Microstructural evolution and mechanical properties of in-situ as-cast beta titanium matrix composites

[EN] The aim of this research is to investigate the effects of B4C additions on microstructure refinement and mechanical properties, due to in-situ formation of TiB and TiC in a matrix of beta titanium by casting process. Researches have been done on the individual effects of TiC and TiB compounds in titanium composites, however, their hybrid effect has been scarcely explored in beta titanium alloys. The effects on lattice parameter were investigated by Rietveld refinement and EDS analysis. The beta lattice parameters increased due reaction between Ti and B4C. DTA analysis revealed the sequence of phase formation on heating and cooling around the melting point, being confirmed by investigation of orientation relationship between phases by EBSD and pole figure analysis. Orientation relationships are {312}(TiB)//{112}(beta), {112}(TiC)//{112}(beta) for the smallest addition of B4C, {113}(TiC)//{112}(beta) for the remaining composites, and {010}(Ti)(B)//{011}(T)(i)(c) between the particles. Grain size reduced by half with 0.5% addition of B4C, while 3% addition made grains 25 times smaller than the alloy. Young's modulus and hardness increased with the addition of boron carbide. An analysis of the hardness of the materials was carried out from a nano to a macro scale. The as-cast composite materials have a refined structure with improved mechanical properties in comparison to the commercial alloy. (C) 2018 Elsevier B.V. All rights reserved.The authors gratefully acknowledge the Brazilian research funding agencies CNPq (National Council for Scientific and Technological Development) and CAPES (Federal Agency for the Support and Evaluation of Graduate Education) for their partial financial support of this work.Rielli, VV.; Amigó, V.; Contieri, RJ. (2019). Microstructural evolution and mechanical properties of in-situ as-cast beta titanium matrix composites. Journal of Alloys and Compounds. 778:186-196. https://doi.org/10.1016/j.jallcom.2018.11.093S18619677

Selective Laser Melting of Ti-6Al-4V Alloy: Correlation Between Processing Parameters, Microstructure and Corrosion Properties

Additive Manufacturing technology has continually advanced, allowing microstructure and property optimization. In recent years, several studies have been carried out with the aim of understanding mechanisms of formation and evolution of the microstructure and, consequently, their influence on mechanical properties. However, correlations between microstructure and corrosion properties are not completely understood, making more systematic investigations necessary. In this work, samples of the Ti-6Al-4V alloy were produced by combining different laser powers and scanning speeds in order to generate different energy density values (VED) with subsequent microstructures and properties. The samples were characterized by optical and scanning electron microscopy, hardness and relative density. Complementarily, corrosion tests were carried out. For the entire set of parameters used, the processed samples showed the formation of acicular martensite α´, followed by different levels of porosity depending on the applied energy density. VED proved to be an important control parameter, and the best combinations of hardness and corrosion resistance were obtained for the parameter ratio that generated energy densities greater than 100 J/mm3

Single step heat treatment for the development of beta titanium composites with in-situ TiB and TiC reinforcement

[EN] Titanium matrix composites have been attracting great interest from aerospace industry due to favorable properties like thermal stability, high specific strength, corrosion, and wear resistance. Optimal relation between mechanical properties demands complex processing routes and, in this context, the effects of a single-step processing route on microstructure and mechanical properties of ß titanium matrix composites was placed on focus in this study. The commercial TIMETAL Beta 21S alloy and its modification with the addition of B4C were developed, allowing in-situ formation of TiB and TiC particles in a ß matrix. The composites presented highest values of mechanical strength and hardness, and the addition of 3% of B4C provided a significant reduction in grain size, and compressive yield strength and ultimate compressive strength values of 1205 MPa and 1636 MPa, respectively, with a maximum deformation of 20.5%. An orientation relationship investigation provided in- formation about some unconventional relation between the present phases.The authors are grateful for the funding provided by the Brazilian research agencies FAPESP (State of Sao Paulo Research Foundation) and CAPES (Federal Agency for the Support and Evaluation of Graduate Education). The authors also gratefully acknowledge the use of experimental facilities at Brazilian Nanotechnology National Laboratory (LNNano), and the Electron Microscopy Service and Materials Technology Institute at the Universitat Politecnica de Valencia.Rielli, VV.; Amigó, V.; Contieri, RJ. (2020). Single step heat treatment for the development of beta titanium composites with in-situ TiB and TiC reinforcement. Materials Characterization. 163:1-10. https://doi.org/10.1016/j.matchar.2020.11028611016

Effects of Sn addition on the microstructure, mechanical properties and corrosion behavior of Ti–Nb–Sn alloys

Ti and Ti alloys are widely used in restorative surgery because of their good biocompatibility, enhanced mechanical behavior and high corrosion resistance in physiological media. The corrosion resistance of Ti-based materials is due to the spontaneous formation of the TiO2 oxide film on their surface, which exhibits elevated stability in biological fluids. Ti–Nb alloys, depending on the composition and the processing routes to which the alloys are subjected, have high mechanical strength combined with low elastic modulus. The addition of Sn to Ti–Nb alloys allows the phase transformations to be controlled, particularly the precipitation of ω phase. The aim of this study is to discuss the microstructure, mechanical properties and corrosion behavior of cast Ti–Nb alloys to which Sn has been added. Samples were centrifugally cast in a copper mold, and the microstructure was characterized using optical microscopy, scanning electron microscopy and X-ray diffractometry. Mechanical behavior evaluation was performed using Berkovich nanoindentation, Vickers hardness and compression tests. The corrosion behavior was evaluated in Ringer's solution at room temperature using electrochemical techniques. The results obtained suggested that the physical, mechanical and chemical behaviors of the Ti–Nb–Sn alloys are directly dependent on the Sn content96273281CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP484379/2012-72011/23942-6The authors gratefully acknowledge the Brazilian research funding agencies FAPESP (State of São Paulo Research Foundation) Grant # 2011/23942-6, CNPq Grant # 484379/2012-7 (National Council for Scientific and Technological Development) and CAPES (Federal Agency for the Support and Evaluation of Graduate Education) for their financial support of this wor