Optimization of the mechanical properties of Ti-6Al-4V alloy fabricated by selective laser melting using thermohydrogen processes

BILGIN, Guney Mert
Esen, Ziya
Akin, Seniz Kushan
Dericioğlu, Arcan Fehmi
2-step Thermo Hydrogen Process (THP) including hydrogenation and dehydrogenation steps was applied to Ti-6Al-4V alloy fabricated by selective laser melting (SLM) process to refine the microstructure and to increase the ductility of the alloy. It was observed that as-fabricated alloy's surface was composed of oxides of titanium and aluminum, which may alter the hydrogenation kinetics. The hydrogen treatment for 1 hat 650 degrees C, the maximum hydrogen solubility temperature of the alloy, transformed starting non-equilibrium alpha'-martensitic phase to 13 and 8 (TiH2) phases. On the other hand, very fine discontinuous beta-phase was formed along with alpha-phase as a result of dehydrogenation at 700 degrees C for 18 h, which decreased the hydrogen level well below the starting value and caused transformation of delta-phase to fine alpha-phase. In contrast to commonly used THP treatments consisting of betatizing at high temperature, 2-step treatment prevented grain boundary alpha-phase formation as well as excessive grain growth. About 110% and 240% increments were detected in % Elongation (EL) and % Reduction in Area (RA) values, respectively, as a result of 2-step THP, while the strength decrease was limited to 10%. The change in ductility of the alloy was also verified by transformation of flat and shiny fracture surfaces seen in SLM fabricated alloy to a fracture surface containing equiaxed dimples after THP treatment. The hardness drop in the alloy after hydrogenation and dehydrogenation treatments was attributed to relief of residual stress and formation of equilibrium alpha and beta-phases.


Optimization of the mechanical properties of Ti-6Al-4V alloy produced by three dimensional additive manufacturing using termochemical processes
Bilgin, Güney Mert; Durucan, Caner; Esen, Ziya; Department of Metallurgical and Materials Engineering (2017)
Selective laser melting (SLM) is an additive manufacturing (AM) technology used for aerospace and biomedical Ti-6Al-4V alloys to produce parts with complex geometry at one step with reduced production time, scrap and cost. However, parts produced by SLM are lack of ductility due to microstructures similar to those cast products and residual stresses generated during laser processing. In this study, Ti6Al-4V alloys produced by SLM were treated by thermo-hydrogen process (THP) to increase ductility and to ref...
Optimization of conditions to produce manganese and iron carbides from Denizli-Tavas manganese ore by solid state reduction
Akıl, Cem; Geveci, Ahmet; Department of Metallurgical and Materials Engineering (2007)
Main purpose of this study was to find the optimum conditions to produce a charge material for ferromanganese production or steelmaking with high content of iron and manganese carbides from Denizli-Tavas manganese ore by carbothermic reduction and investigate the effects of temperature, time, amount of active carbon addition and CaO addition on this reduction. The ore was calcined and then mixed with active carbon and CaO. Experiments were performed in a horizontal tube furnace that can be heated up to 1700...
Production of Ti-6Al-4V alloy by 3D electron beam melting technique and development of itspost treatments
Doğu, Merve Nur; Dericioğlu, Arcan Fehmi; Department of Metallurgical and Materials Engineering (2019)
In this thesis, the effects of production variables in electron beam melting (EBM) and post-processing on the materials’ and mechanical properties of Ti-6Al-4V alloy were investigated by considering the microstructural change. Ti-alloy samples were produced at 0o, 45o and 90o with respect to building plate. Surface polishing with HF solution was applied to reduce the surface roughness. On the other hand, post-heat treatments, namely, 2-step thermo-hydrogen processing (THP) and annealing, were conducted to i...
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Karaman, Mustafa; Sezgi, Naime Aslı; Doğu, Timur; Ozbelge, H. Onder (2006-12-01)
Production of beta-rhombohedral boron carbide (B4C) on a tungsten substrate by the chemical vapor deposition from a BCl3-H-2-CH4 gas mixture was achieved. An impinging-jet reactor was used to minimize the mass-transfer limitations on the reaction kinetics, which made a detailed kinetic investigation possible. Results of the XRD and XPS analyses showed that the solid product formed on the substrate is a rhombohedral B4C phase. Both dichloroborane and boron carbide formation rates were found to increase with ...
Estimation of Binding Constants of Cd(II), Ni(II) and Zn(II) with Polyethyleneimine (PEI) by Polymer Enhanced Ultrafiltration (PEUF) Technique
Kadioglu, Sezin Islamoglu; Yılmaz, Levent; Ozbelge, H. Onder (Informa UK Limited, 2009-01-01)
Continuous and batch processes of polymer enhanced ultrafiltration for the estimation of binding constants of divalent cadmium, nickel, and zinc ions have been elaborated. Polyethyleneimine was used as a complexation agent. Effect of pH and ionic strength on the binding ability of target metal ions to polyethyleneimine were estimated by continuous mode PEUF system. A mathematical model was developed to estimate apparent complexation constants of metal ions with PEI. The development of this model, which is i...
Citation Formats
G. M. BILGIN, Z. Esen, S. K. Akin, and A. F. Dericioğlu, “Optimization of the mechanical properties of Ti-6Al-4V alloy fabricated by selective laser melting using thermohydrogen processes,” MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, pp. 574–582, 2017, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/33009.