The effect of Zr and Sn additions on the microstructure of Ti-Nb-Fe gum metals with high elastic admissible strain

An open challenge on structural biomaterials is to obtain low-cost Ti-alloys with high elastic admissible strength (the ratio of yield strength to modulus). To reach this goal, we designed and characterized three quaternary alloys from the Ti-Nb-Fe system with additions of Zr and Sn. The samples were solution-treated and tested under two conditions: water-quenched and aged at 450 °C. Microstructures were analyzed with aid of scanning and transmission electron microscopy. Tensile tests performed at room-temperature confirmed a remarkable yield strength of 1271 MPa with an elastic modulus close to 90 GPa among aged Ti-19Nb-2.5Fe-6Sn (wt%) samples. Solution-treated Ti-19Nb-2.5Fe-10Zr samples presented a good combination of yield-strength and elastic modulus (1027 MPa and 69 GPa, respectively), displaying an elastic admissible strength close to 1.5. Although Zr and Sn are equally distributed between matrix and precipitates, the diffusion of Nb and Fe seem to be inhibited by the presence of Sn. As a result, Sn allows higher yield-strengths and more refined secondary α-phase, while Zr has a stronger effect on reducing the elastic modulus. In the end, a materials selection chart is presented to help designers to select materials for orthopedic implants considering the elastic admissible strain and cost as major guidelines16011861195CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPNão tem2014/24449-0; 2016/22714-3; 2016/24693-3Funding: This work was supported by FAPESP (São Paulo State Research Foundation, grants numbers 2014/24449-0, 2016/22714-3 and 2016/24693-3) and CNPq (National Council for Scientific and Technological Development). The authors gratefully acknowledge Prof. Hamish Fraser for the use of experimental facilities at the Center for Electron Microscopy and Analysis (CEMAS), at the Ohio State University, USA, and thank CBMM Co. for the Nb supply. The raw/processed data required to reproduce these findings cannot be shared at this time as the data also forms part of an ongoing study. Data will be made available upon reques

Formation of alpha phase via pseudospinodal decomposition in Ti-Nb-Fe based alloys

Herein, the fine-scaled α phase precipitation during step-quench heat treatments in Ti‐15Nb‐3.0Fe and Ti‐11Nb‐3.5Fe (wt%) alloys was evaluated. Thermodynamic analyses suggest that Ti‐11Nb‐3.5Fe alloy should present homogenous α phase formation via the pseudospinodal mechanism when solution-treated and step-quenched at 450 °C, which is confirmed in this work. STEM-EDX measurements confirm the non-equilibrium state of the α phase precipitates, whose Nb content is significantly higher than that of the α phase laths obtained after solution heat treatment followed by furnace cooling. Fe seems to play an important role in the precipitation mechanism, and is depleted from α phase laths in a short aging time189201205FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP2014/24449-0; 2014/06099-1This work was supported by FAPESP (grants numbers 2014/24449-0 and 2014/06099-1). The authors acknowledge the Brazilian Nanotechnology National Laboratory (LNNano) at CNPEM, Brazi

Orthorhombic martensite formation upon aging in a Ti-30Nb-4Sn alloy

The characteristics of orthorhombic martensite (α″) formed by step-quenching in a Ti-30Nb-4Sn (wt%) alloy have been investigated by transmission electron microscopy (TEM) and X-ray diffraction (XRD). According to literature, α″ lattice parameters depend mainly on the composition of the parent β phase. In this study, samples subjected to step quenching heat treatment presented α″ phase formation in the proximity of α phase laths, driven by two combined factors: solute rejection and lattice strain. Our results indicate that as the aging is prolonged, α″ becomes richer in solute content, which makes it more similar to the parent β phase. An average 2.55% lattice strain along [110]β directions was found to be necessary in order to obtain α″ from the β phase after 24 h of aging at 400 °C, followed by water-quenching. The initial lattice strain along the same direction was estimated at approximately 3.60% with zero aging time. The precipitation of the α phase does not inhibit a solute rich α″ phase formation183238246CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP484379/2012-72012/10164-8; 2013/50391-6The authors gratefully acknowledge the Brazilian research funding agencies FAPESP (#2012/10164-8 and #2013/50391-6) and CNPq (#484379/2012-7) for their financial support; Companhia Brasileira de Metalurgia e Mineração (CBMM) for the Niobium supplied and also the Brazilian Nanotechnology National Laboratory (LME/LNNano/CNPEM) and OSU (The Ohio State University) for the use of electron microscopy facilities and the technical support during the TEM wor

Alpha phase precipitation in Ti-30Nb-1Fe alloys – phase transformations in continuous heating and aging heat treatments

Microstructure and mechanical properties of β metastable Ti-30Nb and Ti-30Nb-1Fe alloys subjected to different aging heat treatments were investigated. Various temperatures and heating rates were employed in order to determine their influence on α phase precipitation. The alloys were characterized by means of differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning and transmission electron microscopy. Several mechanical properties were evaluated, such as Vickers hardness and elastic modulus, and tensile tests were also performed. The results indicate that the addition of Fe reduces the α phase precipitation and ω dissolution temperatures, although ω phase was still detected in Ti-30Nb-1Fe aged at 400 °C. The addition of Fe caused refinement of α phase precipitates, probably due to the higher diffusion coefficient of Fe. As for the influence of the heating rate, 2 and 30 °C/min did not cause significant microstructural changes. Finally, α phase refinement in Ti-30Nb alloy was favored by aging at 550 °C, at a heating rate of 600 °C/min677222229CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPNão temNão tem2013/13867-2; 2014/06099-1The authors gratefully acknowledge the financial support of the Brazilian research funding agencies CAPES (Federal Agency for the Support and Improvement of Higher Education), CNPq (National Council for Scientific and Technological Development) and FAPESP (São Paulo Research Foundation) (Grants #2013/13867-2 and #2014/06099-1

Solute lean ti-nb-fe alloys : an exploratory study

In this study, we explored the Ti-Nb-Fe system to find an optimal cost-effective composition with the lowest elastic modulus and the lowest added Nb content. Six Ti-(31-4x)Nb-(1+0.5x)Fe ingots were prepared and Nb was substituted with Fe, starting at Ti-31Nb-1.0Fe and going up to Ti-11Nb-3.5Fe (wt%). The ingots were subjected to cold rolling, recrystallization and solution treatment, followed by water-quenching (WQ), furnace cooling (FC) or step-quenching to 350 °C, which caused massive formation of isothermal ω phase. All the water-quenched alloys displayed athermal ω phase, which is apparently the result of fully collapsed β phase. The Fe content improved the compressive strength of the alloys. In the FC alloys, substitution with Fe favored the formation of α phase instead of ω phase, giving rise to a solute-rich β phase with a lattice parameter of 0.3249 nm. Among the FC alloys, the lowest modulus of 83±4 GPa was obtained in the Ti-19Nb-2.5Fe alloy, which exhibited fine and well dispersed α precipitation and absence of ω phase. DSC experiments indicated that the experimental alloys showed varying phase stability during heating65761769FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP2014/24449-0; 2014/06099-1This research was funded by FAPESP (São Paulo State Research Foundation) through Grants 2014/24449-0 and 2014/06099-1. All the microscopy work was carried out at the LNNano/CNPEM facilities. The authors thank the company CBMM for supplying the niobium used in this wor

α phase precipitation and mechanical properties of Nb-modified Ti-5553 alloy

Metastable β Ti alloys can be strengthened by controlling α phase precipitation during aging heat treatments. An example of this is Ti-5553 alloy (Ti-5Al-5Mo-5V–3Cr-0.5Fe wt%), which has been extensively applied in the aerospace industry due to its high strength-to-weight ratio. The substitution of V with Nb in Ti-5553 enhances the alloy's hardenability and may alter the mechanisms of α phase precipitation, thereby affecting its mechanical properties. Accordingly, the aim of this study was to evaluate the α phase precipitation and mechanical behavior of Nb-modified Ti-5553. Samples were prepared by arc melting and hot working by swaging, and then subjected to HT1 (solution heat-treated above β transus and aged at 600 °C for 600 min) or HT2 (heat-treated at temperatures below β transus, air cooled, heated to 600 °C and aged for 600 min). Compared to the base Ti-5553, the Nb-modified alloy exhibited improved mechanical strength in the HT1 condition due to nonhomogeneous α phase precipitation, but lower ductility in both aging conditions. An examination of the fracture surface revealed that the substitution of V with Nb did not change the fracture behavior and all the samples showed a quasi-cleavage fracture mode with some evidence of intergranular features. The Ti-5553 samples subjected to HT1 presented more dimples and hence, higher ductility. On the other hand, the HT2 samples showed fracture surfaces with predominantly transgranular features. Lastly, with regard to the pseudospinodal mechanism in the Nb-modified alloy, it was found that the substitution of V with Nb reduces the temperature at which pseudospinodal decomposition occurs by roughly 75 °C670112121CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPNão temNão temThe authors gratefully acknowledge the Brazilian research funding agencies FAPESP (São Paulo Research Foundation) and CNPq (National Council for Scientific and Technological Development) for their financial support, CBMM Co. for supplying Nb, and Prof. Hamish L. Fraser for the use of the FIB/TEM facilities at CEMAS/Ohio State Universit

Brazilian Flora 2020: Leveraging the power of a collaborative scientific network

International audienceThe shortage of reliable primary taxonomic data limits the description of biological taxa and the understanding of biodiversity patterns and processes, complicating biogeographical, ecological, and evolutionary studies. This deficit creates a significant taxonomic impediment to biodiversity research and conservation planning. The taxonomic impediment and the biodiversity crisis are widely recognized, highlighting the urgent need for reliable taxonomic data. Over the past decade, numerous countries worldwide have devoted considerable effort to Target 1 of the Global Strategy for Plant Conservation (GSPC), which called for the preparation of a working list of all known plant species by 2010 and an online world Flora by 2020. Brazil is a megadiverse country, home to more of the world's known plant species than any other country. Despite that, Flora Brasiliensis, concluded in 1906, was the last comprehensive treatment of the Brazilian flora. The lack of accurate estimates of the number of species of algae, fungi, and plants occurring in Brazil contributes to the prevailing taxonomic impediment and delays progress towards the GSPC targets. Over the past 12 years, a legion of taxonomists motivated to meet Target 1 of the GSPC, worked together to gather and integrate knowledge on the algal, plant, and fungal diversity of Brazil. Overall, a team of about 980 taxonomists joined efforts in a highly collaborative project that used cybertaxonomy to prepare an updated Flora of Brazil, showing the power of scientific collaboration to reach ambitious goals. This paper presents an overview of the Brazilian Flora 2020 and provides taxonomic and spatial updates on the algae, fungi, and plants found in one of the world's most biodiverse countries. We further identify collection gaps and summarize future goals that extend beyond 2020. Our results show that Brazil is home to 46,975 native species of algae, fungi, and plants, of which 19,669 are endemic to the country. The data compiled to date suggests that the Atlantic Rainforest might be the most diverse Brazilian domain for all plant groups except gymnosperms, which are most diverse in the Amazon. However, scientific knowledge of Brazilian diversity is still unequally distributed, with the Atlantic Rainforest and the Cerrado being the most intensively sampled and studied biomes in the country. In times of “scientific reductionism”, with botanical and mycological sciences suffering pervasive depreciation in recent decades, the first online Flora of Brazil 2020 significantly enhanced the quality and quantity of taxonomic data available for algae, fungi, and plants from Brazil. This project also made all the information freely available online, providing a firm foundation for future research and for the management, conservation, and sustainable use of the Brazilian funga and flora