The high cost of Ti alloys is hindering their industrial implementation and, therefore, the quest for low-cost Ti alloys entails lowering the intrinsic cost using cheaper alloying elements and developing more efficient manufacturing methods. In this study, the yield of manufacturing the novel low-cost Ti-5Fe alloy via heat-andhold and cyclic induction sintering around the allotropic alpha ->(3 phase transformation was compared as the latter is expected to enhance densification. It is demonstrated that induction sintering is extremely efficient due to its characteristic high heating rates and simultaneously permits to obtain homogenous chemical compositions at low homologous sintering temperatures. Cyclic sintering yields faster sintering kinetics, which results in higher densification with respect to heat-and-hold, achieving uniform residual porosity distributions within the microstructure, comparable relative density, and on average smaller and more spherical pores. Consequently, higher strength but not necessarily higher ductility is obtained for the cyclic sintered Ti-5Fe alloy as the failure mode entails crack propagation through irregularly shaped pores.

The manufacturing of Ti alloys via powder metallurgy and the development of novel compositions are two strategies to reduce the cost of Ti, which is still the primary factor deterring its wider use in engineering applications. In this study, new Ti alloys based on the combined addition of Sn with Nb, Mo, or Mn are manufactured via powder metallurgy to gain an understanding of the role of these β stabilizers on the performance achievable. It is found that the designed alloys have a fully homogeneous chemistry regardless of their actual composition and a lamellar or β‐type microstructure depending on the actual β stabilizer used. This study confirms that the β‐stabilizing power effect decreases from Mn to Mo and, eventually, Nb. The compressibility and sinterability of the alloys increase with the progressive addition of the selected powders, generally leading to stronger and more ductile materials. It is also found that the proposed Ti‐3Sn‐Mo alloys are characterized by the best strength/ductility pairs compared to a variety of sintered or cast binary/ternary Ti alloys bearing the alloying elements considered in this work.

The combination of low-cost alloying elements like Fe and powder metallurgy, a route with potential to lower the cost of processing titanium alloys, is an interesting option to process cost-effective titanium alloys. Using thermomechanical processing can help improve their behaviour, but limited work has been devoted to it. Additionally, there is a lack of knowledge on their fatigue performance. In this work, different extrusion and heat treatment conditions were applied to develop different microstructures and textures, and their effect on the tensile and fatigue behaviour was thus studied. Small differences in the extrusion and annealing temperatures, when in the α+β phase, result in strong Fe partitioning between α and prior β grains, developing an ultrafine transformed β microstructure instead of lamellar colonies. This results in a remarkable strengthening of the alloy plus an increase in ductility. Despite reaching practically full density after extrusion, residual pores influence the fatigue behaviour (but not the tensile behaviour), and the extent of their influence depends on the intrinsic strength of the alloy. By carefully selecting the thermomechanical processing conditions, the cost-effective powder metallurgy Ti-5Fe alloy can match the fatigue performance of the workhorse Ti-6Al-4V alloy.

In this study, the low-cost Ti-5Fe alloy was fabricated by a combination of sintering plus thermomechanical treatment (TMT). The primary aim is to improve the tensile properties of the recently widely studied powder metallurgy Ti-xFe alloys made by the press and sinter process. The effect of hot forging or extrusion and subsequent annealing treatment on the microstructure and mechanical properties of the Ti-5Fe alloy was therefore studied. TMT from temperatures in the beta-phase field severely changes the microstructure of the sintered alloy. The substantial deformation of the beta-grains and the formation of fine alpha-phase have a significant effect on the mechanical properties. The yield and ultimate tensile strengths of the TMT alloys reach high values, from 1050 MPa to over 1200 MPa. The subsequent heat treatment results in the modification of the alpha-phase morphology and the partial loss of the crystallographic texture, leading to the enhancement of the elongation to values above 20%, despite of the high oxygen content of the alloy.

Powder metallurgy Ti alloys are commonly processed via vacuum sintering, which is a lengthy and energy intensive process that contributes to the high cost of the final product. In this comparative study, we demonstrate that induction sintering, where consolidation of blended elemental Ti alloys is achieved by means of high-frequency induction heating, is a promising alternative to consolidate both wrought-equivalent (Ti–6Al–4V and Ti–3Al–2V) and low-cost Fe-bearing (Ti–5Fe and Ti–5SS) powder metallurgy Ti alloys more efficiently. It is found that high relative density values and chemical homogeneity are achieved regardless of the sintering technique or chemistry of the alloy. With respect to vacuum sintered materials, the induction sintered alloys have slightly lower relative density, finer microfeatures, lower oxygen content and comparable tensile behaviour, making them suitable candidates for structural engineering products manufactured at lower cost. With the right processing parameters, low-cost Fe-bearing powder metallurgy Ti alloys have comparable properties to those of wrought-equivalent alloys where cost reduction is obtained via reducing the intrinsic cost of the material.

A powder metallurgy approach was applied for the synthesis of an alpha + beta Ti-2Al-3Fe alloy. Blends of the elemental Ti, Al and Fe powders were compacted and subsequently sintered. High-frequency induction heating (HFIH) instead of conventional high-vacuum furnace heating was used for the sintering, due to its high efficiency. The effect of temperature on the level of densification, residual porosity and mechanical properties was studied. Electron dispersive spectrum analysis was used to study the dissolution and homogenization of the alloying elements. The results showed that a short induction sintering (IS) cycle in the range of 10-15 min is sufficient to achieve significant powder consolidation, evident by the increase of the density and mechanical properties. The residual porosity diminishes with the increase of the sintering temperature. Full dissolution of the alloying powders is completed after sintering at temperatures above those of alpha- to beta-phase transformation.

Ti alloys, generally made via wrought metallurgy, are commonly used as biomedical materials. The manufacturing of such alloys via powder metallurgy offers the possibility to reduce the cost as well as to develop innovative compositions not otherwise achievable. The aim of this study is to understand the effect that the progressive addition of Al has on the physical and mechanical behaviour of the low-cost powder metallurgy Ti-5Fe alloy for structural biomedical implants. Specifically, Ti-5Fe-xAl (x = 1-6 w.%) alloys were developed combining blending elemental and cold pressing plus vacuum sintering to further limit the manufacturing costs as Al is lighter and cheaper than Ti. This investigation demonstrates that the amount of Al added significantly changes the thermodynamics of the sintering process and induces microstructural modifications such as grain refinement. These effects jointly with the Al solid solution strengthening leads to progressively stronger and harder (but less ductile) alpha+beta Ti alloys characterised by the typical alpha+beta lamellar microstructure with mechanical behaviour suitable for a variety of structural biomedical implants.

Pure Ti is characterised by an interesting combination of performance from an engineering point of view. The addition of Al to Ti can be used to reduce the intrinsic cost of the material, decrease the density of the alloy, and increase the mechanical performance. This study is focused on evaluating the physical properties, microstructural evolution and mechanical behaviour of Ti-xAl alloys (where x = 1-6 wt%) in order to scientifically understand the strengthening mechanisms of the addition of Al to pure Ti manufactured via the conventional powder metallurgy route of cold uniaxial pressing plus solid state sintering. The addition of Al to Ti does not affect the compressibility of the alloy but changes the consolidation and densification of the alloy. The incremental addition of Al results in the progressive strengthening of Ti via the simultaneous contribution from substitutional solid solution and grain refinement strengthening which outdo the negative effect of the residual porosity. (C) 2019 Elsevier B.V. All rights reserved.

Cost reduction of Ti alloys is paramount to open up new industrial opportunities and the powder metallurgy blended elemental approach is ideal for such endeavour. Although faster, microwave sintering is a pressureless sintering process and leaves behind residual porosity which lowers the mechanical performance limiting the applicability of the material. Work hardening and porosity sealing of microwave sintered blended elemental Ti alloys via thermomechanical deformation by means of hot extrusion in the β field was thus investigated. As expected, the chemistry and the thermal history of each alloy considered (i.e. pure Ti, Ti-6Al-4V, and Ti-5Fe) has an influence on the microstructure and mechanical performance. However, regardless of those two aspects, hot extrusion permits to obtain fully dense materials with enhanced mechanical behaviour due to the reduction of the residual pores and microstructural modification such as formation of lamellar substructures resulting in alloys with better strength/ductility pairings and, therefore, different strain hardening rates and deformation modes.

The article “Advancement in the Pressureless Sintering of CP Titanium Using High-Frequency Induction Heating”, written by Stella Raynova, Yan Collas, Fei Yang, and Leandro Bolzoni was originally published Online First without Open Access. After publication in volume 50A, issue 10, page 4732 the author decided to opt for Open Choice and to make the article an Open Access publication. Therefore, the copyright of the article has been changed to © The Author(s) 2019 and the article is forthwith distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits use, duplication, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made

Ti alloys are the ideal material fora great range of applications but their industrial implementation is hindered by current technological and manufacturing limitations. This work presents the scientific development of an emerging alternative route to manufacture Ti alloys from particulate materials. Experimental evidences to show that the proposed manufacturing route, which takes advantage of the benefits of particulate processing, permits to obtain structurally sound Ti alloys using much shorter production routines removing some of the technological and manufacturing limitations hindering the use of Ti alloys in engineering applications are presented. It is found that the relative density increases with the sintering temperature reaching values around 93% and dissolution of the alloying elements is complete. The mechanical properties of the produced representative blended elemental alpha +/- beta Ti alloy also increase with the temperature reaching a maximum ultimate tensile strength of 850 MPa. (C) 2020 Elsevier B.V. All rights reserved.

In this study the low-cost Ti-5Fe alloy was fabricated by means of the press and sinter powder metallurgy route considering two particle sizes and alternative processing techniques. The primary aim is to reduce the high costs associated with the production of Ti alloys. Thermomechanical processing by means of forging in the β region was also analysed aiming to enhance the mechanical behaviour. The effect of the processing conditions and of the particle size on the microstructure and the mechanical properties was thus investigated. It has been found that the use of larger Fe particles leads to the formation of larger pores due to the dissolution of the Fe powder particles. Consequently, lower mechanical behaviour, tensile properties and Vickers hardness, resulted due to the presence of larger pores. Refinement of the microstructure, texturing, and sealing of the porosity due to forging permits to enhance the mechanical properties with respect to the sintered Ti-5Fe alloy.

Ti-6Al-4V (Ti-64) swarf is produced every day in commercial operations but its direct use for the fabrication of strong and ductile Ti-6Al-4V alloy is seldom reported. This study consolidated as-received Ti-64 swarf into near fully dense Ti-6Al-4V alloy by hot pressing. The microstructures and tensile mechanical properties of the hot-pressed Ti-64 alloy and the effect of subsequent solution treatment and ageing (STA) were studied. The hot-pressed Ti-64 achieved tensile yield strength (TYS) of 928–998 MPa, ultimate tensile strength (UTS) of 1076–1139 MPa and strain to fracture of 6.92–7.80%. The STA increased the TYS to 1103–1143 MPa and UTS to 1188–1223 MPa, accompanied by a decline in the strain to fracture to 5.32–6.48%. These tensile property data suggest that it is possible to directly consolidate Ti-6Al-4V swarf into a strong and ductile Ti-6Al-4V alloy by hot pressing for a variety of potential applications.

Powder metallurgy Ti-Fe alloys are of growing interest due to their low cost and good mechanical behaviour, which is comparable to that of the workhorse Ti-6Al-4V. Fe is normally added as alloying element to develop alpha+beta alloys characterised by the typical lamellar structure. In this work, treating the alloy as metastable beta-Ti, the slow bainitic transformation has been used to enable the formation of ultrafine alpha+beta microstructures in a powder metallurgy Ti-5Fe alloy, achieving superior properties. The kinetics for the formation and decomposition of the phases was studied to achieve different microstructures. alpha-Ti is formed at temperatures as low as 400 degrees C in less than 24 h, while omega-Ti is stable up to 450 degrees C. In this case, the high oxygen typical of low cost PM alloys manufactured using hydride-dehydride powder made a positive contribution by stabilising alpha-Ti over omega-Ti in shorter times and at lower temperatures. (c) 2018 Elsevier B.V. All rights reserved.

Sintering is a vital technology used for consolidation of metal and ceramic powders. The process is generally long and energy consuming because of the way in which heat transfer happens in electrical and gas furnaces. This study focuses on optimizing the sintering process of metallic powders, in particular titanium, using high frequency induction heating as alternative sintering method. Using electromagnetic induction and the associated Eddy current effect, the heat is generated directly into the electrically conductive object. Consequently, faster heating rates and lower heat loses are achieved. The purpose of this study is to understand the effect of process parameters, such as the powder compact density, on the efficiency of the induction heating and the properties of the sintered materials. The average heating rates recorded while heating to 1300oC are in the range of 3.5o to 15.3o C per second. Significant densification and consolidation, evident by the amount of closed porosity and increase in tensile strength was found in spite of the short heating time. The results show that the powder compact density plays a crucial role on the heating efficiency as well on the properties of the sintered material such as final density, porosity distribution and tensile properties. The samples with higher initial density showed tensile strength and ductility values comparable to those of high vacuum sintered and those specified by international standards for powder metallurgy Ti products.

Powder metallurgy is a very attractive method for producing titanium alloys, which can be near-net-shape formed and have freedom in composition selection. However, applications are still limited due to product affordability. In this paper, we will discuss a possible cost-effective route, combining fast heating and hot processing, to produce titanium alloys with similar or even better mechanical properties than that of ingot metallurgy titanium alloys. Two titanium alloys, Ti-5Al-5V-5Mo-3Cr (Ti-5553) and Ti-5Fe, were successfully produced from HDH titanium powder and other master alloy powders using the proposed processing route. The effect of the processing route on microstructural variation and mechanical properties have been discussed.

A trace amount of LaB6 powder was added to P/M Ti and Ti–6Al–4V alloy to improve mechanical properties and refine the microstructure. After sintering, TiB whiskers and La2O3 dispersoids had formed in the microstructure. In a CP Ti alloy, the generation of secondary phases leads to a much refined microstructure, but the alignment of TiB whiskers led to a variation in mechanical properties. Open die forging (ODF) or powder compact extrusion (PCE) was carried out on sintered Ti–6Al–4V alloy to further improve the mechanical properties. This caused severe deformation and re-alignment of the TiB whiskers. Comparing the properties of hot worked Ti–6Al–4V alloy and Ti–6Al–4V alloy with boron additions, an addition of LaB6 leads to slightly lower strength but gives significant better ductility.

Powder forging is a recently developed manufacturing process to produce low cost titanium components with superior properties. Conventional P/M techniques such as compaction and sintering have proved inadequate for producing dense and high performance titanium components, while forging still remains a primary process in the manufacturing of high performance titanium components. A numerical simulation of powder compact forging would increase our understanding of the flow behaviour of material in the forging die. In this study, a 2D FEM coupled thermal displacement model was used for analysing deformation and densification of a powder compact during upset forging. Simulations were performed using the Gurson and Gurson-Tvergaard material models, to predict the densification behaviour at three different forging temperatures and the results were compared with radio-graphically obtained density results. The influence of parameters such as friction, heat transfer and material flow is discussed with respect to relative density.

Er powder with a very large particle size was added to Ti metal and Ti–6Al–4V alloy to achieve a supersolidus liquid sintering effect. However, instead of promoting sintering and homogenisation, very big worm-like voids were created by a substantial Er–Ti liquid phase. Such voids were surrounded by Er segregation and made tensile testing of a Ti–Er alloy impossible. An open die forging process was then employed to diminish these pores and homogenise the Er distribution. Fine Er spots or acicular textures were found in the matrix, but some Er segregation still persisted. The material is weakened by segregation. Good mechanical properties are obtained when the testpieces have reduced levels of Er segregation. Further work will be focused on the homogenisation of Er.

Ti–6Al–4V (wt%) bar and disk with a density close to 100%, a lamellar structure and oxygen content of 0.44 and 0.51wt%, respectively, have been made by powder compact extrusion and powder compact forging of HDH Ti–6Al–4V powder respectively. Their microstructure, tensile mechanical properties at different strain rates in the range of 10−4–10−1s−1 and the fracture surfaces and longitudinal sections of the tensile test specimens have been studied. It was found that the level of consolidation of the PE/Ti–6Al–4V bar and PF/Ti–6Al–4V disk was very high, as reflected by their high strength and good ductility, small untransformed interparticle boundaries (smaller than 3μm in sizes), and low volume fraction of cavities (<1.5%) formed by separation of powder particles at the untransformed interparticle boundaries in the specimens tensile tested at a high strain rate of 10−2s−1. The high level of consolidation achieved within a short time through induction heating and extrusion/forging of the Ti–6Al–4V powder compacts suggests that the rate of transforming interparticle boundaries to grain boundaries is very high, and the reasons for this might be formation of new powder particle surfaces through plastic deformation and rapid dissolution of the powder particle surface oxide films. The formation of cavities from the untransformed interparticle boundaries in the PE/Ti–6Al–4V bar and PF/Ti–6Al–4V disk is highly strain rate sensitive with the number and volume fraction of the cavities formed increases significantly with increasing the strain rate.