Special Issue "Powder Metallurgy of Titanium Alloys"

A special issue of Metals (ISSN 2075-4701).

Deadline for manuscript submissions: 31 March 2020.

Special Issue Editor

Prof. Dr. Elena Gordo
E-Mail Website
Guest Editor
Department of Materials Science and Engineering, Universidad Carlos III de Madrid, Madrid, Spain
Interests: powder metallurgy; titanium alloys; metal-ceramic composites; surface treatments; additive manufacturing

Special Issue Information

Dear Colleagues,

The production of titanium (Ti) components by powder metallurgy (PM) is nowadays a recognized cost-effective alternative to the casting and wrought processing route. The success in obtaining high performance/cost ratios relies on multiple factors, such as remaining porosity, interstitial elements, grain size or microstructural homogeneity. Intense research is under development in the field of Ti PM all over the world, from powder production to the latest advances in additive manufacturing. PM techniques are not only interesting due to the potential lower cost provided but also due to the high versatility in the design and production of new alloys that could widen the applications to alternative industrial sectors.

This Special Issue intends to cover the most innovative topics and strategies currently followed in PM Ti that will include fabrication of powders, alloying design, powder processing by cold or hot pressing, thermomechanical processing, fast techniques, direct additive manufacturing in all the variants (powder bed, wire, laser cladding), post processing, heat treatments, composites, porous materials, coatings and functionally graded materials (FGM). Special attention will be paid on the control of microstructure and its relation with properties in particular fatigue studies, oxidation, corrosion and wear behavior.

Prof. Dr. Elena Gordo
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Metals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • New titanium alloys
  • Powder production
  • Pressing and sintering
  • Additive manufacturing: direct techniques
  • Post-processing: heat treatments, surface treatments and coatings
  • Ti composites
  • Porous titanium
  • Mechanical properties
  • Fatigue behaviour
  • Oxidation and corrosion
  • Wear behaviour
  • High temperature applications
  • New applications

Published Papers (6 papers)

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Research

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Open AccessFeature PaperArticle
Oxidation and Corrosion Behavior of New Low-Cost Ti-7Fe-3Al and Ti-7Fe-5Cr Alloys from Titanium Hydride Powders
Metals 2020, 10(2), 254; https://doi.org/10.3390/met10020254 - 14 Feb 2020
Abstract
High production costs of Ti alloys usually hinders their use in industry sectors like the automotive and hence, low-cost titanium alloys could broaden titanium alloy usage. This work presents the study of three alloys— Ti-Fe, Ti-Fe-Al, and Ti-Fe-Cr—produced by powder metallurgy methods. The [...] Read more.
High production costs of Ti alloys usually hinders their use in industry sectors like the automotive and hence, low-cost titanium alloys could broaden titanium alloy usage. This work presents the study of three alloys— Ti-Fe, Ti-Fe-Al, and Ti-Fe-Cr—produced by powder metallurgy methods. The design of the compositions was aimed at reducing cost and enhance the oxidation and corrosion resistance while not decreasing the mechanical performance. The use of titanium hydride as raw material instead of Ti powder is highlighted as a key feature in the design and manufacturing procedure of the alloys. Introducing a dehydrogenation process during sintering favors the densification process while reducing the oxygen contamination and the production cost. There is a lack of studies focused on the implementation of affordable PM Ti alloys in high demanding environments. Therefore, a study of high temperature oxidation resistance and electrochemical behavior was performed. Full article
(This article belongs to the Special Issue Powder Metallurgy of Titanium Alloys)
Open AccessArticle
Microstructure and Mechanical Properties of Ti6Al4V Alloy Consolidated by Different Sintering Techniques
Metals 2019, 9(10), 1033; https://doi.org/10.3390/met9101033 - 23 Sep 2019
Abstract
In this paper, we investigated the effect of the different sintering techniques including vacuum sintering, capsule-free hot isostatic pressing (HIP), and capsule HIP on the microstructure and mechanical properties of Ti6Al4V alloy. The obtained results indicated that full density Ti6Al4V alloy could be [...] Read more.
In this paper, we investigated the effect of the different sintering techniques including vacuum sintering, capsule-free hot isostatic pressing (HIP), and capsule HIP on the microstructure and mechanical properties of Ti6Al4V alloy. The obtained results indicated that full density Ti6Al4V alloy could be obtained by using capsule HIP technique. The alloy sintered by capsule HIP had the highest hardness (~405 HV) and compressive yield strength (~1056 MPa). It is interesting that the geometry has a significant influence on the relative density and mechanical properties of the alloy sintered by the capsule-free HIP. The relative density, hardness, and compressive yield strength rise from center to periphery of the specimen. This is attributed to the heating and pressing in the capsule-free, which are external, leading to the densification processes starting from the outside to the inner parts of the pressed specimen. Using theoretical prediction with Gibson and Ashby power law found that the yield strength of the alloy sintered by capsule-HIP technique is much lower than that of the calculated value due to the formation of the coarse lamellar microstructure of α-Ti grains. Full article
(This article belongs to the Special Issue Powder Metallurgy of Titanium Alloys)
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Open AccessArticle
Porous Titanium Surfaces to Control Bacteria Growth: Mechanical Properties and Sulfonated Polyetheretherketone Coatings as Antibiofouling Approaches
Metals 2019, 9(9), 995; https://doi.org/10.3390/met9090995 - 10 Sep 2019
Abstract
Here, titanium porous substrates were fabricated by a space holder technique. The relationship between microstructural characteristics (pore equivalent diameter, mean free-path between pores, roughness and contact surface), mechanical properties (Young’s modulus, yield strength and dynamic micro-hardness) and bacterial behavior are discussed. The bacterial [...] Read more.
Here, titanium porous substrates were fabricated by a space holder technique. The relationship between microstructural characteristics (pore equivalent diameter, mean free-path between pores, roughness and contact surface), mechanical properties (Young’s modulus, yield strength and dynamic micro-hardness) and bacterial behavior are discussed. The bacterial strains evaluated are often found on dental implants: Methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa. The colony-forming units increased with the size of the spacer for both types of studied strains. An antibiofouling synthetic coating based on a sulfonated polyetheretherketone polymer revealed an effective chemical surface modification for inhibiting MRSA adhesion and growth. These findings collectively suggest that porous titanium implants designed with a pore size of 100–200 µm can be considered most suitable, assuring the best biomechanical and bifunctional anti-bacterial properties. Full article
(This article belongs to the Special Issue Powder Metallurgy of Titanium Alloys)
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Open AccessArticle
Mechanical Properties and the Microstructure of β Ti-35Nb-10Ta-xFe Alloys Obtained by Powder Metallurgy for Biomedical Applications
Metals 2019, 9(1), 76; https://doi.org/10.3390/met9010076 - 12 Jan 2019
Cited by 1
Abstract
Titanium alloys with high refractory metals content are required to obtain advanced biomaterials with a low elastic modulus and good mechanical properties. This work studies the influence of Fe content on the microstructure and mechanical properties of powder metallurgy Ti35Nb10Ta(Fe) alloys, with Fe [...] Read more.
Titanium alloys with high refractory metals content are required to obtain advanced biomaterials with a low elastic modulus and good mechanical properties. This work studies the influence of Fe content on the microstructure and mechanical properties of powder metallurgy Ti35Nb10Ta(Fe) alloys, with Fe content additions of 1.5, 3.0 and 4.5 wt%. Samples are obtained by uniaxial compaction and sintering at 1250 °C and 1300 °C. Microstructural characterization is performed by scanning and transmission electron microscopy and mechanical characterization by bending, compression and a hardness test. The elastic modulus is measured by the ultrasounds technique. The results show a 10% increase in the maximum bending strength with an increase in the sintering temperature. The obtained microstructure is composed of β-Ti phase (bcc) and some regions where laths of the α-Ti (hcp) phase occur along the grain boundaries. Fe addition slightly improves the stability of the β-Ti phase and conversely decreases the maximum strength and final deformability due to increased porosity. The Ti35Nb10Ta alloy composition displays better properties, with an elastic modulus of 75 GPa, a bending strength of 853 MPa and compression strength of 1000 MPa. Full article
(This article belongs to the Special Issue Powder Metallurgy of Titanium Alloys)
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Open AccessArticle
High-Temperature Compressive Properties of TiB-Reinforced Ti Alloy via In Situ Synthesis
Metals 2018, 8(5), 303; https://doi.org/10.3390/met8050303 - 27 Apr 2018
Cited by 1
Abstract
In this investigation, in situ synthesis of TiB-reinforced Ti-based alloy was carried out by powder metallurgy. The Ti (TiH2)—Al and B powders were ball milled for 40 h to obtain a mixed powder with a nominal composition of Ti-7Al-0.2B (wt. %) [...] Read more.
In this investigation, in situ synthesis of TiB-reinforced Ti-based alloy was carried out by powder metallurgy. The Ti (TiH2)—Al and B powders were ball milled for 40 h to obtain a mixed powder with a nominal composition of Ti-7Al-0.2B (wt. %) and TiH2-7Al-0.2B (wt. %). After milling the mixed powder by using a vacuum hot pressing sintering furnace (1200 °C sintering temperature, 30 MPa pressure, 1 h holding pressure), TiB-reinforced Ti-based alloy was prepared in situ. The compression tests were carried out on a WDW-200 universal testing machine at 550 °C, 600 °C, and 650 °C, and at the strain rates of 1 × 10−4 s−1, 3 × 10−4 s−1, and 5 × 10−4 s−1 to investigate the alloy compression and rheological behavior of the prepared alloy. It was observed that Ti-7Al-0.2B and TiH2-7Al-0.2B alloy formed a TiB phase and α-Ti duplex structure after low-energy ball milling and hot pressed sintering. This is because the in situ synthesis of TiB fiber reinforced phase hinders grain boundary migration and grain growth. Therefore, the TiB phase in Ti-7Al-0.2B alloy is fine, evenly distributed and effective in suppressing grain growth. Alloy materials are heat sensitive and strain-rate sensitive alloys, and the peaks of high-temperature compressive stress decrease with the decrease of the strain rate and the increase of the temperature. At the same temperature and rate conditions, the highest peak flow stress of TiH2-7Al-0.2B is slightly higher than that of Ti-7Al-0.2B. In the ball milling and sintering process of TiH2-7Al-0.2B alloy, the decomposition of H from TiH2 cleanses the surface of Ti particles. This leads to the reduction of the possibility of contamination, and also has a good effect in improving the compression performance. Full article
(This article belongs to the Special Issue Powder Metallurgy of Titanium Alloys)
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Review

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Open AccessReview
Near Net Shape Manufacture of Titanium Alloy Components from Powder and Wire: A Review of State-of-the-Art Process Routes
Metals 2019, 9(6), 689; https://doi.org/10.3390/met9060689 - 15 Jun 2019
Abstract
Near net shape (NNS) manufacturing offers an alternative to conventional processes for the manufacture of titanium alloy components. Compared to the conventional routes, which typically require extensive material removal of forged billets, NNS methods offer more efficient material usage and can significantly reduce [...] Read more.
Near net shape (NNS) manufacturing offers an alternative to conventional processes for the manufacture of titanium alloy components. Compared to the conventional routes, which typically require extensive material removal of forged billets, NNS methods offer more efficient material usage and can significantly reduce machining requirements. Furthermore, NNS manufacturing processes offer benefits such as greater flexibility and reduced costs compared to conventional methods. Processes such as metal additive manufacturing (AM) have started to be adopted in niche applications, most notably for the manufacture of medical implants, where many conventionally forged components have been replaced by those manufactured by AM processes. However, for more widespread adoption of these emerging processes, an improvement in the confidence in the techniques by manufacturers is necessary. This requires addressing challenges such as the limited mechanical properties of parts in their as-built condition compared to wrought products and the post-process machining requirements of components manufactured by these routes. In this review, processes which use a powder or wire feedstock are evaluated to assess their capabilities for the manufacture of titanium alloy components. These processes include powder bed fusion and direct energy deposition metal additive processes as well as hybrid routes, which combine powder metallurgy with thermomechanical post-processing. Full article
(This article belongs to the Special Issue Powder Metallurgy of Titanium Alloys)
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