Effect of Solution Annealing on Plasma Weld Deposited Ti-6Al-4V Characterized by In-Situ Tensile PDF
Preview Effect of Solution Annealing on Plasma Weld Deposited Ti-6Al-4V Characterized by In-Situ Tensile
Effect of Solution Annealing on Plasma Weld Deposited Ti-6Al-4V Characterized by In-Situ Tensile Testing Combined With EBSD Erlend Næss Trøan Materials Science and Engineering Submission date: June 2014 Supervisor: Ola Jensrud, IMTE Co-supervisor: Jarle Hjelen, IMT Martin Borlaug Mathisen, Norsk Titanium Norwegian University of Science and Technology Department of Materials Science and Engineering Preface This work has been carried out at the Norwegian Univeristy of Science and Technology (NTNU), at the Department of Materials Science and engineering, as a master thesis within Material development and properties. I would like to express my gratitude to my supervisor Ola Jensrud for very good guidance throughout the duration of this project. I would also like to thank my co-supervisor Jarle Hjelen, for many productive talks. In addition, my sincere thanks goes to my company contact at Norsk Titanium, Martin Borlaug Mathisen, for very helpful guidance along the way. Trondheim, June 2014 Erlend Næss Trøan i ii Acknowledgements My sincere thanks go out to the following persons who have guided and helped me throughout the work of my master thesis. Ola Jensrud (NTNU) Supervisor Jarle Hjelen (NTNU) Co-supervisor Martin Borlaug Mathisen (NTi) Company Supervisor Yingda Yu (IMT) Engineer at SEM lab Trygve Schanche (NTNU) Labassistant Torild Krogstad (NTNU) Labassistant Robert Karlsen (NTNU) Cutting of samples Knut Erik Snilsberg (SINTEF) Working with titanium at SINTEF Raufoss Manufacturing Rene de Kloe (EDAX) Engineer in EDAX (producer of OIM Analysis) Eli Beate Larsen (NTNU) Dilatometer Delphine Leroy (NTNU) ReSiNa furnace Wilhelm Dall (SINTEF) Senior engineer at SINTEF Astrid Salvesen (NTNU) Coordinator at the glassblowing workshop I would also like to dedicate my thanks to Norsk Titanium and SINTEF Raufoss Manufacturing for supplying material and data related to the process and tensile test. iii iv Abbreviations list AC Air-cooled AM Additive manufacturing BCC Body centered cubic BOR Burgers orientation relationship CAD Computer aided design CI Confidence index CP Commericially pure CRSS Critical resolved shear stress EBSD Electron backscatter diffraction FC Furnace-cooled HCP Hexagonal close packed IPF Inverse pole figure IQ Image quality NTi Norsk Titanium ROI Region of interest SE Seconday electrons SEM Scanning electron microscope SiC Silicon carbide TEM Transmission electron microscope v vi Abstract This work is based on the work done by Mathisen et al. [1], which considers the mechanical properties of the components produced by Norsk Titanium (NTi). NTi produces Ti-6Al-4V (grade 5 titanium) components by additive manufacturing (AM). After receiving samples from NTi, the material were heat-treated in order to study the possible differences in deformation mechanisms. The material was either furnace-cooled (FC) or air-cooled (AC) after solution annealing at 950°C for 1 hour. Both FC and AC samples went to an aging procedure at 600°C for two hours after solution annealing. The deformation mechanisms were observed by doing in-situ tensile tests with electron-backscattered diffraction (EBSD). The time spent on sample preparation for EBSD proved valuable as the average CI-, fit- and IQ-values for the tensile specimens before deformation were 0.44, 1.07 and 144.8 respectively. Both prismatic and basal slip are present in the material, in addition to hard/soft-grain deformation. The combination of elastic stiffness and Schmid factor proved effective for calculating the activation and propagation of all three types of deformation. In the as-received material, the deformation accumulates at the columnar β-grain boundaries, while after heat treatment, the deformation are more uniformly distributed among the β-grains. The anisotropy of the material is however still obvious, as the deformation is concentrated in certain grain. The AC material gained a more homogenous width of α-lamellas as compared to the as-received material, although tendencies towards basketweave structure were still present. The FC material obtained α-lamellae that are more discontinuous than in the as-received material. The larger the width of the α-lamellas, the higher the ductility, as slip can propagate longer. If the slip isn’t restricted by the orientation of the neighboring lamellas, the material can travel even further. Due to a strict orientation relationship, the material doesn’t seem to obtain a more isotropic texture after the heat treatment. Due to a non-equilibrium composition and microstructure in the AM material, the use of dilatometry was unable to obtain any useful data to determine the transition temperature. The first specimens that underwent a heat treatment showed a very brittle behavior, as the material had been exposed to a contamination of both hydrogen and oxygen. This underlines the importance of atmospheric protection when operating with titanium at elevated temperatures. vii viii
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