function of Ta addition. The microhardness results showed that the oxide layer developed after passivation on the surface of Ti–25Ta alloy exhibited higher hardness values and a denser oxide layer as compared to the Ti–5Ta, Ti–15Ta, and Ti–30Ta alloys. Using a potential of 70 V a redish oxide color was obtained which might have optimal aplications in dentistry due to its aesthetics and mechanical properties.
Relationship between microstructure, phase transformation, and mechanical behavior in Ti–40Ta alloys for biomedical applications
2021, Journal of Materials Research and Technology
Citation Excerpt :
Since the use of toxic and harmful elements should be avoided in the next generation of orthopedic biomaterials with enhanced biomechanical performance and durability, the tantalum arises as one the most biocompatible alloying elements to titanium. Also, tantalum addition is known to impart extremely high corrosion resistance to Ti alloys [21,22]. The interest in Ti–Ta alloys has grown due to their high strength-to-density ratio [23].
Titanium and Ti alloys are important materials for scientific and technological applications, especially as biomaterials, due to their excellent corrosion resistance, biocompatibility, and mechanical properties. In this work, the influence of tantalum on the microstructure and mechanical properties of Ti–40Ta alloys were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and mechanical spectroscopy (MS) techniques. XRD and SEM analyses showed that commercially pure (CP) Ti consists of a single α-phase (hcp) with an equiaxed morphology, while Ti–40Ta alloy consists of α" (orthorhombic) and β (bcc) phases. The anelastic relaxation spectra of Ti–40Ta alloy presented characteristics combining CP Ti and pure Ta anelastic responses, where the complex anelastic relaxation peaks observed around 575 and 680 K could be resolved into matrix-interstitial and substitutional-interstitial components, corresponding to Ta–O, Ti–O, and Ta–N single interactions. The combination of thermal cycles and applied stress during the mechanical spectroscopy characterization of Ti–40Ta alloy promotes the α" → β phase transition until β phase stabilization. From flexural vibration measurements, the elastic modulus values at room temperature were: (102 ± 9) GPa for CP Ti and (71 ± 5) GPa for the Ti–40Ta alloy. These results provide a valuable contribution to a better understanding of the structure and mechanical properties of the Ti–40Ta alloy, thus allowing the optimization of its properties through thermal treatments, aiming at its potential application as a biomaterial for structural orthopedic applications.
Modeling and experimental validation of additively manufactured tantalum-titanium bimetallic interfaces
2021, Materials and Design
Bimetallic structures processed via laser-based additive manufacturing (AM) efficiently combine multiple materials in single components, which are difficult to achieve using traditional methods. However, limited understanding exists on how processing parameters influence the resulting microstructures and thermal profiles of base material during processing, affecting component performance. To this end, we present a combined numerical and experimental study on the effects of input laser power and scanning speed on the heat-affected-zone (HAZ) and fusion-zone (FZ) of a tantalum-titanium bimetallic structure, two compatible materials that are challenging to process traditionally and are desirable in a bimetallic system. We demonstrate that a wide array of track characteristics can be achieved by varying the laser power and scanning speed. The HAZ and FZ microstructures' width and depth within the underlying Ti6Al4V substrate can be estimated within 6–19% of the experimentally determined values using a 3D transient-thermal finite element analysis (FEA) model, with the most significant errors occurring at low scanning speeds. Adjusting the absorptivity input to the model improves prediction to within 1–11% difference of the HAZ/FZ dimensions and corresponding temperatures relative to the experimental dimensions across a broad range of laser power and scanning speeds. Our results indicate that the underlying temperatures achieved in bimetallic components can be predicted accurately using a detailed FEA approach, aiding larger-scale approaches towards improved process modeling and manufacturing of bimetallic structures using laser-based AM.
Improving the mechanical strength of ternary beta titanium alloy (Ti-Ta-Sn) foams, using a bimodal microstructure
2020, Materials and Design
Citation Excerpt :
Ti–Ta binary alloys have attracted a great interest due to their excellent combination of having high strength, a relative low modulus, and a corrosion resistance that is superior to that of pure Ti [23]. Nevertheless, there are few reports concerning Ti–Ta alloys [24–27] and even fewer works that analyze the effect of Sn addition on the microstructure and properties of Ti–Ta alloys. From a biocompatibility's point of view, pure Ta and Sn are interesting elements, since they are classed as highly biocompatible due to them exhibiting negligible effects on the human body [28].
The effects of a bimodal microstructure and porosity on the elastic modulus and yield strength of a Ti-13Ta-12Sn alloy foam was analyzed. In order to obtain a bimodal microstructure, the powder metallurgy approach was used, with the amount of Sn being chosen depending on a thermodynamic analysis, so that there could be a bcc solid solution after the consolidation process. The foams were obtained using an ammonium carbonate space holder (30, 40 and 50 v/v% porosity). Foams with a bimodal microstructure were synthetized by mixing 50 wt% of milled powder (at 50 h) + 50 wt% unmilled powder, while foam without a bimodal microstructure were synthetized using only milled powders. The elastic modulus and compression yield strength were experimentally measured and compared with estimations given by the Gibson-Ashby model and finite element analysis. The foams with a bimodal microstructure have shown a higher compression strength (over 70 MPa more) than the samples without bimodal microstructure, for all of the porosity values. The samples with bimodal microstructures, as well as 30, 40 and 50% porosity, have an elastic modulus smaller than 30 GPa and a yield strength over 120 MPa, therefore, having a great potential to be explored for biomedical applications.

View all citing articles on Scopus

View full text

Preparation and characterization of Ti–Ta alloys for application in corrosive media

Abstract

Introduction

Section snippets

Experimental procedure

Preparation and characterization of the Ti–Ta alloys

Conclusions

Acknowledgments

Effect of oxide films on the corrosion resistance of titanium

Corrosion

Titanium for electrochemical processes

Journal of Metals

Factors which influence corrosion properties of titanium

Corrosion of tantalum

Industrial applications of corrosion-resistant tantalum, niobium and their alloys

Fabrication of a tantalum structure for chemical plant use

Metal Construction